A 67-year-old woman visits the clinic because she has observed diminished vision in her right eye for the last week. The patient claims that her right eye's vision is "narrower" than her left. Her medical history is notable for hypertension, type 2 diabetes, and hyperlipidemia. She also has intermittent lower limb claudication and has experienced two previous instances of transitory vision loss in her right eye. A right nasal hemianopia is shown by visual field testing. A right internal carotid artery aneurysm is discovered during a head and neck MRI/magnetic resonance angiography. Which of the following visual pathway segments is most likely disturbed in this patient?

Question

Quizplus · Accepted Answer

Eductional Objective: Humans have a maximum horizontal field of vision with both eyes of around 200 degrees. The binocular field of view (stereoscopic vision) is made up of the middle 120 degrees, with two side fields of around 40 degrees viewed by only one eye (monoscopic vision). Unilateral visual abnormalities within the binocular field of view (such as unilateral nasal hemianopia) may be disguised by the normal eye and hence go unreported by the patient.
Light reaches the temporal side of each retina, and optic nerve fibers from the temporal section of the retina migrate laterally via the optic chiasm to enter the ipsilateral optic tract. Lesions involving the lateral aspects of the optic chiasm can cause ipsilateral nasal hemianopia by damaging these uncrossed, temporal retinal fibers. This may occur with aneurysm of the internal carotid artery (eg, cavernous or ophthalmic segments), as seen in this patient.

A 67-Year-Old Woman Visits the Clinic Because She Has Observed