Stroke This occurs when interruption of blood supply from the posterior cerebral artery to the visual cortex is prolonged. The only finding on examination is a homonymous visual field defect that stops abruptly at the vertical meridian. Occipital lobe stroke is usually due to thrombotic occlusion of the vertebrobasilar system, embolus, or dissection. Lobar hemorrhage, tumor, abscess, and arteriovenous malformation are other common causes of hemianopic cortical visual loss. Factitious (Functional, Nonorganic) Visual Loss This is claimed by hysterics or malingerers. The latter comprise the vast majority, seeking sympathy, special treatment, or financial gain by feigning loss of sight. . | Chapter 029. Disorders of the Eye Part 14 Stroke This occurs when interruption of blood supply from the posterior cerebral artery to the visual cortex is prolonged. The only finding on examination is a homonymous visual field defect that stops abruptly at the vertical meridian. Occipital lobe stroke is usually due to thrombotic occlusion of the vertebrobasilar system embolus or dissection. Lobar hemorrhage tumor abscess and arteriovenous malformation are other common causes of hemianopic cortical visual loss. Factitious Functional Nonorganic Visual Loss This is claimed by hysterics or malingerers. The latter comprise the vast majority seeking sympathy special treatment or financial gain by feigning loss of sight. The diagnosis is suspected when the history is atypical physical findings are lacking or contradictory inconsistencies emerge on testing and a secondary motive can be identified. In our litigious society the fraudulent pursuit of recompense has spawned an epidemic of factitious visual loss. Chronic Visual Loss Cataract This is a clouding of the lens sufficient to reduce vision. Most cataracts develop slowly as a result of aging leading to gradual impairment of vision. The formation of cataract occurs more rapidly in patients with a history of ocular trauma uveitis or diabetes mellitus. Cataracts are acquired in a variety of genetic diseases such as myotonic dystrophy neurofibromatosis type 2 and galactosemia. Radiation therapy and glucocorticoid treatment can induce cataract as a side effect. The cataracts associated with radiation or glucocorticoids have a typical posterior subcapsular location. Cataract can be detected by noting an impaired red reflex when viewing light reflected from the fundus with an ophthalmoscope or by examining the dilated eye using the slit lamp. The only treatment for cataract is surgical extraction of the opacified lens. Over a million cataract operations are performed each year in the United States. The operation is generally .
