CENTRAL RETINAL ARTERY OCCLUSION
Posted by recep on April 14th, 2009Occlusion of the central retinal artery produces sudden blindness in the affected eye. The typical cause in older patients is an atheroma, usually broken off the carotid artery wall. The atheroma occludes the central retinal artery in the deeper portion of the optic nerve head and thus cannot be seen. Within an hour after loss of vision, the arterial spasm ceases, and some blood flow is restored to the retina, giving the appearance of a relatively normal retina on ophthalmoscopy. However, within several hours, the retina becomes edematous and gray from the death of retinal ganglion cells. Because the retina in the foveal area contains no ganglion cells, the reddish underlying choroid remains visible, accounting for the characteristic central cherry-red spot surrounded by gray retina. In 2 to 3 wk, the cherry-red spot disappears, and as the ganglion cells and their axons die, the optic nerve becomes white, the hallmark of primary optic atrophy.
When an atheroma breaks off, passes through the central retinal artery, and lodges in a retinal artery branch, it can usually be seen as a retractile object in the branch and is referred to as a Hollenhorst plaque. This finding indicates embolic activity, usually from the carotid system. The portion of the retina supplied by the occluded vessel loses its function and a visual field defect, which may not affect central vision, results.
Intervention is needed within a few minutes of the occlusion to prevent retinal cell death. Acutely reducing intraocular pressure by paracentesis combined with vasodilators may occasionally prevent this complication.
