The main purpose of the examination of visual acuity during the neurologic examination is to determine how well the optic nerves are functioning.

Visual acuity should be assessed during the neurologic examination if the patient has any visual symptoms or if the patient is thought to have a condition that can ultimately affect vision. In the absence of these situations, it is not imperative to check visual acuity in all patients as part of a routine neurologic examination.

Visual acuity of each eye depends on the integrity of the eye (anterior compartment and posterior compartment, including the retina) and the optic nerve. Lesions posterior to the optic chiasm affect visual fields (see Chapter 13, Visual Field Examination) but do not cause abnormal visual acuity within the intact fields.