by Osama Ali

Created on: September 22, 2008

Retinal artery occlusion (RAO) is a potentially devastating visual disorder, usually caused by blockage of a vessel by emboli or atheroma. The emboli, which are visible in 20-40% of eyes, mainly originate in the carotid arteries (74.5%) and are comprised of cholesterol. Fibrin-platelet emboli (15.5%) and calcific emboli from the cardiac valves (10.5%) are also relatively frequent,' whereas emboli caused by corticosteroid use, cardiac myxoma and intravenous drug misuse are uncommon. The site of the pathological process determines whether the central retinal artery (lamina cribrosa), a branch retinal artery or the cilioretinal artery will be affected. Experimental studies have shown that irreversible retinal damage occurs by 24 hrs after central RAO. Numerous treatment approaches have been attempted to improve vision in eyes with RAO, but none has proved particularly effective.

In I990, peyman and Gremillion surgically removed one embolus in a patient with branch RAO of 60 h duration, with a visual acuity improvement to 2/200. The purpose of this study was to assess the anatomical outcome, safety and functional effectiveness of surgical embolus removal in seven consecutive patients with RAO.
Prospective study of seven patients with RAO of < 36 hours duration. All eyes underwent pars plana vitrectomy and a longitudinal incision of the anterior wall of the occluded arteriole in an attempt to remove the embolus. Outcome measures included visual acuity and arteriolar reperfusion, as evaluated with fluorescein angiography.
Surgical removal of the embolus was achieved in six of the seven (87.5%) patients, visual acuity improved from a median of 20/400 (range: hand movements 20/25) to 20/ 40 (range: hand movements 20/25), and reperfusion of the occluded vessel was angiographically confirmed in four of the six patients in whom the embolus was successfully removed.
Cannulation of the CRA is a novel surgical approach that allows direct mechanical access to the site of obstruction. This method presents the advantage of avoiding the risk of neurological complications associated with selective thrombolysis and there is immediate improvement of the blood flow. Immediate improvement of the blood flow leads to the functional improvement of the eye.
Surgical removal of retinal arterial emboli seems to be an effective and safe treatment for RAO, but a randomised and controlled clinical trial will be necessary to establish an evidence base for the role, if any, of this intervention.

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