Causes

No one knows the exact cause of wet macular degeneration, but it develops in people who have had dry macular degeneration. Of all people with age-related macular degeneration, about 20% have the wet form.

Wet macular degeneration can develop in different ways:

• Vision loss caused by abnormal blood vessel growth. Sometimes abnormal new blood vessels grow from the choroid under and into the macula (choroidal neovascularization). The choroid is the layer of blood vessels between the retina and the outer, firm coat of the eye (sclera). These abnormal blood vessels may leak fluid or blood, interfering with the retina's function.
• Vision loss caused by fluid buildup in the back of the eye. When fluid leaks from the choroid, it can collect between the thin cell layer called the retinal pigment epithelium and the retina or within the layers of the retina. This may cause a bump in the macula, resulting in vision loss or distortion.