Clinical signs and symptoms

Sudden blindness with persistent loss of visual acuity and visual field is the major symptom of a CRAO. Eye pain is atypical but, when present, suggests occlusion of the ophthalmic artery.

Central retinal artery occlusion is diagnosed ophthalmoscopically. What is seen depends on how soon after the occlusion the examination is made. If the fundus is examined within the first few minutes whilst the occlusion persists, the striking finding is the presence of segmentation of the blood column, boxcar segmentation, with slow "streaming" of flow in the retinal veins. Blood in the arterial branches is dark and a few arterioles may show segmentation (clear areas alternating with areas where the cells appear clumped together), but nowhere is this so obvious as in the veins.

Ophthalmoscopy is rarely performed, however, within the first hour and later inspection of the fundus will show surprisingly little. Typically the disc shows mild pallor and the arteries are only slightly attenuated. Gentle digital pressure on the globe may nevertheless elicit segmentation of the blood column, indicating the presence of a slow but not completely arrested circulation. Total obstruction posterior to the lamina should be suspected when the retinal arteries on the disc start

Figure 12.1 Central retinal artery occlusion with opacification of the retina and a macula cherry-red spot

to pulsate at a touch indicating very low retinal diastolic pressure. With the passage of time, typically after an hour or more, the characteristic fundus changes are seen. The ischaemic retina takes on a white ground glass appearance and the normal red colour of the choroid showing through at the fovea accentuates the central cherry-red spot at the macula (Figure 12.1). Within days of the acute event, the retinal opacification, the cherry-red spot, and the nerve fibre layer disappear and optic atrophy of the primary type develops.

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