Examination of Eye Movements
PURPOSE
The main purpose of the examination of eye movements is to look for evidence of dysfunction of the third or sixth cranial nerves, the extraocular muscles, or the brainstem. Another purpose of the eye movement examination is to assess the function of the central nervous system pathways that control voluntary conjugate gaze of the eyes.
WHEN TO TEST EYE MOVEMENTS
Eye movements should be examined in all patients as part of a standard neurologic examination.
NEUROANATOMY OF EYE MOVEMENTS
Cranial Nerves and Extraocular Muscles
The movements of each eye are directly due to the action of the six extraocular muscles that attach to the globe. Innervation to these extraocular muscles comes from three cranial nerves: the oculomotor (third) nerve, the abducens (sixth) nerve, and the trochlear (fourth) nerve. Table 14-1 summarizes the cranial nerve innervation to the extraocular muscles and the principal action of each muscle.
Central Nervous System Pathways for Voluntary Control of Gaze
Voluntary control of gaze occurs because of pathways that arise in the cerebral hemispheres and descend into the brainstem, ultimately controlling conjugate gaze through their action on the cranial nerve nuclei in the brainstem. Horizontal gaze (the most clinically important pathway to know about) is initiated by impulses from the “frontal eye field” of each cerebral hemisphere that project to the contralateral pons.
EQUIPMENT NEEDED TO EXAMINE EYE MOVEMENTS
None.
HOW TO EXAMINE EYE MOVEMENTS
Stand in front of the patient, holding your index finger approximately 1 ft or more away from the patient, holding the finger up vertically, midline between the patient’s eyes.
Ask the patient to follow your finger with his or her eyes while keeping his or her head still. It sometimes helps to hold the patient’s head still by gently resting your other hand on the patient’s head or under the patient’s chin.
Smoothly move your finger across to your right to observe the patient’s horizontal eye movements toward the left.
Then smoothly move your finger across to your left to observe the patient’s horizontal eye movements toward the right.
TABLE 14-1 Summary of the Innervation and Principal Actions of the Extraocular Muscles
Cranial Nerve
Origin of
Cranial Nerve
Extraocular
Muscles Innervated
Principal Action
of Muscle
III (Oculomotor)
Midbrain
Superior rectus
Inferior rectus
Medial rectus
Inferior oblique
Moves eye up
Moves eye down
Moves eye medially
Moves eye up (best when eye is in adducted position)
IV (Trochlear)
Midbrain
Superior oblique
Moves eye down (best when eye is in adducted position)
VI (Abducens)
Pons
Lateral rectus
Moves eye laterally
Move your finger back to the midline so that the patient’s eyes follow back to the midline.
Change the orientation of your index finger so that it is now horizontal.
While your finger remains in the midline (between the patient’s eyes), move your finger smoothly up to assess the patient’s vertical upward eye movements.Related posts:
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