American Medical Association Family Medical Guide - American Medical Association [745]
Symptoms
If the central retinal artery becomes blocked, the result is immediate blindness in the affected eye. If a branch of the artery is blocked, part of the visual field in the affected eye—usually the upper half or the lower half—is blacked out. If you suddenly lose all or part of your vision in one eye, see an ophthalmologist immediately or go directly to the nearest hospital emergency department.
Diagnosis and Treatment
A diagnosis of retinal artery occlusion is based on the symptoms and an examination of the affected eye. In rare cases, it may be possible to restore some of the lost vision by causing the clot or embolus to move farther along the blood vessel to a position where less of the retina is affected. This may be done by reducing pressure inside the eye, either with medication or by draining excess fluid, within a few hours of the appearance of symptoms.
Retinal Vein Occlusion
The central retinal vein carries oxygen-depleted blood away from the retina (the light-sensitive membrane lining the back of the eye). In rare cases, usually in middle-aged or older people, the central retinal vein or one of its branches becomes blocked by a thrombus (blood clot), which causes blood to leak from the blocked vessel, blurring vision.
Retinal vein occlusion may occur in chronic glaucoma (see page 1042) or with high blood pressure (see page 574). In rare cases, the disorder results from blood diseases in which the blood is thicker than normal and tends to clot more easily. Effective treatment of an underlying disease or condition, such as high blood pressure, can help prevent retinal vein occlusion.
Symptoms
If the central retinal vein becomes blocked, it usually causes sudden blurring of vision in the affected eye. When retinal artery occlusion (see previous page) occurs along with retinal vein occlusion, any blurring of vision is usually worse and more likely to be permanent. When retinal vein occlusion occurs alone, vision may improve as the clot is reabsorbed. However, permanent damage to the vein or retina frequently occurs.
Diagnosis and Treatment
A diagnosis of retinal vein occlusion is based on the symptoms and an examination of the affected eye. Sometimes retinal vein occlusion is detected by chance when an ophthalmologist examines the inside of the eyeball with an ophthalmoscope (a viewing instrument that projects a bright light onto the back of the eye) during a routine eye examination. In some cases, an ophthalmologist may recommend laser surgery (which uses a highly concentrated beam of light) to help close leaking blood vessels.
Choroiditis
Choroiditis is inflammation of the choroid, the layer of blood vessels beneath the retina (the light-sensitive membrane lining the back of the eye) that supplies the eye with oxygen and nutrients. In some cases, the retina and the vitreous fluid (the substance that makes up the mass of the inside of the eyeball) also become inflamed. Although the exact cause of the disorder usually cannot be identified, sometimes an infectious agent such as the bacterium that causes tuberculosis (see page 663) is the cause. In some cases, an abnormal immune response mistakenly produces antibodies (infection-fighting proteins) that attack the choroid and sometimes other parts of the eye.
Symptoms and Diagnosis
The symptoms of choroiditis include redness, discomfort, and blurred vision in the affected eye.
A diagnosis of choroiditis is based on the symptoms and an eye examination. An ophthalmologist will probably order blood tests to check for an infection, and possibly an ultrasound (see page 111) if he or she cannot see far enough into the eyeball with an ophthalmoscope (a viewing instrument that projects