Central Retinal Vein Occlusion with Cilioretinal Arteriolar Insufficiency and Perivenous Superficial White Patches

This 63 year old man with hypertension and hypercholesterolemia awoke with painless visual loss of the left eye secondary to a central retinal vein occlusion. The white band of retina extending from the optic disc toward the macula is ischemic retinal whitening in the distribution of a cilioretinal artery (note the branches marked with yellow arrows). There is no physical obstruction of this cilioretinal arteriole - no clot or embolus is present. Instead, the high venous pressure caused by the CRVO has hemodynamically reduced blood flow through this cilioretinal arteriole to the point that retinal transparency has been impaired (a trait that requires high oxygen tension). This did not happen in the other zones of the macula because the perfusion pressure of the central retinal artery is slightly higher than the perfusion pressure in the ciliretinal artery, which is a branch of the posterior ciliary arteries, not a branch of the central retinal artery. The perivascular white patches (black arrows) resemble cotton wool spots, but their perivenous arrangement suggests a different pathogenesis than an arteriolar infarct, the usual explanation for a cotton wool spot. McLeod's explanation of these being sentinels of local ischemia causing axoplasmic flow stasis makes the most sense.