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 than vein occlusions.

Etiology: Emboli (Table 12.2) are frequently the cause of retinal artery and branch retinal artery occlusions. Less frequent causes include inflammatory processes such as temporal arteritis (Horton's arteritis).

12.3 Vascular Disorders 321 Table 12.2 Causes of embolus in retinal artery occlusion

Type of embolus

Source of embolus

Calcium emboli

Cholesterol emboli Thrombocyte-fibrin emboli (gray)

Myxoma emboli

Bacterial or mycotic emboli (Roth spots)

Atheromatous plaques from the carotid artery or heart valves

Atheromatous plaques from the carotid artery

In atrial fibrillation, myocardial infarction, or due to heart surgery

In atrial myxoma (young patients) In endocarditis and septicemia

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

Symptoms: In central retinal artery occlusion, the patient generally complains of sudden, painless unilateral blindness. In branch retinal artery occlusion, the patient will notice a loss of visual acuity or visual field defects.

Diagnostic considerations: The diagnosis is made by ophthalmoscopy. In the acute stage of central retinal artery occlusion, the retina appears grayish white due to edema of the layer of optic nerve fibers and is no longer transparent. Only the fovea centralis, which contains no nerve fibers, remains visible 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 originating 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 stage of central retinal artery occlusion.

H 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 cherry red spot such as Tay-Sachs disease, Niemann-Pick disease, or Gaucher's disease should be excluded. These diseases can be clearly identified on the basis

322 12 Retina Retinal artery occlusion.

322 12 Retina Retinal artery occlusion.

Retinal Image Meaning

Fig. 12.19 a Central retinal artery occlusion. The paper-thin vessels and extensive retinal edema in which the retina loses its transparency are typical signs. Only the fovea is spared, which appears as a cherry red spot.

b Branch retinal artery occlusion. Multiple emboli are visible in the affected arterial branches (arrows).

Fig. 12.19 a Central retinal artery occlusion. The paper-thin vessels and extensive retinal edema in which the retina loses its transparency are typical signs. Only the fovea is spared, which appears as a cherry red spot.

b Branch retinal artery occlusion. Multiple emboli are visible in the affected arterial branches (arrows).

of their numerous additional symptoms and the fact that they afflict younger patients.

Treatment: Emergency treatment is often unsuccessful even when initiated immediately. 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 underlying systemic disorders is crucial (see Table 12.2).

Clinical course and prognosis: The prognosis is poor because irreparable damage to the inner layers of the retina occurs within one hour. Blindness usually 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.

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