Initial presentation

A 60-year-old man had a 2-week history of daily recurrent episodes of transient, painless vision loss, each lasting 3–5 s. He had attended ophthalmology for years because of intermittent diplopia, and a history of type 1 diabetes mellitus, primary open angle glaucoma, bilateral cataract surgery and Graves’ disease with subsequent hypothyroidism. In April 2021, he developed vision loss described as complete bilateral, non-simultaneous visual blackout prompted by left/right gaze. His vision returned to baseline on return to centre gaze. There was also a more persistent left visual field defect. Funduscopy identified asymmetric optic disc oedema. The right optic disc showed mild margin blurring with congestion, but with distinct optic disc vessels (Frisén grade 2). The left optic disc had more pronounced optic nerve swelling, indistinct peripapillary arterioles and microhaemorrhages (Frisén grade 3) (figure 1). Ophthalmology, therefore, referred him for emergency evaluation because of concern for permanent vision loss.

1. Is this patient’s vision loss more appropriately classified as transient vascular obscurations or amaurosis fugax?

Transient visual obscurations are caused by episodes of reversible, decreased perfusion to the optic nerve, causing momentary complete vision loss. With binocular vision loss, the localisation can be bilateral in the optic nerves, optic chiasm or retrochiasmal areas. The pathophysiology of amaurosis fugax, a subset of transient visual obscurations, includes hypoperfusion secondary to obstruction or recurrent emboli involving the internal carotid or ophthalmic artery circulation, causing reversible ischaemia to the retina, …