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Wet (Exudative) Macular Degeneration
For reasons that are not fully understood, a minority of people with macular degeneration develop a more serious form of the disease. People with large “soft” drusen (drusen with indistinct borders), many drusen that run together, or focal pigmentation are at greater risk for developing the wet (exudative) form of the disease.
In the wet form of macular degeneration, new blood vessels begin to grow underneath the retina. The proliferation of these new blood vessels is called choroidal neovascularization, or CNV.
In a variant form of the disease, the new blood vessels may begin within the retina and grow toward the choroid layer. This form is called retinal angiomatous proliferation, or RAP. Another variant is called polypoidal choroidal vasculopathy, or “polypoidal.” The polypoidal vessels in this condition tend to cause extensive bleeding under the retina.
In wet macular degeneration, new blood vessels grow underneath the retina in a process called choroidal neovascularization, or CNV. (Click image for full size image.)
It is believed that the diseased retina stimulates the production of these new blood vessels in response to a decreased supply of nutrients and slow transport of wastes. Unfortunately, new blood vessels do not improve the health of the retina. Instead, they often leak blood or fluid into the retina.
This retinal photograph shows fluid and blood beneath the retina which suggests the presence of choroidal neovascularization (CNV). (Click image for full size image.)
As CNV continues, the new vessels may leak blood or fluid under the retina, causing the retinal surface to become uneven. As a result, objects in that portion of your visual field may appear wavy or distorted. The neovascularization may even break through some of the retinal layers. Blind spots may appear in your vision if portions of the retina become damaged by the CNV.
Often the first sign of fluid under the retina is distortion of straight lines. Just as in a camera, if the film is not lying flat, images will be distorted. Since these changes can be subtle, regular testing with the Amsler grid in this booklet can be helpful in the early detection of problems.
As the surface of the retina becomes uneven, objects in your vision may appear blurred, wavy, or distorted. As the condition progresses, blind spots may appear.
Any change in the appearance of the grid may be a sign of choroidal neovascularization and should prompt a visit to the eye doctor. If caught early enough, the CNV might be treatable before it causes too much damage.
The first indication of fluid under the retina may be a distortion of straight lines. The Amsler grid test is an important tool for the early detection of any changes in your vision.
Eventually, areas of neovascularization and leakage can lead to the death of the overlying photoreceptors and scarring of the macula. Scarring is the final stage of macular degeneration, and it frequently results in significant visual loss.
It is important to realize that this entire process occurs only in the macula, and affects only central, or detail vision. Peripheral, or side vision is rarely affected by macular degeneration. While macular degeneration is the leading cause of legal blindness, it rarely leads to total blindness.
Legal blindness means the vision is 20/200 or worse in the better eye even with corrective lenses or that the peripheral visual field is restricted sufficiently to cause tunnel vision.
This retinal photograph shows a large yellow scar in the macular region resulting from advanced CNV. A person with this type of scarring would experience a significant loss of vision in that eye. (Click image for full size image.)