Retinal Arterial Occlusion

Retinal Arterial Occlusion

Definition

Retinal infarction due to occlusion of an artery in the lamina cribrosa or a branch retinal artery occlusion.

Epidemiology: 

Retinal artery occlusions occur significantly less often thanvein occlusions.

Etiology: 

Emboli (Table 12.2) arefrequentlythe cause of retinal artery andbranch retinal artery occlusions. Less frequent causes include inflammatory processes such as temporal arteritis (Horton’s arteritis).

Horton’s arteritis should be excluded where retinal artery occlusion is accompanied by headache.

Symptoms: 

Incentral retinal artery occlusion, the patient generally com-

plains of sudden, painless unilateral blindness. In branch retinal artery occlu-sion, the patient will notice a loss of visual acuity or visual field defects.

Diagnostic considerations: 

The diagnosis is made by ophthalmoscopy. Inthe acute stage of central retinal artery occlusion, the retina appears grayishwhite due to edema of the layer of optic nerve fibers and is no longer trans-parent. Only the fovea centralis, which contains no nerve fibers, remains vis-ible as a “cherry red spot” because the red of the choroid shows through at this site (Fig. 12.19a). The column of blood will be seen to be interrupted. Rarely one will observe an embolus. Patients with a cilioretinal artery (artery origi-nating from the ciliary arteries instead of the central retinal artery) will exhibit normal perfusion in the area of vascular supply, and their loss of visual acuity will be less. Atrophy of the optic nerve will develop in the chronic stageof central retinal artery occlusion.

In the acute stage of central retinal artery occlusion, the fovea centralis appears as cherry red spot on ophthalmoscopy. There is not edema of the layer of optic nerve fibers in this area because the fovea contains no nerve fibers.

In branch retinal artery occlusion, a retinal edema will be found in the affected area of vascular supply (Fig. 12.19b). Perimetry (visual field testing) will reveal a total visual field defect in central retinal artery occlusion and a partial defect in branch occlusion.

Differential diagnosis: 

Lipid-storage diseases that can also create a cherryred spot such as Tay-Sachs disease, Niemann-Pick disease, or Gaucher’s dis-ease should be excluded. These diseases can be clearly identified on the basis of their numerous additional symptoms and the fact that they afflict younger patients.

Treatment: 

Emergency treatment is often unsuccessful even when initiatedimmediately. Ocular massage, medications that reduce intraocular pressure, or paracentesis are applied in an attempt to drain the embolus in a peripheral retinal vessel. Calcium antagonists or hemodilution are applied in an attempt to improve vascular supply. Lysis therapy is no longer performed due to the poor prognosis (it is not able to prevent blindness) and the risk to vital tissue involved.

Prophylaxis: 

Excluding or initiating prompt therapy of predisposing under-lying systemic disorders is crucial (see Table 12.2).

Clinical course and prognosis: 

The prognosis is poor becauseirreparabledamage to the inner layers of the retina occurs within one hour. Blindness usu-ally cannot be prevented in central retinal artery occlusion. The prognosis is better where only a branch of the artery is occluded unless a macular branch is affected.