2009-11-07 21:23:40 -
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Ocular ischemic syndrome (OIS) is a manifestation of carotid occlusive disease. OIS encompasses the ocular signs and symptoms of chronic vascular insufficiency of the eye. The signs in the anterior segment include uveitis and rubeosis iridis. Posterior segment signs include dot-and-blot retinal hemorrhages, cotton-wool spots, optic nerve and retinal neovascularization (in the late stage), narrowed retinal arteries, and dilated but
nontortuous retinal veins. The most common presenting symptoms are ocular pain and visual loss, either gradual or abrupt. Atherosclerotic disease of the carotid artery is the most common cause. OIS is an infrequent manifestation of carotid occlusive disease. Approximately 5% of patients with marked carotid artery stenosis present with OIS.
Causes of Ischemic Oculopathy
Severe unilateral or bilateral obstruction of the internal carotid artery or marked common carotid obstruction causes OIS. It has been proposed that when the arterial pressure within the eye falls as a result of carotid occlusion, tissue perfusion is not able to satisfy the metabolic needs of the retina. Tissue hypoxia and increasing ocular ischemia are the result of reduction in total ocular blood flow. One of the pathological manifestations of this syndrome is capillary nonperfusion in the peripheral retinal vascular bed. This leads to neovascularization of the optic nerve, iris, and retina.
High-grade carotid stenosis: Stenosis of the carotid artery results in concomitant chronic ophthalmic artery insufficiency. Abnormalities of both anterior and posterior segments of the globe are a result of reduced oxygen delivery to the eye.
Vascular occlusive disease includes occlusive disease of the aortic arch, ophthalmic artery, central retinal artery, and ciliary arteries.
Signs and Symptoms of Ischemic Oculopathy
Ischemic oculopathy produce loss of vision, pain, amaurosis fugax, and afterimages.
Loss of visual acuity is the most frequently encountered symptom, present in more than 90% of affected patients at time of presentation, while 10% of patients had no visual complaints.
Patients with OIS can present with variable visual acuities. About one third of patients present with acuities of 20/20 to 20/40, another one third of patients present with acuities of 20/50 to 20/400. The remaining one third of patients present with acuities of counting fingers to light perception. Visual loss occurs gradually, over a period of weeks to months, but also can occur abruptly.
About 40% of patients with OIS have pain. The pain has been described as a dull ache over the brow, which begins gradually over a period of hours to days. Neovascular glaucoma and ischemia to the eyeball are the possible mechanisms to account for the pain experienced by most patients.
Amaurosis fugax is a transient episode of monocular blindness, or partial blindness, lasting 10 minutes or less. A history of amaurosis fugax is elicited in 9% of patients with OIS.
Afterimages are a prolonged recovery of vision after exposure to bright light.
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