5    Ophthalmologic Evaluation and Management

Core Messages

Introduction

The sellar region represents not only the center of the skull base but also the primary ophthalmologic conjunction. Both the afferent visual pathways, represented by the two optic nerves, chiasm, and optic tract, and the efferent visual pathways, including the third, fourth, and sixth cranial nerves, course either above or lateral to the sella. It is thus not surprising that pathology affecting the sellar and parasellar region often presents with ophthalmic manifestations,1–13 and any intervention, be it medical, surgical, or radiologic, can produce its own set of ophthalmic complications^14,15

From an ophthalmic point of view, it is important to recognize the visual system in three parts. The afferent system can be thought of as a mapping function, taking the outside world into our consciousness. To perform this function adequately, the anterior segment of the eye needs to refract (bend and focus) light onto the photosensitive retina, which then converts the electromagnetic radiation into a series of impulses. These impulse signals are conducted via the optic nerves and visual pathways back to the cortex, where interpretation takes place. Interruption anywhere along these pathways can result in symptoms of afferent system dysfunction, including decreased vision, blurred vision, and visual field defects.

The efferent system, responsible for coordinating ocular motility, provides globe movement through the final common pathways of the six extraocular muscles. These are innervated by the third, fourth, and sixth cranial nerves, which travel through the cavernous sinus lateral to the wall of the body of the sphenoid and enter the orbit through the superior orbital fissure. Involvement of these cranial nerves can result in loss of ocular motility, manifested as double vision, blurred vision, or a sensation of spontaneous ocular motility.

Finally, the globe is supported by the orbital tissues making up the adnexal structures. These include the eyelids, responsible for maintaining and distributing an adequate tear film over the cornea, which forms the first part of the refracting surface of the eye. Adnexal tissues also include the lacrimal glands, the accessory lacrimal glands, and the structures responsible for opening and closing the eyes. Any involvement of the innervation of these structures can also result in various ophthalmic symptoms, including pain, numbness, loss of vision, problems with acuity, and double vision. Direct involvement of the orbital structures due to invasion of the orbit, either through the fissures and foramina connecting the intracranial cavities to the orbit or through the bone itself, can result in restricted motility, often producing double vision, proptosis (ie, prominence of the globe), and problems with anterior segment function. Thus, pathology affecting the sellar and parasellar region frequently results in multiple ophthalmic symptoms and signs.¹⁶

The autonomic nervous system has both afferent and efferent system effects. Sympathetic and parasympathetic innervation to the pupil controls the amount of light reaching the retina, and the parasympathetic innervation to the ciliary body is responsible for accommodation (ie, the ability to see close up). Sympathetic innervation to Müller’s muscle helps lift the lid up, and parasympathetic supply to the lacrimal gland controls tear formation and, thus, the anterior refracting surface of the eye.

History

The history of visual symptoms often provides a clue to the presence of parasellar lesions and directs decisions regarding imaging. The most common ophthalmic manifestation of pathology affecting the suprasellar region is visual loss. Compression or secondary ischemic involvement of the optic nerve, chiasm, or optic tracts often produces decreased vision or less commonly appreciated visual field defects.14,17 The most important question is whether this is in one eye or both eyes. Loss of vision restricted to one eye implies globe, retina, or optic nerve pathology. If both eyes are involved, there still may be bilateral globe, retina, or optic nerve pathology, but chiasmal or retrochiasmal lesions are also in the differential diagnosis. The next question is that of the onset. Answers should include whether the visual loss is diffuse, central, or off to one side, and whether it is constant or intermittent. If variable, one needs to inquire as to what can make it better or worse, and whether it is progressive—either acutely, stepwise, or slowly. Any other associated neurologic or systemic complaints should also be sought. Patients should always be asked about a prior history of vascular disease (hypertension, diabetes, hypercholesterolemia, angina, myocardial infarct, irregular heart beat, cardiac valvular disease, or a documented stroke); inflammatory disease (demyelinating disease, infections including zoster, autoimmune conditions); cancer; or migraine. The patient’s occupation may give a clue to exposure to toxins and agents that can affect pupil size or motility, as may a travel history. It is helpful if the patient has had prior imaging studies. History often supplies clues to “where” the pathology is, which in turn alters the differential diagnosis.

As with all complaints, rule No. 1 is essential: “Get the old records.” Often, patients with complaints of visual loss will be found to have previous compromise of the visual pathways, manifested by records documenting decreased vision. Attention should be directed to identifying any source of prior ophthalmic evaluation, including the records of previous ophthalmologists and optometrists, or even the results of visual screening, such as for the Department of Motor Vehicles or military. Previous refractive correction needs to be identified, including the potential problems of nearsightedness, farsightedness, and astigmatism. If the patient wears glasses or contact lenses, these should be available and all testing done with them in place.

Bitemporal visual field defects are often unnoticed,¹⁸ and homonymous defects are often identified incorrectly as loss of vision in the ipsilateral eye. Patients may describe objects “disappearing” off to one side while they are reading. It is important to identify which parts of words seem to be disappearing as a clue to a visual field defect.

It would be unusual for parasellar pathology to present with positive visual phenomena. Positive visual phenomena, often described as zigzag lines, lights, colors, a kaleidoscope, cracked glass, or broken images, are most commonly seen with migraine. They can uncommonly be seen with cortical pathology. Rare types of formed visual hallucinations usually occur with occipital involvement, but deafferentation anywhere along the visual pathways, including the optic nerve, chiasm, and tract, may result in release phenomena as known as the Charles Bonnet syndrome.

Distortion of vision (seeing lines as bent, warped, broken, or missing, or seeing objects as too large or too small) may represent cortical pathology but is usually due to pathology affecting the retina, more specifically the macula. This can be seen with parasellar lesions that extend to involve the orbit but would be uncommon.

Additional uncommon manifestations of pathology affecting the afferent system are visual obscurations.¹⁹ These are brief, usually bilateral loss of vision, often associated with change in position. This is typical in patients with disc edema, and it may be seen with parasellar lesions that cause increased intracranial pressure. Transient visual loss associated with exercise may represent long-standing inflammation involving the optic nerves (Uhthoff phenomena²⁰). Monocular loss of vision lasting minutes may also occur with thromboembolic phenomena (amaurosis fugax, usually related to carotid disease), or dimming or darkening of vision with ocular hypoperfusion (ocular ischemic syndrome or arteritis, particularly in the elderly). Less common symptoms include darkening of vision associated with exposure to bright lights. This can sometimes be seen in patients with carotid compromise, potentially with parasellar lesions. Less commonly, transient loss of vision may be due to ocular disease (angle closure, hyphema, dry eye) and very rarely to orbital disease (gaze-evoked amaurosis secondary to an orbital tumor).

The second most common ophthalmic complaint associated with parasellar pathology is double vision.²¹ This should first be characterized as monocular or binocular, with the examiner specifically questioning whether it disappears when either eye is covered. Failure to resolve when either eye is covered indicates a monocular problem. Although this may occur as a cortical phenomenon (palinopsia), it usually represents ghost images secondary to high astigmatism due to corneal warping, surface pathology, or cataract.

Double vision that resolves by covering either eye is usually due to ocular malalignment. Attention should be directed to whether or not the double vision increases with gaze in one particular direction, specifically looking to the right or to the left, and in the four corners (up right, down right, down left, and up left). Although the natural presumption in the case of incomitant deviations (deviations that change with direction of gaze) is that they are due to a cranial nerve palsy,^22–25 it is important to recognize that alternative causes of paretic malalignment include neuromuscular transmission deficits (myasthenia gravis), and internuclear connection problems (brainstem) causing a skew deviation or internuclear ophthalmoplegia. Supranuclear palsies due to cortical or corticobulbar pathway pathology may limit motility but usually do not produce malalignment or diplopia. Limitations secondary to supranuclear processes may be overcome with infranuclear stimulation (vestibular stimulation or irrigation of the ear [calorics]).

Anatomy

The fovea, which is the most sensitive portion of the retina, has the highest spatial resolution based on its relatively high (1:1 or 1:2) ganglion-to-receptor cell ratio, (in the peripheral retina, the ratio may be as low as 1:1000). In addition, the fovea, or the center of the macula, is devoid of rods and has the highest concentration of cones, responsible for color vision. Thus, color abnormalities are a common concomitant of the dysfunction of the relatively small macular fibers, which can be compromised with compressive lesions.26 Color vision may be affected relatively early in patients with mild compression of the optic nerve. Involvement of the small fibers, which are particularly sensitive to compression, may also result in relative central scotomas. The optic nerve is approximately 1.5 mm in diameter as it exits the globe, extends less than a millimeter through the sclera, then becomes myelinated, increasing in size to approximately 3 mm. It is surrounded by the optic nerve sheath and the trabecular arachnoid, which allows cerebrospinal fluid (CSF) up to the back of the eye. This access of CSF to the back of the globe is responsible for the potential development of disc edema secondary to increased intracranial pressure.

There is redundancy in the optic nerve within the orbit, which permits the eye to move, but can be restricted if substantial proptosis ensues owing to invasion of the orbit. The central retinal artery and vein run within the optic nerve in the 8 to 10 mm just behind the globe, but outside the optic nerve posterior to this region, where the optic nerve is supplied by small branches from the optic nerve sheath. Extension of a meningioma along the optic nerve sheath can compromise the vascular supply to the optic nerve posteriorly. It also can compromise the venous outflow, resulting in the development of collaterals to the choroid circulation (optociliary shunt vessels)²⁷ (Fig. 5.1).

The optic canal measures 6 to 8 mm in length and extends superiorly and medially; it is bordered temporally by the optic strut, which separates it from the superior orbital fissure, and nasally by the sphenoid sinus. In approximately 8% of cases, there is bone dehiscence, so that the optic nerve actually may have no bony protection from pathology (or surgical exploration) within the sphenoid sinus. The exit of the optic canal takes place under a fold of dura, the falciform ligament. Pathology that elevates the optic nerve can thus compress the superior portion of the nerve, resulting in an inferior visual field defect. The intracranial portion of the optic nerve (uncovered by any dural sheath) is usually approximately 10 mm. The chiasm is variably placed, so that in the case of a preplaced chiasm, there may be a much shorter distance from the exit of the canal to the beginning of the chiasm. Similarly, in a relatively postplaced chiasm, the intracranial portion of the optic nerve may be longer, such that the chiasm actually rests posterior to as well as superior to the sella. This variability is responsible for the spectrum of clinical manifestations seen in suprasellar tumor involvement. In the setting of a relatively postplaced chiasm, tumors or other mass lesions of the parasellar region often involve the optic nerve, producing central scotomas and arcuate visual field defects (Fig. 5.2). In the setting of a preplaced chiasm, tumors that arise from the sella can compress the optic tract, producing homonymous visual field defects.¹⁷

Fig. 5.1   Photo of the right fundus (A) of a 54-year-old woman who presented with a 7-year history of progressively decreased vision in the right eye. When evaluated, she had no light perception in the right eye and 9 mm of proptosis (B). MRI reveals evidence of a skull base meningioma involving the tuberculum (C) and invading the orbit (D), producing the optociliary shunt vessels indicated in the fundus (A). Comment: Optociliary shunt vessels are pathophysiologically associated with compromise of the central retinal venous outflow. They are most commonly seen with central retinal vein occlusion but when associated with optic atrophy may be due to an optic nerve sheath meningioma or a parasellar meningioma invading the orbit.

The optic nerves meet and create the chiasm, which lies variably above the level of the sella. Because more of the pupillary fibers in the anterior visual pathways cross than do not cross, pathology affecting the optic tract may produce a contralateral afferent pupillary defect28 (Fig. 5.3). Damage to the tract may have a second distinguishing characteristic (not seen in cortical or optic radiation pathology) because retrograde degeneration will result in band (or bowtie) atrophy in the contralateral optic nerve head. It should be noted that this takes weeks to months to occur and will not be seen in the setting of an acute tract lesion, whereas the contralateral afferent pupillary defect develops immediately.

The chiasm is usually inclined at about a 45-degree angle, so that pathology arising from the sella most frequently affects the anterior and inferior aspects of the chiasm, first producing the characteristic superior bitemporal visual field defects seen in most patients with suprasellar pathology^29,30 (Fig. 5.4). The macular fibers tend to cross more posteriorly within the chiasm, and involvement of the posterior chiasm or the anterior third ventricle can result in relatively bitemporal scotomatous defects or bitemporal inferior field defects (Fig. 5.5).

Recent studies have suggested that the looping of the crossing fibers into the contralateral optic nerve, described in earlier anatomy texts, is an artifact of the patients who were in the original studies (following enucleation or loss of an eye).³¹ Even though the so-called Wilbrand knee³² is probably an artifact, pathology that affects the optic nerve just anterior to the chiasm often produces a central scotoma with a relative temporal defect in the opposite eye. This, therefore, remains a useful localizing sign. Rarely, a lesion may compress the optic nerve without touching the anterior chiasm. This can produce a unilateral temporal field defect, referred to as the junctional syndrome of Traquair.³³ Involvement of the posterior aspect of the chiasm is potentially seen with craniopharyngiomas or other pathology affecting the pituitary stalk, including sarcoid, histiocytosis, and germinomas. Even with posterior chiasmal compression, however, the majority of lesions are pituitary tumors because these are simply much more common.

Efferent System

The efferent visual pathways originate within the horizontal and vertical gaze centers, located within the pons and midbrain, respectively. The horizontal gaze center itself is actually within the abducens nerve nucleus, although the burst cells, which are within the paramedian pontine reticular formation, generate horizontal saccades. Pathologic involvement of the horizontal gaze center results in absence of gaze to that side. The opposite eye can still adduct owing to convergent triggering of the medial rectus in the area of the midbrain.

The vertical gaze centers are located within the dorsal rostral midbrain tegmentum. A set of three nuclei (the rostral interstitial nucleus of the medial longitudinal fasciculus [MLF], the interstitial nucleus of Cajal, and the nucleus of Darkschewitsch) are responsible for coordinating vertical gaze movements. Compression of the dorsal portion of the midbrain,³⁴ such as is seen with extension of lesions of the pineal gland, can result in a classic dorsal midbrain syndrome, with absent up gaze, retraction convergence nystagmus, Collier’s sign of lid retraction, and light near dissociation due to involvement of the pupillary crossing fibers in the posterior commissure.³⁵ Seesaw nystagmus is a rare finding in patients with parasellar lesions that extend to compress the midbrain.³⁶ In this, one eye will elevate and intort, while the other eye depresses and extorts. This pattern then reverses.

Signals from the horizontal and vertical gaze centers travel to the extraocular muscles via the third (oculomotor), fourth (trochlear), and sixth (abducens) cranial nerves. The sixth nerve exits the pontine brainstem to run in the subarachnoid space up the clivus. It pierces the dura and enters Dorello’s canal underneath the petroclinoid ligament (in conjunction with the inferior petrosal sinus), entering into the body of the cavernous sinus, where it crosses next to the carotid artery. The sympathetic fibers in the wall of the carotid artery leave the carotid within the cavernous sinus in conjunction with the sixth nerve to run more anteriorly before entering the superior orbital fissure along with branches of the first division of the fifth cranial nerve (nasociliary branch).³⁷ The sixth nerve enters through the superior orbital fissure within the annulus of Zinn to innervate the lateral rectus muscle approximately one-third of the way anteriorly along its medial surface.

The fourth, or trochlear, nerve nucleus is located just caudal to the third nerve nuclear complex within the tegmentum of the midbrain. Its branches run dorsally to cross in the superior medullary velum. It is the only cranial nerve that exits the brain dorsally and has the longest unprotected course in the subarachnoid space. It runs around the midbrain and travels along the edge of the tentorium anteriorly to enter the lateral wall of the cavernous sinus between the third nerve above it and the first division of the fifth nerve below it. The fourth nerve can be easily injured when the tentorium is opened (Fig. 5.6). The trochlear nerve is the only motor nerve that runs outside the annulus of Zinn, crossing over the optic nerve to innervate the superior oblique muscle approximately one-third along its course. Surgery to reach the optic nerve through the superior orbit can damage the trochlear nerve as it crosses in the orbital apex.

Fig. 5.2   The fields (A,B) of a 65-year-old woman who presented with a 1-year history of progressive visual loss in the right eye. Visual acuity was 2/200 OD and 20/30 OS with a >1.8 log unit right afferent papillary defect. The right field (B) demonstrates a central scotoma, and the left field (A) demonstrates an inferior arcuate defect. Her funduscopic examination (C,D) revealed evidence of drusen of the optic nerve heads bilaterally with relative optic atrophy OD > OS. The view on the right (C) was much better than the view on the left (D) because she had had her cataract on the right side removed. The arcuate changes on the left eye were compatible with the buried drusen, and the difference between the total deviation plot and the pattern deviation plot was presumably related to her cataract.

Fig. 5.2   (Continued) The central scotoma in the right eye, however, could not be explained by the optic nerve head drusen, and an angiogram revealed evidence of bilateral ophthalmic segment internal carotid artery aneurysms with right optic nerve compression (E). Evidence of bilateral optic neuropathies were confirmed on the optical coherence tomogram (OCT), which shows thinning of nerve fiber layer in both eyes (F).

Fig. 5.2   (Continued) B-scan reveals hyperrefractile bodies in the optic nerve head (G,H), demonstrating that this is optic nerve head drusen, not papilledema. She underwent stenting and coil embolization of both carotid aneurysms (I) with stabilization of her visual function. Comment: Although central scotomas are most commonly associated with macular disease, certain optic neuropathies often cause central loss of vision. Rare causes include nutritional, toxic, and hereditary (Leber) optic neuropathies. Inflammatory and compressive lesions are more common causes of visual loss. In this case, a paraclinoid aneurysm compressed the right optic nerve, producing visual loss and a central scotoma. B-scan of the optic nerve head can help distinguish papilledema (disc elevation due to increased intracranial pressure) from optic nerve head drusen.

Fig. 5.3   This 50-year-old patient was referred in September of 2008. Seventeen months earlier, she had developed a “funny smell” and was seen by her local doctor, who ordered MRI. This revealed evidence of a right temporal lobe lesion, and she underwent a craniotomy in May of 2007 (16 months before her evaluation) with subtotal resection of a high-grade glioma. Three days before her referral, she had noticed increasing problems seeing to the side. Visual fields reveal a fairly dense left homonymous hemianopsia (A,B). Visual acuity was preserved with 20/30 vision at distance and 4-point vision at near. She did, however, have a 0.9 log unit left afferent pupillary defect, indicating involvement of the right optic tract, which produced the left homonymous hemianopsia. Her discs at that time looked normal, and an optical coherence tomogram (OCT) of her nerve fiber layer also looked entirely normal (C).

Fig. 5.3   (Continued) This 50-year-old patient was referred in September of 2008. Seventeen months earlier, she had developed a “funny smell” and was seen by her local doctor, who ordered MRI. This revealed evidence of a right temporal lobe lesion, and she underwent a craniotomy in May of 2007 (16 months before her evaluation) with subtotal resection of a high-grade glioma. Three days before her referral, she had noticed increasing problems seeing to the side. Repeat scan at this time revealed a lesion extending from the temporal lobe to involve the basal ganglia as well as the right optic tract (D–G). Three months later, she returned with visual acuity down to 1/200 in the right eye and 20/30 in the left. She now had a dense left homonymous hemianopsia. Her afferent pupillary defect had increased to 1.8 log unit.

Fig. 5.3   (Continued) This 50-year-old patient was referred in September of 2008. Seventeen months earlier, she had developed a “funny smell” and was seen by her local doctor, who ordered MRI. This revealed evidence of a right temporal lobe lesion, and she underwent a craniotomy in May of 2007 (16 months before her evaluation) with subtotal resection of a high-grade glioma. Three days before her referral, she had noticed increasing problems seeing to the side. Three months later, she returned with visual acuity down to 1/200 in the right eye and 20/30 in the left. She now had a dense left homonymous hemianopsia. Her afferent pupillary defect had increased to 1.8 log unit. Although her optic discs did demonstrate some subtle optic atrophy, OD (H) greater than OS (I), the progressive damage to the anterior visual pathways could be better seen in her OCT, which showed severe thinning of the nerve fiber layer on the right side and moderate thinning of the nerve fiber layer on the left (J). Comment: Optic tract involvement may be suspected when there is an afferent pupillary defect on the same side as the visual defect. OCT, by giving us an in vivo biopsy, is a more quantitative way of assessing damage to the anterior afferent visual pathways. Although it is likely that when we first saw her she already had ongoing damage to the optic tract, there is a delay in the development of thinning of the nerve fiber layer and subsequent optic atrophy. The quantitation of her afferent pupillary defect also demonstrated progression, indicating involvement not only of the right optic tract but also subsequently of the right optic nerve in this patient with an aggressive glioblastoma.

Fig. 5.4   This 40-year-old woman presented with a 3-week history of headaches and 2 weeks of blurred vision. Visual acuity was found to be 20/40 and 20/200 with near vision of 4 point and 26 point. Her visual fields revealed asymmetric bitemporal visual field defect (A,B). Interestingly, her discs really did not look that abnormal (C,D), and her optical coherence tomogram (OCT) showed normal nerve fiber layer thickness (E).

Fig. 5.4   (Continued) This 40-year-old woman presented with a 3-week history of headaches and 2 weeks of blurred vision. Visual acuity was found to be 20/40 and 20/200 with near vision of 4 points and 26 points. Interestingly, her discs really did not look that abnormal (C,D), and her optical coherence tomogram (OCT) showed normal nerve fiber layer thickness (E). Her MRI revealed a suprasellar mass lesion compressing the chiasm (F–H).

Fig. 5.4   (Continued) This 40-year-old woman presented with a 3-week history of headaches and 2 weeks of blurred vision. Visual acuity was found to be 20/40 and 20/200 with near vision of 4 points and 26 points. Her prolactin was elevated at 739 ng/mL. She was started on cabergoline (Dostinex) 0.5-mg tablets twice a week, and 6 weeks later she had dramatic improvement in automated static perimetry (I,J). Comment: Superior bitemporal defects are the most common chiasmal syndrome due to compression of the anterior inferior chiasm by a lesion arising from the sella. Elevated prolactin indicated a prolactinoma, which responded well to medical treatment with cabergoline. Quantitative improvement in perimetry is common with medical or surgical decompression of the chiasm. The normal OCT indicated that the compression was probably not long-standing and might be a good prognostic indicator for visual recovery.

Fig. 5.5   This 53-year-old patient was referred to the neuro-ophthalmology office because of “another tumor.” Her visual fields demonstrated an inferior bitemporal visual field defect (A,B), and her optic discs indicated optic atrophy (C,D).

Fig. 5.5   (Continued) This 53-year-old patient was referred to the neuro-ophthalmology office because of “another tumor.” Her optical coherence tomogram (OCT) confirmed the presence of bilateral optic atrophy with nerve fiber bundle dropout, more on the left than the right (E). Her past medical history was remarkable for galactorrhea in 1992. She was found to have an elevated prolactin level and in June of 1995 had undergone transsphenoidal resection of a cystic nonsecretory pituitary tumor. Review of her MRI demonstrated a cystic lesion arising from the sella and compressing the posterior aspect of the chiasm (F–H).

Fig. 5.5   (Continued) This 53-year-old patient was referred to the neuro-ophthalmology office because of “another tumor.” She returned 6 months later stating that her vision had not changed, but automated static perimetry now demonstrated denser bitemporal visual field defects (I,J), though her discs showed no change (K,L).

Fig. 5.5   (Continued) This 53-year-old patient was referred to the neuro-ophthalmology office because of “another tumor.” OCT demonstrated further thinning of her nerve fiber layer on the right side (M). She underwent decompression of what pathologically proved to be a Rathke cleft cyst. Within 6 months, her visual fields had improved, although still with a residual bitemporal defect (N,O).

Fig. 5.6   This 46-year-old patient was referred for double vision. Her nine cardinal positions indicate a left hypertropia increasing with right gaze and with left head tilt (A). She measured 16 diopters of left hypertropia in primary position. The Hess screen confirms a left hypertropia deviation increasing on down right gaze (B). She had previously presented with a history of left facial numbness and had undergone resection of a left tentorial meningioma that caused her nerve IV palsy. Subsequently she underwent a right inferior rectus recession, which resolved her double vision as seen in her Hess screen (C). Comment: The fourth nerve is easy to injure when surgery involves the tentorial edge. Eye muscle surgery may correct the malalignment if it does not clear spontaneously.

The inner surface of the globe is lined by a photosensitive layer, the retinal receptors, consisting of rods and cones. The rods line the entire retina except for the fovea. The cones are also located throughout the retina but are concentrated in the fovea. The retinal receptors send signals via the bipolar cells to the ganglion cells located in the most inner portion of the retina. The axons of the ganglion cells make up the nerve fiber layer, which then forms the optic nerve.

Evaluation

A basic understanding of the neuro-ophthalmic examination includes qualitative and quantitative assessment of the afferent and efferent systems. Multiple texts and chapters have addressed the neuro-ophthalmic evaluation of the afferent system.15,33,38–44 Ophthalmic evaluations, like all examinations, can be divided into those that are qualitative, potentially localizing in nature, and those that are quantitative, providing for an assessment of the natural history of disease as well as the effects of intervention. Qualitative assessment is often adequate to confirm the presence of a lesion and to direct additional work-up. Quantitative assessment is required, however, to determine whether or not lesions are changing over time, and whether therapy has been effective.

Although qualitative acuity measurements may be listed as “normal” or “reduced,” in almost all circumstances quantitative measurement of afferent visual function should be obtained. It is important to recognize that central vision as measured by Snellen or near acuity represents only macular function, and it does not assess visual perception outside the point of fixation. Macular function is traditionally recorded as the smallest Snellen optotype that can be seen, usually at the fixed distance of 20 ft. The top of the fraction recorded (eg, 20/40) indicates the testing distance and the bottom smallest optotype that can be seen. Thus, in this case, at 20 ft the patient cannot see anything smaller than the 40 optotype. The optotype is defined by the size of the letter required to subtend 5 minutes of arc at the named distance. Small improvements in distance acuity testing were introduced by Bailey and Lovie in 1976, and a modification of the chart (also called the ETDRS [Early Treatment Diabetic Retinopathy Study] chart), is often used in multicenter trials.45 All visual function testing should be obtained with the patient’s correction (glasses or contact lenses) in place. Often, acuity seems to be lost simply because the patients are not wearing their glasses. A rapid screen for the presence of refractive abnormalities, as well as corneal or surface anomalies, can be obtained with the use of a pinhole. Improvement in central visual function when the patient looks through a pinhole usually indicates that at least a component of the decreased vision is related to uncorrected refractive error, or potentially to early corneal or lens pathology.

In addition to best corrected distance acuity, near vision should be checked routinely (Fig. 5.7). Although this may be recorded as “equivalent,” as a general rule, it should be recorded in the point system, again with the appropriate refraction for near, and with a notation of the distance at which the patient is holding the reading card. The Jaeger system, although used by ophthalmologists, does not have the universal applicability (the point system is used in all type, including computer printouts) and therefore is less useful. Lack of equivalence between distance and near measurement is another clue to the possibility of an uncorrected refractive error, but it also may occur in patients with various types of cataract formation.

An additional essential part of evaluation of the afferent system is testing extrafoveal function (visual fields).^33,41 This can be done qualitatively by confrontation testing (Fig. 5.8), semiqualitatively on tangent screen testing, and quantitatively by Goldmann or automated static perimetry.⁴⁶ At a minimum, all patients should be assessed for the potential presence of visual field defects that respect the vertical midline, indicating chiasmal or retrochiasmal pathology, or the nasal horizontal midline, indicating optic nerve pathology. In addition, as compressive lesions may affect the central portion of the visual field, patients should be tested for relative central visual field defects. These are common with optic nerve compression. Visual fields (like other afferent system tests) should be recorded as if you are the patient looking out. Thus, the right visual field is to the right side and the left is to the left, with the temporal fields peripherally and the nasal fields centrally.

Fig. 5.7   Near card. Instructions call for this to be held at 14 in (35.6 cm). It is more important that the patient hold the card at the clearest distance and that distance be measured and recorded. Vision should be recorded in the point system. The equivalent subtended angle at distance is also given.

Visual field defects are particularly useful in localizing pathology, even without quantitative assessment. Bitemporal visual field defects, originally described clinically by McKenzie in 1835, clearly localize pathology to the area of the chiasm (Figs. 5.4 and 5.5). Homonymous visual field defects, in which there is a field defect to the same side in both eyes, indicates pathology affecting the post-chiasmal visual pathways (Fig. 5.3). Involvement of the optic nerves may produce either a central scotoma (Fig. 5.2) or variations of arcuate visual field defects, found on qualitative assessment by a relative step across the nasal horizontal midline. Arcuate defects are better evaluated in a more quantitative fashion either by Goldmann kinetic perimetry or automated static perimetry. In the interpretation of visual fields, the pattern deviation plot with statistical analysis is most important in terms of recognizing and appreciating the localizing value of visual field defects. Arcuate defects indicate pathology affecting the optic nerve (less likely the retina), whereas respect for the vertical midline indicates involvement at or behind the chiasm. Central scotomas not due to macular pathology are classically seen with toxic, metabolic, or hereditary pathology, but are not uncommon with compressive or inflammatory lesions.

Fig. 5.8   Confrontation testing should be done by presenting one, two, or five fingers in each of the four quadrants, with each eye tested separately.

Evaluation of the afferent system also involves two additional studies: assessment of pupillary response and assessment of the retina and optic disc. Teleologically, the pupil is responsible for regulating the amount of light coming into the visual system.47 When there is excess light, the pupils become smaller, and when it is relatively dark, the pupils dilate. This is under control of the sphincter muscle, innervated through the third nerve, and the dilator muscles, innervated by the sympathetics traveling with the carotid artery through the superior orbital fissure. Pupils should be examined for regularity and symmetry. Pupil size may be measured with a pupil gauge. Asymmetry is not rare, essential anisocoria, but the difference should be the same in light and dark.⁴⁸

The presence of asymmetric optic nerve pathology produces an afferent pupillary defect; moving a bright light from one side to the other results in dilation of both pupils when the light is moved to the side where the optic nerve is involved while the patient fixes a distant accommodative target.⁴⁹ The presence of an afferent pupillary defect may be further quantitated by the placement of neutral-density filters in front of the better-functioning eye until the response is balanced⁵⁰ (Fig. 5.9). Although an afferent pupillary defect cannot be detected in a patient with one eye, it is possible to detect an afferent pupillary defect even when there is only one working pupil. Statements about “reverse Marcus Gunn” pupil should be avoided. No matter which pupil is being observed, the relative afferent pupillary defect indicates the side on which less light is getting into the system. The presence of an afferent pupillary defect parallels asymmetric visual fields more than central acuity and optic nerve appearance.

The eye gives us a unique ability to see in vivo into the functioning of the central nervous system. Funduscopic evaluation permits us to look at the beginning of the optic nerve, which is really the most anterior portion of the white matter tract of the brain connecting the photoreceptors via the ganglion cells to the geniculate and then the cortex. The presence of increased intracranial pressure, potentially seen in patients with parasellar lesions, can produce disc edema as it results in constipation of axonal transport (Fig. 5.10). Persistent disc edema due to increased intracranial pressure will eventually produce optic atrophy associated with deteriorating afferent visual function. This may be documented with photographs of the posterior pole and can be qualitatively assessed based on relative disc pallor and more recently quantitatively assessed with OCT (optical coherence tomography; Fig. 5.5). Papilledema is uncommonly seen with pituitary tumors unless they become large enough to obstruct the foramen of Monro. Other tumors arising in the parasellar region, however, more frequently present with increased intracranial pressures, especially meningiomas arising from the olfactory groove, from the tuberculum, or even from the anterior clinoid and medial sphenoid wing. These may present with bilateral disc edema due to increased intracranial pressure or unilateral disc edema and contralateral optic atrophy (Foster Kennedy syndrome) due to compression of one optic nerve.⁵¹

It should be noted that since the advent of imaging studies, the incidence of disc edema with all intracranial tumors has markedly decreased.¹⁴ This would be particularly true in patients with parasellar lesions, as it would be unusual for patients to be asymptomatic long enough for these lesions to reach the size that leads to papilledema.

Fig. 5.9   In the presence of an afferent pupillary defect, neutral density filters may be placed in front of the better-functioning eye to quantitate the amount of asymmetry between the two eyes. It is important to use a bright light and spend equal time in the two eyes.

Fig. 5.10   This 39-year-old patient presented in August 2006 with a 1-month history of pounding headaches. Visual acuity was 20/20 bilaterally, but his visual fields demonstrated enlargement of the blind spot bilaterally, worse on the left (A) than the right (B), and bilateral disc edema (C,D).

Fig. 5.10   (Continued) This 39-year-old patient presented in August 2006 with a 1-month history of pounding headaches. Visual acuity was 20/20 bilaterally, but his visual fields demonstrated enlargement of the blind spot bilaterally, worse on the left (A) than the right (B), and bilateral disc edema (C,D). Optical coherence tomography (OCT) confirmed the presence of marked thickening of the nerve fiber layer bilaterally, worse on the right than the left (E).

Fig. 5.10   (Continued) This 39-year-old patient presented in August 2006 with a 1-month history of pounding headaches. MRI revealed evidence of significant hydrocephalus, with a small colloid cyst blocking the foramen of Monro (F–I).

Fig. 5.10   (Continued) This 39-year-old patient presented in August 2006 with a 1-month history of pounding headaches. Following excision of the colloid cyst, the discs are seen to return to normal (J,K), and the OCT shows marked thinning with return to normal (L). Comment: Obstruction of ventricular flow in this case resulted in secondary increased intracranial pressure with bilateral disc edema and bilateral cecal scotomas. With restoration of the normal CSF flow, pressure was reduced, the disc edema resolved, and the thickening of the nerve fiber layer reversed (as seen on OCT).

The recent development of OCT has opened a new door to the more quantitative assessment of the optic nerve, disc, and nerve fiber layer. This can be seen to be thickened in patients with disc edema of any etiology (Fig. 5.10) and, more importantly, can quantitate the presence of loss of nerve fiber layer due to pathology that affects the optic nerve (paralleling optic atrophy; Fig. 5.5). It should be noted that there is a delay in the thinning of the nerve fiber layer for weeks, if not months, between the acute onset of optic nerve pathology and thinning seen on OCT. It is also important to note that the OCT will not thin to zero because there are support structures within the retina that will keep nerve fiber layer thickness measurements at least in the upper 30s or lower 40s range. Asymmetry between the two sides may be a useful sign of previous damage to one optic nerve. A finding of nerve fiber layer thinning may also indicate that a lesion is much more long-standing than otherwise appreciated (Fig. 5.3). OCT may also be prognostic in terms of visual recovery following surgical or medical decompression (Fig. 5.4). Just as the older literature suggested that the best prognosis was in patients with relatively brief visual loss and the absence of optic atrophy on funduscopic evaluation, the lack of OCT thinning may also be taken as a relatively good prognostic sign for potential recovery. Conversely, the presence of significant thinning of nerve fiber layer may indicate a worsened prognosis for recovery following decompression. It should be emphasized, however, that even with significant thinning, there may be substantial improvement in optic nerve function, particularly as measured by central acuity, but even by visual fields.

It is important to note that not all decreased vision is due to optic nerve or chiasmal pathology. Abnormalities in refraction and abnormalities of the cornea, lens, vitreous, or retina can also produce decreased vision. This will often require more detailed work-up. One of the tests that may be particularly suggestive of an alternative explanation for visual loss would be the absence of an afferent pupillary defect. Although an afferent may not be present if both optic nerves are involved, the presence of unilateral decreased vision but no afferent pupillary defect strongly suggests either an anterior segment or a retina problem. In photo-stress test a light is shined in the eye for 10 seconds, then the patient is timed until he or she can read down to one line worse than best previoiusly recorded vision. This may be a subtle way of detecting a relative macular problem as differentiated from an optic nerve problem.⁵² Patients who have macular pathology will have a delay in their recovery, whereas patients with optic nerve problems will not.

The view of the back of the eye may also be very helpful. If there is an anterior segment problem, the observer often cannot see in with a direct ophthalmoscope (Fig. 5.11), and therefore, it is not surprising the patient cannot see out. Similarly, clear macular pathology may explain the patient’s visual limitation. The appearance of the macula, unfortunately, does not always indicate its function. Additional functional tests, such as multifocal electroretinography (ERG) and autofluorescence, and anatomic tests, such OCT of the macula, may be necessary.

Fig. 5.11   Direct ophthalmoscope. Although a more detailed view (and in stereo) may be obtained with slit-lamp biomicroscopy or with indirect ophthalmoscopy, the direct ophthalmoscope gives a good idea of any media (cornea, lens, anterior segment) problems that may be interfering with vision. If you can see in, the patient should be able to see out.

Extensive literature addresses the importance of ocular motility to visual function.21,53,54 Because we are foveate animals, to maximize our visual potential, we need to bring the eyes into alignment with the object of interest. To do that, we have developed the efferent visual system, which allows the movement of each eye. In addition, because we have overlapping visual fields, both eyes must be in alignment simultaneously. Acuity is adversely affected by movement of the eye relative to the visual environment. Thus, it is critical that the eyes be kept stable. This includes stability when the head moves and when the object of interest moves. Stability can be best judged by observing the fundus with a direct ophthalmoscope.⁵⁵ Any tendency for the eye to drift will be picked up as a movement of the observed optic disc. This can be done in primary and eccentric gaze. Gross instability may be directly observed, magnified with a Fenzel viewing system, or recorded with an eye-tracking system (electro-oculogram [EOG], infrared, coil).⁵⁶

Movement of the two eyes together is referred to as version. These may be movements left (levoversion), right (dextroversion), up (sursumversion), or down (deorsum-version). Vergence refers to movements of the eyes in opposite directions. Convergence is necessary to look at a near target, bringing the axes closer together, and divergence is required for looking at a distance target. Abnormalities of convergence and divergence can occur with midbrain lesions and can uncommonly be seen with parasellar lesions that enlarge to affect or involve the midbrain. Abnormal versions can lead to ocular malalignment. This, as mentioned, usually results in diplopia. Subtle abnormalities in versions can be picked up by dissociative tests such as the red glass test or, better yet, the use of a Maddox rod.57 A white light is viewed by one eye while a Maddox rod placed over the opposite eye produces the sensation of seeing a line perpendicular to the cylinders of the Maddox rod. To assess horizontal alignment, the Maddox rod is placed so that the cylinders are aligned horizontally, thus producing the sensation of seeing a line running vertically (Fig. 5.12A). If the light is not seen as on the line, then there is relative horizontal malalignment of the eyes. As the patient will see the light in the opposite direction to which the eye is deviated, if the patient reports seeing the light as crossed over the line, it means that the patient has a relative exodeviation, or deviation out. Similarly, if the patient reports the light on the same side as the eye viewing, the patient has the eyes relatively crossed in, or an esodeviation. If the Maddox rod is aligned vertically, the patient will see a horizontal line (Fig. 5.12B). If the light is above or below the line, there is a vertical deviation. A tendency to deviate (phoria), as picked up by a Maddox rod or red glass, is common in a large percentage of the population. Most people, however, maintain alignment by the use of fusional amplitudes, which can make up for a tendency of the eyes to deviate. A breakdown of the fusional amplitudes results in a manifest deviation (tropia). Torsional abnormalities (often seen when the third or fourth nerve is involved) can be measured with double Maddox rods. Occasionally, patients are unable to perform Maddox rod or other subjective tests. Alignment may be assessed by cross-cover testing and prism measurements or, in nonresponsive patients, by judging the position of the light reflex on the cornea (Hirshberg’s test). A more quantitative test not requiring patient response is Krimsky’s test, in which the light reflex is simultaneously centered on the cornea with the use of prisms, thus placing a number on deviation.58

Fig. 5.12   Maddox rod. Although a red glass or cross-cover testing may also be used to check for alignment, the Maddox rod is a very quick means of assessing for any tendency to deviate (phoria) both horizontally (A) and vertically (B). This is the quickest way to check for comitance and identify the field of maximal deviation.

Although the red glass test and Maddox rod are usually considered qualitative (assessing the presence of deviation but not quantitating it), it is possible to use them to quantitate deviation by adding a prism to balance the deviation. Quantitative assessment of ocular deviation may also be obtained by cross-cover testing in primary position, measuring both horizontal and vertical deviation with prisms and also the deviation in the other eight cardinal positions of gaze, including up, down, left, right, up right, down right, up left, and down left. Prism measurements will depend on which eye is under the prism. In incomitant deviations, when the patient fixates with the normal eye and the prisms are placed over the abnormal eye, one measures the “primary” deviation. If the prisms are then switched to the normal eye, the deviation measured when the abnormal eye is fixating is called the secondary deviation. The secondary deviation is always greater than the primary. In the setting of a comitant deviation (the same in all directions), the primary and secondary deviations are equal. In addition to the quantitative use of orthoptic or cross-cover testing with prisms, the use of a Lancaster red-green test59,60 or a Hess screen⁶¹ gives a semiquantitative assessment of ocular motility. This is particularly useful in following patients with ocular deviation (Fig. 5.13).

An additional quantitative assessment of ocular deviation can be obtained by using a Goldmann bowl and plotting the area of binocular singularity. Thus, a patient with an abduction deficit, perhaps due to a sixth nerve palsy, may be seen to have double vision when looking in the direction of the sixth nerve dysfunction but single vision when looking away. By plotting the binocular single vision fields, patients can be followed to determine whether or not sixth nerve function is improving or worsening. It should be noted that finding a deviation, either qualitatively and quantitatively, does not tell you whether the deviation is due to a paretic problem (eg, a cranial nerve palsy, a neuromuscular transmission deficit, or an internuclear problem) or due to restrictive phenomena secondary to local orbital invasion. Restrictive syndromes are traditionally diagnosed by forced ductions but may also be recognized with the use of a suction cup⁶² or the elevation of intraocular pressure in eccentric gaze.⁶³ Rarely, ocular malalignment may be due to primary overaction syndromes. Parasellar lesions that can produce overaction include ocular neuromyotonia, which often follows radiation of lesions in the parasellar region. Patients with ocular neuromyotonia can report a sensation of the eye “sticking” when they look in the direction of the affected muscle. In sixth nerve ocular neuromyotonia, when the patient looks to that side, the lateral rectus muscle will continue to fire even after the patient looks back straight, resulting in a transient exodeviation producing double vision.

Fig. 5.13   This 24-year-old presented with a 4-month history of intermittent diplopia. Visual acuity and visual fields were normal, but she had upbeat nystagmus in primary position increasing on up gaze. MRI demonstrated a dorsal midbrain intra-axial lesion with an exophytic component (A,B).

Fig. 5.13   (Continued) This 24-year-old presented with a 4-month history of intermittent diplopia. Visual acuity and visual fields were normal, but she had upbeat nystagmus in primary position increasing on up gaze. She underwent a suboccipital craniotomy and biopsy, which demonstrated a low-grade glioma. Postoperatively she had worsening of her diplopia, with an exo deviation increasing on gaze to either side (C) and a right hypertropia increasing on left gaze and with right head tilt. Hess screen confirmed the incomitant vertical deviation (D). Two months later, her double vision had significantly improved (E). Comment: Following craniotomy, this patient had evidence of bilateral internuclear ophthalmoplegia and a right fourth nerve palsy, which spontaneously improved. The Hess screen provides quantitative follow-up.

Making the diagnosis of a cranial nerve palsy depends on whether or not it fits a pattern. A sixth nerve palsy should be seen as an esodeviation increasing on ipsilateral gaze and decreasing on contralateral gaze (Fig. 5.14). The deviation should be minimal when the patient looks away from the side of the sixth nerve. A fourth nerve palsy consists of an ipsilateral hyperdeviation that increases on contralateral gaze and ipsilateral head tilt (Fig. 5.6). The deviation should be minimal when the patient looks up and to the same side as the involved superior oblique. A third nerve palsy produces the pattern of an exodeviation increasing on contralateral gaze and a variable hyperdeviation with a contralateral hyperdeviation on up gaze and an ipsilateral hyperdeviation on down gaze (Fig. 5.15). This may be variable depending on whether or not there is divisional third nerve palsy. Two additional “fellow travelers,” the eyelid position and the pupil, should be assessed. Specifically, because the third nerve innervates the levator, there is usually a concomitant ptosis, and because the third nerve also controls the sphincter muscles of the iris, the pupil on that side is often larger and does not react normally.

In the setting of a complete third nerve palsy, fourth nerve function can be determined by whether the patient has incyclotorsion while looking down. Small vessels at the limbus can be observed to see if they rotate in when the patient attempts to follow down. The finding of a concomitant fourth and third nerve palsy usually indicates cavernous sinus pathology. Multiple cranial nerve palsies may occur, particularly in the setting of cavernous sinus pathology secondary to parasellar extension.^16,64,65 However, “pieces” of a third nerve palsy, such as isolated medial rectus or isolated inferior rectus weakness, are unlikely to be related to third nerve dysfunction. Instead, they more likely indicate other causes of ocular motor problems, including myasthenia gravis, skew deviation, and restrictive pathology. The pattern of deviation is particularly easily seen on a Hess screen but also can be assessed quickly with a Maddox rod or red glass.

The acute onset of multiple cranial nerve palsies is characteristic of pituitary apoplexy.^66–68 These are often bilateral and accompanied by involvement of the afferent visual pathways, resulting in decreased vision, afferent pupillary defect, and field defects plus associated mental status changes. This event was originally felt to be an uncommon condition related to bleeding into a preexisting pituitary tumor. The advent of imaging has indicated that small bleeds into pituitary tumors are far more common than previously documented, and most patients do not have a substantial change in their symptomatology. Nonetheless, variations of pituitary apoplexy still do occur, and the sudden onset of multiple cranial nerve palsies and afferent system dysfunction should bring that to mind.

Fig. 5.14   This 78-year-old woman presented in September 2009 with double vision. Her afferent system was entirely intact, but her nine cardinal positions demonstrated an abduction deficit on the left (A).

Fig. 5.14   (Continued) This 78-year-old woman presented in September 2009 with double vision. This is confirmed on her Hess screen, which shows a limitation in left abduction (B). CTA revealed a left carotid cavernous aneurysm (C). Her pupils were also noted to be unequal, with a miotic pupil on the left side and mild ptosis (D). Following Iopidine, the smaller left pupil now is larger, indicating hypersensitivity on the left (E). Comment: This is an example of a combined left sixth nerve and Horner syndrome secondary to a carotid artery aneurysm. The pattern of deviation is easily appreciated on the Hess screen.

Fig. 5.15   This 62-year-old man presented in May of 2002 with a 3-week history of double vision. His acuity was 20/20 and 20/25 with 3-point near vision and full visual fields, but he had complete ptosis OS. Although there was no afferent pupillary defect, the pupil on the left was dilated to 5.5 mm and was nonreactive. His motility demonstrated essentially absent adduction, elevation, and depression on the left (A). His motility problem was confirmed on the Hess screen (B). MRI demonstrated a mass in the sella and left cavernous sinus (C), which proved to be metastatic adenocarcinoma. Comment: The Hess screen demonstrates the pattern of a left third nerve palsy, with the primary deviation on the left and the secondary overaction on the right.

Adnexal assessment is addressed by measuring the palpebral fissure opening, usually with a millimeter ruler (Fig. 5.16). Upper lid range gives a clue to the function of the levator muscle and Müller’s muscle (Fig. 5.17 A,B). The presence of ptosis can be quantitated by measuring the distance between the center light reflex on the cornea and the upper lid margin. This median reflex distance (MRD; Fig. 5.18) decreases in patients with ptosis, or lid droop, and increases in patients with lid retraction. The presence of pathology within the orbit may be suspected by widening of the palpebral fissure, clear evidence of the eye bulging, or more quantitative evidence of relative proptosis or exophthalmos. An additional qualitative assessment may simply be obtained by looking over the patient’s forehead for evidence of increased prominence of the globe. Hertel measurements are used to quantitatively assess the distance from the orbital rim to the corneal plane (Fig. 5.19). Although the range for normal patients has been published (varying by population), far more valuable is the symmetry expected between the two sides. More than 2 mm of difference between the two eyes usually calls for an explanation. A previous history of trauma, inflammation, or orbital tumors should be sought before it is assumed that this is related to intraorbital extension of parasellar pathology. Proptosis that varies, particularly induced by Valsalva maneuver or bending forward, usually indicates a vascular anomaly such as a venous varix. Rarely, pulsations of the eye may be seen with loss of the bony confines of the orbit. This may be related to previous surgery but can occur with congenital, neoplastic, or vascular anomalies eroding the bone. Vascular abnormalities including carotid cavernous fistulae may also cause pulsations.

One other clue to the presence of pathology involving the orbit itself may be obtained by balloting the eye. Resistance to retropulsion usually indicates pathology within the orbit. This is particularly useful when there is asymmetry between the two sides. In addition to axial displacement of the globe forward, the globe may be displaced inferiorly (dystopia) or in or out relative to the distance from the midline of the nose. This may indicate the origin of pathology affecting the globe and other adnexal structures. Displacement inferiorly usually indicates involvement of the orbit through the roof (Fig. 5.1). Displacement of the globe medially would indicate a more central skull base pathology, often entering the orbit through the ethmoid sinus and medial wall. Involvement of the lateral wing of the sphenoid can produce both axial proptosis and displacement of the globe medially or inferiorly. Rarely, masses may actually be palpated within the orbit.

The anterior segment, including the conjunctiva, cornea, iris, anterior chamber, and lens, is best evaluated at the slit lamp. Although a penlight may be helpful, the slit lamp offers binocular magnification as well as oblique and transillumination (useful for detecting old inflammation). The pupils should be examined for irregularity and symmetry. If the pupils are unequal, they should be recorded in the light and dark. If the difference is greater in light, then the larger pupil is not constricting. Assuming there are no pharmacologic (red top dilating drops), inflammatory, or traumatic causes, one must distinguish between Adie’s pupil (postganglionic parasympathetic dysfunction, usually after viral infection or trauma, with vermiform iris movements, light-near dissociation, and tonic redilatation) and third nerve dysfunction, which should be associated with abnormal eye movements. If the pupillary difference is greater in the dark, then the smaller pupil is not dilating (Fig. 5.20). Both third nerve palsy and Horner syndrome are common symptoms of parasellar pathology affecting the cavernous sinus. A subtle dilation delay may be seen on serial photographs of the pupils taken after shutting offthe lights as a sign of sympathetic dysfunction (Horner syndrome).⁶⁹ Horner syndrome may be confirmed by a lack of dilation to cocaine drops or by reversal of anisocoria following apraclonidine (Iopidine) drops (Figs. 5.14 and 5.20). Paredrine drops will dilate the pupil of a patient with a first- or second-order Horner syndrome (brainstem, neck, or lung apex), but not a third-order Horner syndrome (seen with parasellar disease). The larger pupil due to a third nerve palsy should react to 1% pilocarpine, whereas a pharmacologically dilated pupil will not.

Fig. 5.16   A millimeter ruler can be used to measure the palpebral fissure opening.

Fig. 5.17   The upper lid range is the measurement between the lid position while the patient is looking up (A) and its changed position when the patient is looking down (B). The frontalis muscle should be splinted to more accurately measure levator function.

Fig. 5.18   The marginal reflex distance (MRD) is measured from the central corneal reflex to the upper lid margin. If this is less than 4 to 5 mm, there is evidence of ptosis.

Fig. 5.19   The Hertel exophthalmometer measures the relative distance between the lateral orbital rim and the plane of the cornea. A difference of more than 2 mm suggests either proptosis (exophthalmos) on one side or enophthalmos on the other.

Two additional critical items in adnexal assessment include evaluation of the fifth cranial nerve and lid closure. Sensation should be checked qualitatively simply by asking the patient to compare sensation in the three divisions of the distribution of the trigeminal nerve. More quantitative assessment can be obtained with an esthesiometer (Fig. 5.21), measuring corneal sensitivity. This may be particularly useful in potentially progressive lesions affecting the first division of the fifth nerve, resulting in corneal hypesthesia. A second critical function is that of lid closure. Although lid closure may be affected by proptosis alone, most of the time, marked problems with lid closure are secondary to weakness in the orbicularis muscle. Neuromuscular transmission deficits should always be considered, as should primary involvement of the orbicularis muscle itself (mitochondrial myopathy, as seen in patients with chronic progressive external ophthalmoplegia). Most weakness of lid closure, including decreased blinks and incomplete blinks, is related to facial nerve weakness. The presence of facial nerve paresis in the setting of suspected parasellar pathology would indicate much more extensive involvement or more than a single lesion.

Fig. 5.20   This 50-year-old patient presented without visual complaints but was noted to have asymmetric pupils with mild ptosis on the left side. External photographs reveal mild ptosis and anisocoria with miosis OS (A). Her past medical history was remarkable for a squamous cell mass involving her throat, and she had been treated 2 years earlier with 60 Gy of radiation therapy. CT of her neck revealed evidence of accelerated atherosclerosis of the left common carotid artery at the level of C6-7, undoubtedly related to her previous radiation therapy (B). Iopidine drops reversed the anisocoria, with a larger pupil on the left side now indicative of hypersensitivity following sympathetic denervation (C).

Fig. 5.21   The esthesiometer may be used to quantitatively assess corneal sensitivity.

Although the presence of lid retraction is most commonly seen with thyroid orbitopathy (less commonly with Collier’s sign, seen with dorsal midbrain syndrome), one important type of lid retraction occurs while the patients attempt to look down and in. This is usually seen in patients with preceding third nerve palsy and indicates aberrant regeneration of the third nerve (Fig. 5.22). Fibers that used to go to the medial rectus and inferior rectus are now misdirected to the levator. Other signs of aberrant regeneration include pupillary miosis on up and down gaze, persistent co-contraction of the superior and inferior recti (leading to restricted vertical movement), and adduction with elevation and depression. The lid elevation with depression and adduction is the most classic and obvious sign of aberrant regeneration. In rare cases, a slowly expanding parasellar lesion, such as a giant cavernous carotid aneurysm or meningioma, may produce aberrant regeneration without a history of an acute third nerve palsy. This form of “primary aberrant regeneration” is very suggestive of a slowly expanding parasellar lesion.^70,71

Relative enophthalmos is most commonly due to previous trauma, including blowout fractures of the orbit or previous hemorrhage resulting in orbital fat atrophy. Chronic inflammation of the maxillary sinus can result in enlargement of the orbit and enophthalmos (so-called silent sinus syndrome). Metastatic breast carcinoma often can produce shrinkage of the fat, resulting in a combination of enophthalmos and restricted motility.

Enlargement of the greater wing of the sphenoid, frequently related to meningioma, often presents with proptosis. However, involvement of the orbit from any direction, including through the superior orbital fissure, from and through the roof with hyperostosis, and from the sphenoid sinus and posterior ethmoids, can result in axial displacement (proptosis) as well as dystopia, with the globe displaced inferior or laterally, and less commonly medially or superiorly.

Rehabilitation

Ability to improve compromised optic nerve function is limited. Unlike goldfish, which can regrow their optic nerves, at this point we have limited options to influence the recovery of optic nerve function. It should be pointed out that visual fields often will continue to improve for periods of up to a year or more following surgical decompression of optic nerve or chiasmal compression (Fig. 5.23). This can be seen with gradual improvement in visual field function in patients with pituitary tumors following surgery.^72,73 It is likely that this functional improvement is separate from anatomic improvement because OCT thinning and optic atrophy tend to remain (Fig. 5.23). It is important to note that psychophysical functioning, electrophysiologic studies, and anatomic studies such as OCT and disc appearance, although paralleling each other, may not always be exactly linked. This is particularly obvious in patients with optic neuritis, whose central acuity and even visual fields may return to normal despite clear evidence of residual optic atrophy, OCT thinning, and electrophysiologic abnormalities, including prolonged latency on visual evoked potential. Thus, it is important to recognize that each of these assessments of afferent visual system does not replace the others.

Patients with visual impairment can be helped with various low-vision aids. These may be low-tech, including simple high-plus magnifiers that allow patients to see small objects by holding them closer, or fairly sophisticated magnification systems, including computer-driven closed circuit TV monitors. Although substantial work is being done on bionic replacement for dysfunctional afferent visual pathways, at present this is strictly theoretic and research-driven. Low-vision aids, however, can be very useful if patients can define the exact function they would like to improve. Although it is often impossible to resupply visual acuity for some of the activities of daily living, such as driving, reading can be helped, as can functioning at particular defined distances.

Visual field defects also represent a substantial challenge. Although there have been attempts at encouraging visual plasticity, it is unlikely that major field defects can be bypassed. Practice with visual field defects, however, can markedly improve the ability to read. Simple techniques such as orienting letters vertically, in the case of patients with homonymous visual field defects, can sometimes improve the ability to read,^74,75 and the use of simple tricks, such as leading the eye proprioceptively with a finger or a ruler to find the next line, can be helpful in the rehabilitation of patients with marked visual field abnormalities. High-power prisms have been used to try to bring objects into a seeing field from a nonseeing field. This has limited applicability, however, and it certainly should not be promised as a way of restoring the ability to drive to patients with dense homonymous visual field defects. They may occasionally be useful to alert patients to events in their nonseeing field.

Fig. 5.22   This 54-year-old woman was seen in March of 2009 with mild persistent double vision. On examination, she could see 20/20 bilaterally with 4-point and 3-point vision. Her visual fields were full. She did, however, have limitation in vertical gaze on the right and 1.5 mm of right ptosis, and when she looked down and to the left, her right eyelid was elevated (A). Hess screen confirmed limitation in vertical (particularly up) gaze (B). Binocular single vision fields demonstrated single vision when she looked straight ahead but double when she looked up or down (C). Eight months earlier, she had acutely developed a severe headache. CT revealed evidence of subarachnoid hemorrhage, and CTA demonstrated a right posterior communicating artery aneurysm (D).

Fig. 5.23   These are the visual fields (A,B) of a 48-year-old woman who was referred with a 1-month history of decreasing vision. Visual acuity when evaluated was 20/30 on the right and 8/200 on the left, with a 0.3 log unit afferent pupillary defect. Her funduscopic examination was unremarkable, and optical coherence tomography (OCT) demonstrated a normal nerve fiber layer (C).

Fig. 5.23   (Continued) MRI, however, revealed a suprasellar lesion compressing the chiasm and impacting both optic nerves (D,E). Her past medical history was remarkable for a 10-month history of polydipsia and polyuria, a 7-month history of amenorrhea, and a 1-month history of severe headaches, nausea, and vomiting. Transsphenoidal surgery demonstrated a craniopharyngioma, which was endoscopically decompressed. Follow-up visual fields 2 months later revealed dramatic improvement in the bitemporal defect (F,G), with visual acuity improving to 20/25 and 20/20.

Fig. 5.23   (Continued) Despite the improvement in her fields, her OCT demonstrated thinning of the nerve fiber layer nasally in both eyes (H). Follow-up 6 months after that revealed further improvement in the bitemporal visual field defects (I,J), but with some residual optic atrophy (K,L) and further thinning of the nerve fiber layer, worse on the left than the right (M).

Fig. 5.23   (Continued) Follow-up 6 months after that revealed further improvement in the bitemporal visual field defects (I,J), but with some residual optic atrophy (K,L) and further thinning of the nerve fiber layer, worse on the left than the right (M). Comment: The presence of a normal nerve fiber layer when the patient was first evaluated suggested that the compression of the chiasm was relatively acute. Recent studies suggest that this may be a good prognostic sign for improvement in both acuity and visual fields, as was the case here. Although acuity often improves immediately following decompression, visual fields may take months or more to show improvement. Despite the field improvement, however, she was left with residual optic atrophy and nerve fiber layer thinning.

Once the eye is stable, eye muscle surgery can be planned, particularly with use of the Hess screen. It is usually impossible to improve the ductions of a limited eye secondary to persistent residual cranial nerve palsy. This is particularly true in patients who develop aberrant regeneration of the third nerve. In this, persistent co-contraction of the superior and inferior rectus muscles limits vertical excursion. As it is impossible to rewire the eye, the only way of increasing binocularity is to limit the movement of the better-moving eye. Although this takes some explaining to the patient and family, it is possible to increase the area of binocularity and reduce diplopia. This is best accomplished through the use of posterior fixation sutures (Faden procedure), in which a combination of recessing the muscle and adding sutures placed well posteriorly limits the overall excursion of the better-moving eye (Fig. 5.24). Again, it is essential to make sure the eye is stable before this sort of intervention is considered.

In the setting of a complete sixth nerve palsy, to provide a tonic abducting force, a transposition procedure can be accomplished, moving the superior and inferior rectus muscles to the insertion of the lateral (Fig. 5.25). This may be done as a full-thickness transposition or as a partial-thickness transposition, which may potentially spare some of the circulation to the anterior segment. The presence of pulleys controlling the position of the muscles⁷⁶ limits the extent of transposition, and an important recent modification of this technique involves the use of posterior fixation sutures along the area of the globe equator. This moves the effectiveness of the transposition more posteriorly and results in a greater abducting effect than does a simple transposition procedure alone. This so-called Foster modification is part of the routine in moving the eye out following a complete sixth nerve palsy. A similar procedure may be used in the absence of elevation (double elevator palsy), in which the medial and lateral rectus muscles are moved superiorly to act as elevators. The pulley system controlling the extraocular muscles again limits the amount of transposition possible. Decisions about the type of extraocular muscle surgery usually depend on whether or not the defect is complete. In the setting of a complete sixth nerve palsy, the usual sequence would be to perform a transposition procedure to give some tonic abduction to the eye, followed by limiting procedures on the opposite yoke muscle (the medial rectus in the opposite eye). In the setting of an incomplete sixth nerve palsy, weakening of the medial rectus in the opposite eye, which would include a recession procedure and Faden operation, would be the primary surgical intervention. This can later be fine-tuned by a recession and resection of the various muscles on the involved side to move the eye into better alignment. It is also important to recognize that any subtle residual defect can be managed with prism in glasses, although ground-in prism is limited to approximately 6 degrees of malalignment (12 diopters of ground-in prism). Although larger Fresnel prisms may be applied to the glasses, these usually degrade acuity by blurring visual function. They are often not tolerated for lengths of time but can be tried as a temporary measure.

Adnexal Rehabilitation

Probably the most important aspect of adnexal rehabilitation is to provide for adequate lid function. In the setting of a seventh nerve palsy, it is critical to ensure lid closure to avoid neuroparalytic keratitis. Short-term measures include aggressive lubrication, including ointment at nighttime, and potentially taping the eye at night. During the day, adequate lubrication without blurring of the vision can be obtained with semiviscous solutions such as Refresh Liquigel and GenTeal Gel. Partial tarsorrhaphies or even central tarsorrhaphies can protect the globe in the short term if the patient has epithelial breakdown, particularly in the setting of combined facial nerve palsy and trigeminal nerve palsy. Failure of seventh nerve function to recover usually requires surgical intervention to help close the lid. Although it is still possible to implant an elastic band (Arion sling) or springs, the easiest way to help lid closure is with gravity assist by implantation of a gold or platinum weight. Although some weights can be applied externally, most of these are usually implanted in a pretarsal or, less commonly, preseptal location. Although the preseptal implants are less obvious cosmetically, they tend not to be as effective. Some surgeons will use a single-size weight, but it is usually advisable to tailor the gold weight to the particular status of the patient. I prefer to implant the heaviest weight that the patient can easily lift up, producing a minimal amount of ptosis. The heavier the weight, the more likely are good lid closure and eye protection. It is imperative to note that patients who are otherwise compromised and therefore supine in bed should never have a gold weight implanted because they cannot sit up to allow gravity to have an appropriate effect. In that setting, it is often better to simply perform a tarsorrhaphy to protect the eye.

Fig. 5.24   In June of 2007 a 50-year-old woman was referred for diplopia. Her acuity and visual fields were normal, but she had evidence of an abduction deficit on the left side (A) with an esotropia increasing on left gaze (B). Binocular single vision fields (C) confirmed diplopia on left gaze. Seven months earlier, she had begun to have episodes of “voices in my head.” EEG demonstrated an epileptogenic focus, and MRI in April had revealed a sphenoid wing meningioma (D,E).

Fig. 5.24   (Continued) In June of 2007 a 50-year-old woman was referred for diplopia. One month later, she had undergone pterional craniotomy and tumor resection. Repeat MRI demonstrated damage to the left lateral rectus muscle (F,G). One year later, when her motility failed to improve spontaneously, she underwent a right medial rectus recession and Faden procedure. This limited the adduction on the right to match the limited abduction on the left (H) and completely eliminated her double vision (I). Comment: With both paretic and restrictive causes of limitation in motility, it is often impossible to improve ductions. Although the eye can be straightened in primary position to maximize binocularity, surgery on the contralateral eye may be advisable.

Fig. 5.25   This 48-year-old patient noted some ringing in her ears, and MRI demonstrated a parasellar right cavernous meningioma. She underwent pterional craniotomy and resection, which left her with a right IV, V, and VI cranial nerve palsy. Immediately following surgery, the abduction deficit could be seen on her nine cardinal positions (A), and the Hess screen (B) confirmed a problem with abduction. There was no recovery of nerve VI, and by 4 months following surgery she had developed 50 diopters of right esotropia (C). She was treated with injection of 5 units of Botox into the right medial rectus muscle, which resulted in a decrease in adduction on the right (D) as well as some inadvertent problems with down gaze on the right side, but her right eye did not deviate out at all, indicating that her nerve VI was still complete.

Fig. 5.25   (Continued) This 48-year-old patient noted some ringing in her ears, and MRI demonstrated a parasellar right cavernous meningioma. She underwent pterional craniotomy and resection, which left her with a right IV, V, and VI cranial nerve palsy. As the Botox began to wear off, the right eye began to drift back in (E). Botox was reinjected into the right medial rectus muscle, and the patient underwent a full tendon transfer of the right superior and right inferior rectus muscles to the origin of the lateral rectus along with a posterior fixation suture (Foster modification), which substantially straightened her eye (F). Seven months later, she had an area of binocularity centrally, although she still had double vision when she looked down, left, or right (G,H).

Fig. 5.25   (Continued) This 48-year-old patient noted some ringing in her ears, and MRI demonstrated a parasellar right cavernous meningioma. She underwent pterional craniotomy and resection, which left her with a right IV, V, and VI cranial nerve palsy. Seven months later, she had an area of binocularity centrally, although she still had double vision when she looked down, left, or right (G,H). This has remained stable (I), and when seen 30 months following her strabismus surgery, she still had an area of binocularity centrally and was pleased with her ability to function (J,K). She was noted to have some redness in the right eye due to neurotrophic changes because of the loss of normal sensation. Comment: The patient was made functional here by muscle transposition surgery. She remains at risk because of the lack of fifth nerve innervation and therefore can easily develop epithelial breakdown. It is imperative that these patients be followed carefully.

Exacerbation of Ophthalmic Findings Following Surgical Intervention

The potential for injury of the afferent and efferent visual pathways with transcranial surgery depends on the approach. A transfrontal approach can result in injury to the optic nerves and chiasm and frequently cause problems with the olfactory nerve. A pterional approach can injure the optic nerve, particularly during a takedown of the anterior clinoid (especially if this is done extradurally). Aggressive surgery in the area of the cavernous sinus, of course, can result in compromise of the third, fourth, and sixth cranial nerves, but also the fifth nerve, producing neurotrophic problems (Fig. 5.25). Aggressive retraction of the scalp flap can injure branches of the seventh nerve, and although this usually causes brow ptosis alone, it can theoretically compromise lid closure. The burr hole placed at the pterion can be misdirected into the orbit, producing damage to the superior rectus and levator muscles (resulting in ptosis and diplopia), or to the lateral rectus (Fig. 5.24). Overly aggressive retraction of the temporal lobe during a pterional approach can produce secondary ischemia and infarction, compromising the visual pathways within the temporal lobe and resulting in homonymous hemianopsia, usually superior and incongruous, secondary to involvement of Meyer’s loop.

Radiation therapy can result in delayed radiation optic neuropathy, usually appearing 6 months to 2 years following fractionated radiation therapy. This often presents with the sudden onset of altitudinal visual field loss followed by central acuity loss. Magnetic resonance imaging (MRI) findings include enhancement of the optic nerve extending to the chiasm. Radiosurgery with the gamma knife, Cyber Knife, or modified linear accelerators (LINAC) may result in acute necrosis, which can involve the optic nerve, chiasm, or optic radiations in the temporal lobe.⁷⁷ Stereotactic radiosurgery that encompasses the cavernous sinus has a small but not insignificant incidence of worsening of ocular motor palsies.

Conclusion

The neuro-ophthalmic evaluation is an essential part of the assessment of any patient suspected of having a parasellar lesion. Although there is a tendency to believe that the clinical evaluation has been replaced by imaging, it is usually the examination that leads to appropriate imaging, and it clearly is quantitative assessment in the evaluation that will determine whether or not lesions are changing (natural history), even when the imaging studies remain the same. This can be an important indicator for intervention and may also be used to follow patients after intervention to determine whether that intervention, be it medical treatment, surgery, or radiation, has been effective. The psychophysical testing of the neuro-ophthalmic evaluation is far better attuned to what our patients experience than any of the radiologic or anatomic studies that may indicate disease. As such, determining what our patients see and how their eyes move and function is a critical part at all stages in following those with parasellar pathology.

Appendix I: The Neuro-ophthalmic Examination for the Neurosurgeon

Testing points: Test each eye separately, making sure that the opposite eye is occluded. Encourage patients to guess. Ensure adequate lighting. Watch out for the ability to read only the last letters because this may indicate a visual field defect. Use a 200 E (Fig. 5.26) to quantitate acuity less than 20/400, reporting the distance at which the patient can see the direction in which the E is pointed. Patients should be allowed to hold the E in any position they like (make sure the opposite eye is covered) to avoid visual field defects. Test patients who cannot see the 200 E at any distance for “hand motion”; determine the direction in which the tester’s hand is moving. If hand motion is not present, determine if the patient can perceive light (“light perception”) and its direction (“with projection”).

Near Vision

Requirements: Use of a near chart (Fig. 5.7), near refractive correction (or add), measurement of distance at which the card is held.

Testing points: Make sure each eye is tested separately. Make sure the patient is wearing appropriate near correction. Allow patients to hold the reading material at the distance at which they see most clearly. Measure the distance to the near chart. Record the near acuity in the point system. If no correction is available, have a plus lens (usually +2.50 to +3.50) to put in front of the patient’s eye to ensure that the patient is adequately corrected for near.

Fig. 5.26   A 200 optotype E (9 cm in size) can be held at the farthest distance at which the patient can identify the direction in which the E is pointed. Ideally, patients will hold the card themselves. This permits quantitative assessment of acuity of less than 20/400, and is more quantitative and reproducible than “count fingers.”

Testing points: Subtle washout of colors can be recorded as a substitute if formal color vision testing is not available by comparing colored (usually red) test objects (Fig. 5.27).

Fig. 5.27   Subtle optic nerve dysfunction may be appreciated as dimming or desaturation of a red test object. This is particularly useful for comparing the two eyes and may also be used to pick up subtle visual field defects by comparing red test objects across the vertical midline.

Requirements: Special contrast sensitivity testing, including the Vistech system, sinusoidal gradings, and Pelli-Robson charts. Adequate lighting and appropriate refractive correction are critical.78

Testing points: Subtle abnormalities in contrast sensitivity may be detected following previous damage to the optic nerves even when Snellen acuity is normal.

Stereo Acuity

Requirements: Stereo testing can be done with the Titmus test and Randot test; usually, polarized glasses are used (Fig. 5.28). Fusion and fusional amplitudes can be measured with an amblyoscope.

Testing points: The presence of normal stereopsis indicates that both maculae are working well. This is a triple check on the previous Snellen vision and near vision.⁷⁹

Visual Field Testing

Requirements: Central scotomas in particular can be picked up on Amsler grid testing (Fig. 5.29), in which patients are given a grid and asked to look at the center dot and describe whether parts of the grid are missing. A response of distortion of the lines is particularly seen in patients with macular disease. Qualitative perimetry may include Amsler grid testing and confrontation testing (Fig. 5.28), in which fingers are counted (one, two, or five) at an equal distance from the patient, allowing the observer to compare his or her own field with the patient’s field.80 This should be done monocularly. A moving or waving target can also be used to pick up dense defects. The visual fields of patients who are confined to bed may be tested by projecting a target with a laser pointer on the ceiling. This can be presented statically (on/off) or kinetically (moving from periphery to the center). Semiquantitative testing may be obtained by using a tangent screen on which variously sized test objects are moved from nonseeing to seeing kinetically or presented statically by flipping them over. Comparison testing across the vertical midline, particularly of red test objects, may pick up subtle desaturation. This can also be used across the nasal horizontal midline. Simultaneous appearance in both hemifields can pick up subtle neglect due to higher cortical dysfunction. Quantitative visual field testing usually involves dedicated apparatus, either kinetic (Goldmann bowl perimeter) or static (Humphrey, Octopus automated static perimetry). Because of longer time and duration, static perimetry in particular is often concentrated centrally, although peripheral testing is possible when indicated.

Testing points: Visual field testing is required to assess extrafoveal function. Three anatomic correlates of visual fields emphasize the importance of testing centrally across the nasal horizontal midline and across the vertical midline.

1. The small fibers responsible for central vision are partially sensitive to macular disease and certain optic neuropathies, particularly metabolic, hereditary, toxic, compressive, or inflammatory etiologies. Thus, these lesions (including compressive lesions) tend to cause central scotomas. Most central scotomas are related to macular disease.
   
2. The disc is located nasal to the fovea (arcuate visual field defects are an indicator of optic nerve pathology).⁸¹
   
3. The visual pathways segregate left and right information at the chiasm (visual field defects that respect the vertical midline indicate chiasmal and retrochiasmal involvement).

Therefore, all visual field tests should be designed to detect central scotomas, field defects that respect the nasal horizontal midline, and field defects that respect the vertical midline. Visual field testing should be thought of as qualitative (looking to detect the presence of an abnormality in the visual field) versus quantitative (looking for how much of a visual field defect there is). Field testing is divided into kinetic perimetry, in which a fixed-intensity target is moved from areas of nonseeing to areas of seeing, and static, in which a fixed location is tested with an increasingly intense stimulus.

Fig. 5.28   The Titmus test can be used to detect stereoacuity. Normal stereopsis requires bilaterally good acuity. Stereoacuity may be absent in the setting of amblyopia, strabismus, or monofixation syndrome.

Fig. 5.29   An Amsler grid is very useful for picking up subtle distortion, which may be seen with macular disease, but it may also detect early visual field abnormalities, particularly if the patient is asked to compare parts of the grid across the vertical and nasal horizontal midline.

Requirements: Fixation target so that accommodation does not change (patient should be instructed to fixate on a distant target, not just a light or “my nose”). An external camera can document pupil size in varying illumination. A bright light (not enough to produce an aversive response but bright enough to ensure adequate pupillary reactivity), such as a muscle light or indirect ophthalmoscope, should be used. A pupil gauge or ruler can quantitatively measure pupil size. A neutral-density filter bar can be placed in front of the better-functioning eye to grade an afferent pupillary defect (Fig. 5.9).

Testing points:

1. Pupils should be examined in both light and dark with a pupil gauge or millimeter ruler; the examiner should look for subtle asymmetry in pupil size. Subtle asymmetry is common (essential anisocoria may occur in >50% of the population when a 0.2- to 0.3-mm difference is looked for).
   
2. Anisocoria that increases in the dark usually indicates that the smaller pupil is not dilating and may be an indicator to check locally for inflammation, and also for Horner syndrome.⁶⁹ Anisocoria that increases in the light suggests that the larger pupil is not constricting and usually is an indicator to check both locally for evidence of inflammation, synechiae (best seen by slit lamp), a history of the use of eye drops, and also the possibility of motility disturbance that would parallel a third nerve palsy. Vermiform movements of the iris (best seen at the slit lamp) may indicate an old Adie syndrome due to involvement of the ciliary ganglion.
   
3. In a test for an afferent pupillary defect, patients should fixate an accommodative distance target. The examiner should move the bright test light quickly from one eye to the opposite eye, looking for initial contraction and release. Any asymmetry can be quantitated further by placing neutral-density filters in front of the better-reacting pupil.⁵⁰ Important point: An afferent pupillary defect may be detected even when only one pupil is working.
   
4. Pupils that do not react to light should be tested for response to a near target accommodation. Light-near dissociation may be seen in patients with any of the following: previous laser treatment of the eye, Adie syndrome (due to pathology affecting the ciliary ganglion), complete optic neuropathies in which they still retain pupillary response when given a proprioceptive near target, or dorsal midbrain pathology.

Assessment of the Efferent System

Ocular Motor Stability

Requirements: A direct ophthalmoscope (Fig. 5.11) is a very sensitive means of assessing stability of the eyes in primary and eccentric gaze.⁵⁵ More quantitative analysis of eye stability, as well as spontaneous and voluntary movements, can be obtained with infrared tracking, video monitoring, EOG, or electromagnetic coil recording.⁵⁶

Testing points:

1. Eyes should be examined for stability in primary position. Spontaneous eye movements may indicate underlying pathology affecting the ocular motor pathways. Small conjugate refixation movements are normal (square wave jerks). An increase in their amplitude (better seen on funduscopic examination with a direct ophthalmoscope) may indicate cerebellar pathology. Tendencies for the eyes to spontaneously drift in a conjugate direction may be a sign of congenital nystagmus but also may develop following asymmetric vestibular pathology. Stability in primary position but drift back to the center when the patient looks eccentrically usually indicates pathology affecting the neural integrator (gaze paretic nystagmus). This can be best seen during subtle movement of the eye following dilation by using a direct ophthalmoscope but is often picked up easily simply by direct observation. Neural integrator pathology may be seen with intoxication, antiseizure medications, sedatives, and metabolic abnormalities.
   
2. Quantitative assessment may be obtained with ocular motor recordings that use infrared tracking, EOG, or ocular search coil technology.

1. The vestibular ocular reflex may be tested by viewing the disc while rotating the patient in the dark. If the disc moves off fixation, the vestibular ocular reflex gain has been affected. Subtle abnormalities in vestibular ocular reserve may be detected by having patients shake their head from side to side in the dark and open their eyes while the examiner observes the disc for a drift to one side. Drift induced by head shaking suggests asymmetric vestibular reserve, often seen in patients with old vestibular pathology (eg, acoustic neurinoma).
   
2. The saccadic system may be tested by having patients move their eyes from one target to another.82 Characteristics of normal saccades include latency (usually 250 milliseconds between when the patient is instructed to move and the movement), velocity (which can be estimated by simply looking at the saccades [the larger the saccade, the faster the peak velocity] or quantitatively by ocular motor recording), and accuracy (whether or not the saccades reach their target). If they undershoot and drift in (glissade) or overshoot and then achieve alignment by a second saccade, the saccades are said to be dysmetric. Saccadic dysmetria suggests cerebellar pathology. Problems with initiation of saccades can be seen congenitally (ocular motor apraxia) or with frontal lobe pathology. Slowing of saccades is usually a sign of burst cell pathology (paraneoplastic) but may also be seen with primary muscle disease (chronic progressive external ophthalmoplegia, mitochondrial myopathy).
   
3. The pursuit system can be tested by having the patient fixate a small accommodative target that moves (should not be any faster than about 30 degrees per second). Another subtle means of testing pursuit is to have patients fixate a thumb while rotating in a chair (Fig. 5.30). As the vestibular system would normally move their eyes in the opposite direction to which they are rotated, keeping their eyes on the thumb indicates that the vestibular reflex can be canceled. This usually indicates an intact pursuit system. Interruption by saccades (“cogwheel pursuit”) suggests pathology affecting the pursuit system somewhere between the middle temporal gyrus and the pontine nuclei.
   
4. The convergence system can be tested by having the patient look between a distant and a near accommodative target. Failure of convergence may be seen by the development of an exodeviation at near. Lack of effort or cooperation may be suspected if there is failure of miosis, which should accompany convergence.

Fig. 5.30   Subtle abnormalities in the pursuit system may be detected by rotating patients while observing their ability to maintain fixation on their thumb.

Requirements: Qualitative malalignment21 may be directly observed, noted by asymmetry of the corneal light reflex (Hirshberg), or identified by dissociative testing (red glass, Maddox rod; Fig. 5.12). Quantitative measurements may be made with prisms or on an amblyoscope. Dissociative tests such as the Maddox rod can be quantitated by adding prisms. The Hess screen⁶¹ and binocular single vision assessed with a Goldmann bowl can further quantitate relative movements of the two eyes. Malalignment due to restrictive pathology may be separated from paretic problems by forced duction testing (anesthetic, forceps, suction cup^62,83) or measurement of intraocular pressure in eccentric gaze (pneumotonometer, Tonopen).

Testing points: Ductions can be assessed qualitatively by determining whether the eye crosses midline and whether it reaches appropriate eccentric gaze. The easiest clue to an abnormality in ductions is provided by asymmetric movement of the eyes. Ductions can be further quantitated with a linear ruler measurement, prisms, or most quantitatively with a Goldmann bowl. Versions are movements of the eyes relative to each other. They can be qualitatively noticed if there is adducting or abducting delay or if one eye reaches the desired position more quickly than the opposite eye. This will also be seen as malalignment. Malalignment may be measured qualitatively by using a red glass or a Maddox rod test,57 or quantitatively by using a Hess screen61 and cross-cover testing with prisms. Maddox rod permits easy demonstration of incomitant deviations (does not distinguish between paretic and restrictive causes) and allows critical identification of the direction of maximal deviation and also of minimal deviation.

Adnexal Evaluation

Basic Adnexal Evaluation

Requirements: A ruler is critical for measurements of the palpebral fissures (Fig. 5.16), upper lid range (Fig. 5.17), and orbital symmetry. External photographs are very useful for documenting adnexal anatomy. A Hertel apparatus can be used to determine proptosis (Fig. 5.19). Sensation can be qualitatively evaluated with a cotton tip or quantitatively with an esthesiometer (Fig. 5.21). Sophisticated orbital evaluation can be done with an ultrasound (Fig. 5.2).

Testing points:

1. The patient’s face should be examined for symmetry. Often, one eye is slightly higher than the other, and this should be recorded.
   
2. The distance between the upper and lower lids should be recorded bilaterally as the palpebral fissure opening.
   
3. The distance from a light reflex in the center of the pupil to the upper lid should be recorded as the marginal reflex distance (Fig. 5.18).
   
4. Excess skin on the upper lid may be recognized as dermatochalasis, which can become clinically significant if it droops over the lid margin.
   
5. Normally, the lids will cross the limbus both superiorly and inferiorly. Being able to see the sclera between the limbus of the cornea and the lid indicates lid retraction. This can be both superior and inferior.
   
6. Levator function is recorded by splinting the frontalis muscle and having the patient look way up and way down.
   
7. Relative proptosis can be seen qualitatively by looking over the patient’s forehead and quantitated by using a Hertel apparatus.
   
8. Facial sensation should always be checked, with the examiner looking for symmetry.
   
9. Blinks should be assessed for both frequency and completeness. Patients who have incomplete blinks should be examined for their ability to close completely. Failure to close completely (lagophthalmos) is often associated with corneal exposure problems.
   
10. Orbicularis strength can be qualitatively assessed and the two sides compared.
    
11. Spontaneous movement of the face (blepharospasm, hemifacial spasm, facial myokymia, benign facial fasciculations) may also be recorded.

Adjunctive Adnexal Assessment

Requirements: High-tech equipment for examining the orbit and adnexal structures include a slit lamp, ultrasound, OCT unit (for both anterior and posterior segment evaluation), and fundus cameras.

Testing points:

1. Patients with pathology within the orbit may have abnormal resistance to retropulsion. This is tested by ballottement.
   
2. Auscultation of the orbit may also be obtained and can demonstrate a bruit in the setting of a carotid cavernous fistula.
   
3. The anterior segment may be assessed, ideally with a slit lamp providing illumination from the side so that the various levels of the globe can be evaluated. A pen light examination can reveal abnormalities in the cornea, anterior chamber, iris, and lens.
   
4. Funduscopic examinations should concentrate on the disc, macula, and posterior pole structures. The disc should be evaluated for size and symmetry, cupping, abnormal blood vessels, elevation or hyperemia, hemorrhage, exudate, and the possible presence of optic atrophy. The macula should be evaluated for thickening, hemorrhage, and exudate. Vessels should be inspected for narrowing or dilatation as well as tortuosity, anomalies, crossing changes (where the artery crosses the vein), and irregularities in the wall. Other posterior pole pathology includes new vessels (neovascularization) and obstruction of vessels, including Hollenhorst plaques, loss of nerve fiber layer, inflammatory infectious pathology, and various degrees of hemorrhage. Hemorrhage may be under the retina, in the retina (flame-shaped or dot-blot), in front of the retina (preretinal, subhyaloid), or in the vitreous (Fig. 5.31). The retina may be elevated by traction (following trauma or related to diabetes) or underlying fluid (rhegametogenous—due to a hole or related to exudate). Mass lesions (inflammatory or neoplastic) may be located in the choroid (subretinal) or retina, or may extend into the vitreous. Funduscopic evaluation can be greatly improved by dilating the patient’s pupils. A nonmydriatic fundus camera may also be a useful way of seeing the posterior globe better.
   
5. Ultrasound may record the size of the extraocular muscles and the possible presence of intraorbital mass lesions.

Fig. 5.31   This 52-year-old man presented with the acute onset of the “worst headache of his life” and severe blurred vision. CT showed evidence of an aneurysm at the skull base (A) in the distal vertebral artery with a dissection extending into the basilar artery and subarachnoid hemorrhage. Funduscopic examination revealed evidence of bilateral preretinal, interretinal, and subretinal hemorrhage related to an acute increase in intracranial pressure (B,C). The patient’s Terson syndrome resolved over 6 months, with a return in visual acuity from the 20/400 when he was first seen to 20/30 and 20/40. Comment: Terson syndrome is vitreous hemorrhage associated with a subarachnoid hemorrhage. Most cases occur in the setting of a ruptured intracranial aneurysm. The hemorrhage may often clear spontaneously over weeks to months. Those that fail to clear may be treated with vitrectomy.

Appendix II

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