Man presents with dark spot in peripheral vision
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A 62-year-old man presented to the New England Eye Center comprehensive ophthalmology clinic for an urgent evaluation of a black shadow in the inferotemporal field of his left eye that started suddenly 4 days prior while he was sitting. He did not have any pain, flashes, floaters, decrease in central vision, field loss in the right eye or injection. He otherwise felt well. The shadow moved slightly when he moved his head from left to center, and it was more prominent in brighter lighting. His ocular history included a right superotemporal operculated retinal hole with vitreous hemorrhage, for which he underwent laser retinopexy 6 years prior. He had not followed up for routine eye care since that time.

On examination, the patient’s best corrected visual acuities were 20/25-2 in the right eye and 20/25+2 in the left eye. Pupils were equal in size and reactive to light with no relative afferent pupillary defect. IOPs were 13 mm Hg bilaterally. Confrontation visual fields were full. Extraocular motility was full bilaterally. Given the unremarkable dilated examination and visual field testing showing a left homonymous visual field loss, there was a concern for an intracranial process posterior to the optic chiasm on the right side. The differential diagnosis for this patient included ischemic or hemorrhagic cerebrovascular accident (CVA), tumor, arteriovenous malformation, and trauma. The most common cause of a homonymous hemianopia in an adult is an ischemic stroke. Because this patient had a mechanical mitral heart valve and a history of an opiate use disorder, there was concern that he could be embolizing from the valve either from a platelet thrombus or endocarditis vegetation.

CT of the head showed gray-white matter indistinction involving the medial right occipital lobe, concerning for a stroke. Because the onset of vision loss was 4 days prior, the patient was not a candidate for tissue plasminogen activator (tPA) treatment, which is typically given 3 to 4.5 hours after the onset of symptoms. He was admitted for further workup.

Subsequent MRI of the brain showed restricted diffusion of the medial right occipital lobe in the posterior cerebral artery (PCA) territory, compatible with an early subacute infarct. Additionally, there were several remote lacunar infarcts of the left cerebellar hemisphere as well as left inferior frontal gyrus encephalomalacia. CT angiography of the neck did not show any carotid or other large vessel stenosis, occlusion or dissection. An EKG showed normal sinus rhythm. HbA1c was 5.9% (in the prediabetic range), and low-density lipoprotein cholesterol was mildly elevated at 146. His international normalized ratio (INR) was 1.3, whereas the goal in the setting of a mechanical heart valve was 2.5 to 3.5. The patient was started on enoxaparin sodium injections until his INR was in the therapeutic range. A transthoracic echocardiogram did not show any vegetations or thrombus on the mechanical heart valve. Ultimately, it was thought the etiology of the strokes was most likely to be cardioembolic events from the patient’s mechanical valve in the setting of a subtherapeutic INR. The patient was discharged on a new warfarin regimen with close follow-up for INR monitoring. He was also started on a statin.

At follow-up in the neuro-ophthalmology clinic 4 weeks after discharge, the patient mentioned that the visual field loss appeared to be smaller. Repeat Humphrey visual field testing confirmed that the left homonymous inferior quadrantanopia had improved.