Central retinal artery occlusion (CRAO) results most commonly due to embolism or intravascular thrombosis causing sudden, painless, monocular visual loss as a result of loss of blood supply to the inner retinal layers.

Acute CRAO is one of the major causes of acute visual loss with incidence estimated to be 1 to 10 in 100,000.¹

About 15% to 30% of the population have a cilioretinal artery that may provide additional blood supply to the fovea which may preserve central vision.²

Classic ischemic fundus findings include cotton wool spots (CWSs), retinal whitening, “cherry-red spot,” foveola, and “box-carring” appearance (ie, segmentation of blood in retinal vessels).

Fluorescein angiography (FA) shows clear retinal vascular delay and capillary nonperfusion.

Optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) are useful to evaluate the presence and extent of retinal nonperfusion, increased inner retinal reflectivity, and areas of atrophy and to visualize changes in the capillary network.

Reperfused CRAO may occur with transient symptoms and minimal signs on examination. Residual findings may be noted on OCT and/or OCTA during both the acute and chronic phase.

Acute CRAO is characterized on OCT by increased reflectivity and thickness of the inner retina due to ischemia, corresponding with retinal whitening and cotton wool spots on biomicroscopy. Increased reflectivity results in shadowing for outer structures. This hyperreflectivity crosses retinal layers often resulting in loss of the retinal laminar appearance (Figure 10.1).³

A hyperreflective band at the level of the inner nuclear layer (INL) may be present, also termed paracentral acute middle maculopathy (PAMM), which represents ischemia of the intermediate and deep retinal capillary plexuses. This may also be present in eyes with reperfused CRAO (Figure 10.2).⁴

Thickness of the inner retina layer decreases in the middle period of the retinal artery occlusion, but the hyperreflective band remains and helps for the diagnosis.