Visual Consequences of Optic Tract Damage

Abstract

Background: Optic tract lesions can have devastating visual consequences. When insult is isolated to the optic tract, central acuity is typically spared and color vision is usually normal; the visual manifestation of damage is a visual field deficit. Optic tract damage as a cause for homonymous hemianopia is relatively rare compared to other visual pathway lesions producing such a field defect, and presents with characteristic features. These features include a relative afferent pupillary defect in the eye contralateral to the lesion and pallor of that optic disc in a “band” or “bow-tie” configuration. Case Reports: Two patients with optic tract damage of different etiologies were examined. The first patient presented with concerns about blackouts and peripheral field deficits. Neuroimaging demonstrated a supersellar meningioma compressing the left optic nerve and part of the optic tract. Prior to meningioma resection, threshold visual field testing revealed the presence of a right incongruous incomplete homonymous hemianopia. The second patient sustained severe brain injury during a motor vehicle accident which left him in a coma for over one month. Upon awakening, he reported left-sided vision loss. Magnetic resonance imaging revealed damage involving the right optic tract, corresponding with a left homonymous hemianopia found on threshold perimetry. Conclusions: The optometrist should bear in mind that homonymous hemianopic visual field deficits can be caused by lesions in the optic tract, although damage to this portion of the visual pathway occurs infrequently. The unique clinical presentation of optic tract lesions enables the optometrist to make a preliminary diagnosis as to the location of the insult. This is especially important since lesions of the optic tract may be difficult to detect with neuroimaging. CE Notification: This article is not available as a COPE accredited CE course. To view all the COPE accredited CE courses: Click here to Enroll (https://www.crojournal.com) Please check COPE course expiry dates prior to enrollment. The COPE course test must be taken before the course expiry date