What is retinal angiomatous proliferation (RAP)?
Retinal angiomatous proliferation means there is a growth (proliferation) of abnormal blood vessels (angiomatous) in and under the retina (specifically, under the central part of the retina called the macula). Retinal angiomatous proliferation (RAP) is a sub-type of wet age-related macular degeneration (ARMD). Wet ARMD affects the central vision in older patients due to abnormal blood vessels growing under the macula. The macula is the area of the retina in the back of the eye that is responsible for seeing details in the central vision. The retina is a thin layer of delicate nerve tissue that lines the inside wall of the eye like the film in a camera. In the eye, light is focused through the lens onto the retina, which “takes the picture” and sends the image to the brain.
What causes retinal angiomatous proliferation (RAP)?
Retinal angiomatous proliferation (RAP) appears to be caused by the release of blood vessel growth factors in the retina in response to age-related changes. The age-related changes include the accumulation of cellular waste products under the retina (call subretinal drusenoid deposits). The build-up of waste products (SDD) under the retina interferes with retinal function. For one thing, the build-up of SDD separates the retinal cells from the normal blood vessels that nourish them. Without proper nourishment the retinal cells do not work well. Furthermore, when the retinal cells perceive that they are not getting enough oxygen and nutrients, they release growth factors (including one growth factor called VEGF). These growth factors stimulate the growth of new blood vessels to assist in delivering oxygen and nutrients. In other parts of the body, new blood vessels may grow to help or replace old blood vessels and it is a helpful response to poor blood supply. However, in RAP the new blood vessels cause loss of vision due to fluid leakage, bleeding, and scarring of the macula.
What are the symptoms of retinal angiomatous proliferation (RAP)?
Retinal angiomatous proliferation (RAP) may cause no symptoms in its early stages. Over time, symptoms may include blurred central vision, distortion of straight lines and/or a central, gray spot in the vision. In its advanced stages without treatment, RAP may cause a large permanent blind spot in the center of vision. At this stage no treatment is possible and low vision aids are used to compensate for loss of vision. If one eye develops wet AMD, there is about a 50% chance the other eye will be affected within the next five years.
How is retinal angiomatous proliferation (RAP) diagnosed?
Retinal angiomatous proliferation (RAP) is diagnosed in patients with known dry-type age-related macular degeneration. Before the proliferation or growth of blood vessels under the retina develop in RAP, subtle yellow deposits may be identified under the retina. These deposits are called subretinal drusenoid deposits (SDD). SDD develop many years before RAP occurs. A dilated eye examination can detect SDD and alert the retinal specialist to be on the lookout for RAP. Retinal angiomatous proliferation is suspected when a patient with SDD develops blurred vision and swelling (edema) is present in the retina on a retinal scan called OCT (optical coherence tomography). The diagnosis may be confirmed on a more extensive test called fluorescein angiography. This is a procedure where the ophthalmologist injects an organic dye into the vein of a patient’s arm. Then, photographs of the retina show the presence and location of the leaking blood vessels marked by the organic dye.
Why is this diagnosis important?
It is important to recognize RAP because it guides treatment recommendations. This type of wet ARMD is especially sensitive to antiVEGF therapy (injections with Avastin, Lucentis, and Eylea). RAP is so sensitive to antiVEGF therapy that the medication injections are sometimes not required as often as they are in other types of wet age-related macular degeneration such as PCV. Older treatments such as photocoagulation and photodynamic therapy historically do not work well in RAP and can be avoided. Treatment rarely returns vision to normal, but may limit the amount of vision loss from blood vessel growth and leakage. Frequent office visits and photographs are needed. It may be useful to stop smoking, avoid becoming overweight, exercise daily, and control blood pressure and cholesterol. Aspirin should only be used if required to treat disease as recommended by a doctor. Relatives should be checked for macular degeneration, as well.
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