Macular Degeneration: Cause and Treatment.
Limiting Severe Vision Loss.
Age-related Macular Degeneration (AMD) is the major cause of severe vision loss in people over age 60. While there is currently no cure, the progression of the disease can in some cases be slowed or reversed. You can click on a topic below, or scroll through the entire section.
What is the macula? Located at the back of the eye, the macula is the bull's eye center of the retina. The macula allows us to see fine details such as the numbers on a watch, the features on someone's face, or the amount of spice poured from a container. People with macular degeneration still have peripheral vision, but lose the ability to see the details.
Risk Factors
Risk factors for getting macular degeneration include age (over 50), heredity, smoking, excessive alcohol intake, light skin and blue eyes.
Symptoms
The first sign of macular degeneration may be the appearance of spots, called drusen, in your vision. You may notice some distortion in straight lines. The dotted lines down the center of the road, for instance, may seem crooked or the doorframe may appear warped. If you notice these changes in vision, or if colors look different to each eye, see your eye doctor promptly for an evaluation. Early detection is important for effective treatment.
There are two forms of macular degeneration, "dry" or atrophic, and "wet." Approximately 85-90 percent of people with macular degeneration have the dry form.
Dry AMD
Drusen (spots) on the macula that are present for a long time may cause the macula to thin out and stop working, or atrophy. This is considered the dry form of AMD, and it causes slow, progressive vision loss. There is no medical or surgical treatment for dry AMD, but there are many low-vision tools that can assist with daily living. A research study called AREDS concluded that a specific cocktail of vitamins and minerals could slow the progression of the dry form of AMD and in some cases even reduce it to the wet form . These AREDS-approved supplements are available at most pharmacies. People with dry macular degeneration in one eye may be able to function very well using the central vision from the other eye. Even in cases where dry AMD affects both eyes, there is usually enough peripheral vision to be able to continue activities that don't require fine vision.
The dry form of AMD can change into the wet form, which is much more severe. It is very important that people with dry AMD monitor vision daily with an Amsler grid and report any changes to the eye doctor.
1) This normal view of the Amsler grid shows straight lines
2) For people with macular degeneration, the lines appear distorted
Wet AMD
In the wet form of AMD, abnormal blood vessels grow under the macula and leak fluid and blood. The abnormal vessels, called subretinal neovascularization, may also lift up the retina. In some cases, if diagnosed early enough, an injection in the eye of an anti-vascular endothelial growth factor (ant-VEGF) can seal these vessels and slow vision loss -- or somewhat restore vision. Lucentis (ranibizumab) and Avastin (bevacizumab) have both been used successfully. Newer drugs are always being investigated to improve these positive outcomes even further.
Other Treatments
Some of the descriptions you're about to read may sound highly technical. We encourage you to contact us with questions. We are here to help.
Photodynamic Therapy (PDT)
PDT uses a photosensitizing (activated when exposed to light) drug called Visudyne (verteporfin) that is injected into the patient's arm, and circulates to the abnormal blood vessels. The doctor then focuses an extremely low-energy red laser beam through the pupil of the eye onto the leaky vessels, activating the drug, and destroying the abnormal vessels. The objective is to eliminate abnormal blood vessels while preserving neighboring healthy blood vessels and tissue.
Focal Laser Treatment
This is a dose of higher energy laser treatment delivered to areas afflicted with neovascularization. Focal laser treatment does not improve vision -- it can only stop further deterioration, and it does not work all the time. Successful treatment is often determined by how early the problem is treated and where the abnormal blood vessels are located. In some cases, the abnormal blood vessels will stop growing and leaking for at least one year. But additional abnormal blood vessels will often grow elsewhere in the eye after laser surgery.
Retinal Translocation Surgery
This procedure moves subfoveal neovascular membranes away from the fovea . The goal is to keep the sensory retina working and preserve central vision. RTS has the potential for restoring central visual in some patients with subfoveal neovascular AMD. To date, we have used this technique on three patients . The results: for one patient, we improved the vision from 1/200 to 20/100; a second, from 1/400 to 20/200; and lastly, one patient with 1/400 vision showed no improvement. Complications from the procedure included the development of cataracts in all patients; one patient developed a retinal detachment requiring further surgery. Patients who have vascularized pigment epithelial detachment or subretinal fibrosis from AMD should not undergo this procedure.
External Beam Irradiation for Macular Degeneration
EBI is a proven treatment of hemangiomas (rare, benign tumors of the eye). It is also used to cause regression of abnormal blood vessels, resulting in the reabsorption of fluid and blood. Our experience using EBI suggests that low-dose radiotherapy (up to 2500 rads) is an effective to treat subretinal neovascularization without destroying the overlying retina.
Gene Transfer
Biochemical mediators are being developed in major research and development programs. This important class of therapeutic agents is a result of advances in genetic engineering and biotechnology. In this treatment, therapeutic genes are delivered to target tissue by removing cells from the patient, placing the desired gene into these cells, and them to the treatment area. These therapeutic genes will create healing factors such as killing abnormal cells (like endothelial cells) that are causing the loss of vision; and to encourage the proliferation of cells to replace damaged cells such as photoreceptor cells within the retina.
The main challenge of gene transfer is delivering the therapeutic gene to the patient's target tissue. We are currently able to modify a certain virus and implant a desired therapeautic gene for viral replication. This genetically altered virus then transfers the desired therapeutic genes to target tissues for the destruction of abnormal cells or the production of new cells. At present, the biggest challenge is developing and altering these viruses so their ability to deposit their genes into the target cells is controlled. In the future, researchers will be able to choose one or a variety of gene delivery systems for target tissues. This type of research offers the most promise for the long term treatment of conditions, such as AMD.
Click Here to find out about our New England Retina Research and Education Foundation
Click Here to link to The Foundation Fighting Blindness
