retinal arterial occlusion
Occlusion of the central retinal artery (CRAO) is characterized by a sudden loss of vision and a defective direct pupil light reflex. The retinal arterioles are constricted while the veins are full but a venous pulse is absent. The retina appears white and swollen, especially near the posterior pole, and the choroid is seen through it as a cherry-red spot (Fig. S12). If the occlusion persists the cherry-red spot disappears after several weeks, the retinal arterioles remain attenuated, eventually becoming white threads, and the optic disc becomes atrophic.Occlusion is more frequently limited to one branch of the central retinal artery (BRAO). In this case, the clinical picture is limited to the area supplied by the branch and this is associated with a visual field defect in that region. Causes include retinal emboli due to a cardiovascular disease, systemic hypertension, temporal arteritis, oral contraceptives, syphilis, intravenous drug abuse or trauma. Treatment is urgent as there is an extremely serious risk of blindness. See amaurosis fugax; fluorescein angiography; atheroma; Hollenhorst's plaques; cherry-red spot.
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Fig. S12 Cherry-red spot at the macula
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