There are various retinal artery occlusions that can occur in the eye. Approximately 57% of retinal arterial obstructions involve the central retinal artery, whereas branch retinal arteries account for 38% and cilioretinal artery obstructions represent 5% of the total.
A central retinal artery occlusion is a blockage of the main artery supplying the retina of the eye. It causes severe, sudden, painless loss of vision.
An abnormal pupillary reaction (afferent pupillary defect, APD) can appear within seconds after obstruction of the retinal vascular system. This is typically described as a “cherry-red spot” due to its appearance. In general, the opacification resolves within 4 to 6 weeks, often leaving a pale optic nerve. Acutely, the retinal arteries are usually thinned. In severe cases, segmentation or “boxcarring” of the blood column can be seen in both the retinal arteries and veins.
A branch retinal artery obstruction appears as an area of superficial retinal whitening,most prominent in the posterior pole, along the distribution of the blocked vessel. Regions of more intense whitening are often seen at the boundaries of the ischemic retina.
Well over 90% of branch retinal artery obstructions involve the temporal retinal vessels. It is uncertain whether the temporal arteries are more commonly affected, or if nasal branch artery obstructions are generally asymptomatic.
Cilioretinal arteries usually enter on the temporal aspect of the optic disc, separately from the retinal arterial system.
Cilioretinal artery obstructions appear as areas of superficial retinal whitening along the distribution of these vessels. Three variants can be seen:
- Isolated cilioretinal artery obstruction
- Cilioretinal artery obstruction with central retinal vein obstruction
- Cilioretinal artery obstruction with ischemic optic neuropathy
Approximately 5% of patients with what appears to be a CRAO have, in reality, an acute ophthalmic artery obstruction. In most instances it is difficult to tell whether the ophthalmic artery itself is obstructed or if there are, instead, separate, but simultaneous, obstructions of the retinal and posterior ciliary circulations.
A cherry-red spot may be absent in about 40% of eyes. In the remainder, some degree of a cherry-red spot can be seen. The causes of acute ophthalmic artery obstruction are generally similar to those seen with CRAO.
Systemic workup should include an evaluation for those abnormalities associated with acute CRAO. From there your doctor will recommend a course of ocular therapy.
Unfortunately, a satisfactory treatment regimen for improving vision in eyes with CRAO is lacking. Numerous therapeutic modalities have been attempted, but none has proved particularly effective as of this writing. In addition, since many eyes are given some form of therapy, the natural history concerning vision is not clearly defined.