WHAT IS MACULAR DEGENERATION
AND ITS TREATMENT OPTIONS?
What Is Macular Degeneration?
Age-related macular degeneration (ARMD) is the most common cause of irreversible vision loss in Americans over the age of 60. It is estimated that 10 million Americans will experience this age-related visual impairment during their retirement years.
Macular degeneration is a disorder of the retina, the light-sensitive inner lining of the back of the eye. The macula is a small, central portion of the retina which is necessary for sharp, “straight ahead” vision needed for reading, driving a car or recognizing faces.
There are a number of abnormalities associated with the term “age-related macular degeneration.” They range from mild changes with no decrease in vision to abnormalities severe enough to result in the loss of all “straight ahead” vision. Macular degeneration does not cause total blindness because the remaining and undamaged parts of the retina around the macula continue to provide “side” vision.
There are two main types of macular degeneration, “dry” and “wet,” both are discussed in the next section.
Signs and Symptoms
Aging causes the cells in the retina to become less efficient. Ultimately, deposits called drusen appear under the retina and can be seen during an eye examination and on photographs of the retina . A few small drusen may cause no decrease in vision (photo 1). However, if too many large drusen develop, vision will decrease (photo 2). Vision may also be affected when there are disturbances in the layer of cells below the retina called the retinal pigment epithelium. These two types of changes are known as “dry” and “wet” macular degeneration. Dry is the most common form and currently, there are no known treatments for dry AMD.
TREATMENT OPTIONS OF ARMD
A few people experience the “wet ARMD” form of macular degeneration which can cause more severe visual loss (see wet ARMD photo). In this situation, abnormal blood vessels grow beneath the retina and result in bleeding and leakage of fluid. Vision may suddenly become distorted or blurred. In some cases of wet macular degeneration, laser treatment can be effective at destroying the abnormal vessels, thus preventing or slowing further visual loss. Wet macular degeneration cannot always be treated successfully by laser, however, some experimental drugs and new surgical procedures (photodynamic therapy) are being tested.
- Laser Photocoagulation
- DRUG THERAPY’S In the search for better methods to combat wet age-related macular degeneration, drug therapy is emerging as one of the most promising weapons of choice.
- ANTI-VEGF Abnormal blood vessel growth (neovascularization) is set off by a complex series of interactions in the cell. A protein molecule called vascular endothelial growth factor (VEGF), signals cells to produce these misguided vessels. Most of the drugs being developed for wet AMD are designed to target VEGF one way or another to inhibit this unwanted blood vessel growth and reduce leakage and bleeding.
- MACUGEN (pegaptanib) This is the first anti-VEGF ophthalmic drug approved by the Food and Drug Administration, Macugen became available in clinical practices last January. It is delivered by injection to reach the back of the eye. Patients typically receive injections every sex weeks for two years and show minimal side effects. Phase III clinical trials of Macugen have found that treated patients has a 27% greater chance of avoiding moderate visual loss.
- LUCENTIS (ranibizumab) This VEGF antibody is on the final phase of clinical trials and may receive FDA approval in 2006. One year results from two studies on Lucentis were very encouraging. The substance is a modified version of the drug Avastin (see below), which is used to treat colorectal cancer. It also is injected directly into the eye every four weeks.In mid-July 2005, Genentech officials reported that Lucentis potentially could improve vision in a significant number of macular degeneration patients who already have experienced vision loss from the “wet” form of the disease.This data is very compelling because, for the first time, there is a potential treatment which has been shown to improve vision in a significant number of patients with wet AMD as opposed to just slowing progression of vision loss.
- AVASTIN (bevacizumab) This drug, from which Lucentis is derived, is being explored as a therapy for wet AMD. Early study results of Avastin, which is injected directly in the eye, have been encouraging. In addition, the cost of this treatment is significantly less than the other anti-VEGF drugs. However further studies are needed to determine its safety and effectiveness.
- EVIZON (squalamine lactate) Evizon is the first clinical drug candidate in a class of naturally occurring molecules know as aminosterols. It is a potent molecule that blocks the action of a number of angiogenic growth factors, including VEGF. The drug, which is given by intravenous infusion, has been tested for several types of cancers, in addition to wet AMD. Phase II trials of Evison for AMD showed positive results, with the patients experiencing stable or improved vision.
- ANTI-ANGIOGENIC AGENTS
- KENALOG (triamcinolone acetate) This anti-inflammatory drug is being used to minimize blood vessel growth. It is being studied in conjunction with photodynamic therapy (PDT) to reduced the persistence or growth of abnormal blood vessels.
- RETAANE (acecortave acetate) This steroid compound, delivered behind the eye using a blunt-tipped, curved tool, continues to be studied. Treatments are spaced about six months apart.
- Photodynamic therapy (PDT) with Visudyne
- Vitamins and Supplements For ARMD
- Transpupillary Thermotherapy (TTT) Photocoagulation
- Sub Macular Surgery with Tissue Plasminogen Activator (TPA)
- Macular Translocation
- Retinal Implant or Transplant
- Regeneration of Retinal Cells
A Self Test for ARMD
The Amsler Grid (see figure below, for a further explanation and printed copy, see the Amsler Gridpage) is used to screen for macular degeneration. In an effort to detect loss of vision associated with macular degeneration, eye care providers across the country are recommending this test to their patients. The test involves looking at a square grid with a dot in the center. The grid should be held 12 inches away from the face. While wearing eye glasses normally worn when reading, the individual covers one eye at a time. With the uncovered eye, the individual stares at the dot in the center of the grid. All four corners of the grid should be visible, and the lines of the grid should appear to be straight and continuous from top to bottom and side to side. If there appear to be any holes or blurry spots, or the lines look wavy, fuzzy, crooked, distorted or broken, the individual should call their eye doctor immediately.
Click if you would like to see a printable Amsler Grid page with instructions.
Today’s advances in medicine means that more and more older Americans will be able to maintain good vision as they age. Since many serious eye conditions are treatable when detected at an early age, it is important to have periodic eye examinations from an eye care provider, especially as one approaches the sixth decade of life.