Retinal vein occlusion is a common form of retinal vascular disease, especially in middle-aged and older individuals. It occurs when the vein providing outflow of blood from vasculature in the eye becomes blocked.
The retina is nourished and cleansed by a set of tiny blood vessels, the retinal arteries and the retinal veins. Especially in older persons, these fine vessels sometimes become blocked (occluded) with a blood clot (thrombosis) or fatty deposit (embolus).
The symptoms depend on what kind of vessel is blocked. If it is an artery, the retina it supplies stops functioning, causing blindness in part or all of one eye. Unlike retinal detachment, the loss often involves the upper or lower part of the field of vision.
If the blocked vessel is a vein, it may rupture, spilling blood and fluid into the vitreous humor, blurring and clouding vision over a few hours.
Blockage of a retinal artery is an emergency, like retinal detachment. Without a blood supply, the rod and cone cells of the retina will die.
Retinal vein blockage is less frightful. Especially in younger people, the spilled blood may be absorbed. There is no other treatment, although complications, such as overgrowth of new blood vessels, may be halted through coagulation with a laser.
Because blockage of a retinal vein may be undetectable to the victim, regular eye examinations are essential so that treatment of the underlying causes, like high blood pressure, can prevent further damage.
While the initial clinical problems caused by retinal vein occlusion are related to macular changes, other problems may develop.
Branch retinal vein occlusion can result in the proliferation of new vessels on the surface of the retina and the optic disk, which can lead to vitreous hemorrhage and retinal detachment.
In both circumstances, the release of vasoproliferative (reproductive blood vessel) factors by an ischemic retina is thought to be responsible for new vessel formation.
Certain risk factors associated with atherosclerotic disease, such as cigarette smoking and hyperlipidemia (lipids in the circulating blood), also are thought to increase the risk of retinal vein occlusion.
The diagnosis is based on the fundoscopic finding of retinal vein dilation in association with retinal hemorrhages and cotton-wool spots. The pathology can involve the central retinal vein, a branch retinal vein, or a hemicentral vein.
Hemicentral retinal vein occlusion occurs when one-half of a two-trunked central retinal vein becomes occluded in the anterior part of the optic nerve.
Hemicentral occlusion is pathophysiologically similar to central retinal vein occlusion. Retinal vein occlusion can be distinguished clinically from diabetic retinopathy and other retinal diseases.
Treatment of the acute phase of retinal vein thrombosis has included steroids, anticoagulants, streptokinase, aspirin, and plasma expanders. All of these approaches have generally been disappointing. The usefulness of tissue plasminogen activators in the treatment of retinal vein thrombosis is being evaluated.
To prevent neovascularization, retinal photocoagulation (coagulation with laser treatment) is sometimes performed in patients with central retinal vein occlusion and extensive areas of capillary non-perfusion on fluorescein angiography.