Staphyloma is an abnormal protrusion of the eyeball. The condition may be minor or serious, depending on the severity of the protrusion and its location on the eyeball. In many cases, staphyloma is a resulting condition from severe myopia as the result of severe elongation of the eyeball. In such cases, weakened uveal tissue bulges from the eye by a thinning or weak sclera. There are currently no medical treatments for staphyloma. Many staphyloma cases occur in the back of the eye and go unnoticed until the patient complains of vision loss or a medical exam exposes the condition.
The most common cause of staphyloma is severe, progressive myopia. Also known as near-sightedness, myopia usually results from an abnormally elongated eyeball. The oval shape of the eyeball stretches the vision-producing tissue at the back of the eye, called the retina, and thins the outer protective membrane of the eyeball, called the sclera. The liquid gelatinous material filling the eye, called the vitreous gel, and the uveal tissue supporting the shape of the eye protrude out of place. Other less common causes of staphyloma are trauma, scleritis, glaucoma, infection and inflammation.
In many cases, staphyloma occurs in the posterior, or back side, of the eyeball. Anterior staphyloma occurs within the cornea and is often the result of an eye infection, inflammation or a side effect of eye surgery. In anterior staphyloma, the weak cornea cannot hold the eye contents, and the corneal tissue bulges from the front of the eye. The protrusion appears black or purplish-blue, due to the dark color of the uveal layers of the eye.
Staphyloma is extremely rare amongst African Americans and Caucasians, but occurs predominantly amongst Asians and Middle Easterners. An eye exam may expose the presence of staphyloma, evident from a patient’s axial length of over 1.02 inches (26.5 mm), exophoria in which the eaxis of one eye strays largely away from the axis of the other, and chronic glaucoma. A more definitive dilated fundal eye examination may show posterior atrophy of the eyeball, liquefaction and excessive floaters in the eye’s vitreous gel, cracks or detachments of the retina, and cracks in the inner membrane of the eyeball.
By itself, staphyloma is not harmful or fatal. The condition, however, may damage vision in patients whose vision is already severely compromised with degenerative myopia. Medical professionals currently offer no cure or treatment for staphyloma, but attempt to resolve retinal detachment with laser treatment and myopia with corrective lenses, if possible.