Age-Related Macular Degeneration

Genetic researchers have been looking for a possible correlation between a genetic mutation and ARMD. They are attempting to distinguish genes that might cause ARMD so that they can develop possible strategies to prevent it. Recently genes that cause Stargardt’s disease, an ailment affecting the retina, have been identified. Researchers decided to see if this same mutation appeared in ARMD patients who had no history of Stargardt’s disease. In 16 percent of the cases it did, which leads them to believe that other mutated forms of the gene may exist. Once these are catalogued, researchers can hopefully begin developing gene therapy procedures. Unfortunately, this will not serve people already affected by ARMD. The use of gene therapy in relation to ARMD will only be available as a preventive measure.

A recent study showed smokers to be approximately 2.5 times more likely to develop ARMD than nonsmokers. Even if a person had quit smoking almost two decades prior there still remained a twofold to threefold increase in the likelihood of developing ARMD. The underlying message is to not pick up the habit in the first place. Exercising preventive measures such as this can increase a person’s chance of avoiding ARMD.

The body naturally produces several byproducts as a result of its metabolic activity. Some of these include molecular oxygen, peroxide, and superoxide, which are collectively referred to as oxidizers because they can readily accept electrons from other molecules. In some cases oxidations are a necessary part of the cellular process and in other instances they are potentially injurious.

To prevent cell damage, the body has a host of molecules called antioxidants, which bind harmlessly to oxidizers, preventing serious harm. With age, it is believed that the body does not produce antioxidants like it once did, leaving it susceptible to oxidative attacks. The eye contains large concentrations of molecular oxygen and it has been theorized that its oxidative qualities are partly at fault for the onset of ARMD. Therefore, doctors have been looking at vitamin therapy (A, C, and E) as a possible treatment or preventive measure because they possess antioxidant behavior. It isn’t known if this is effective in preventing ARMD and caution must be exercised when taking large doses. Too much of anything, even if it is good, has the ability to cause harm.

Zinc is another element found throughout our bodies and is most heavily concentrated in the eye, especially in the retina and macula. It acts as a catalyst in over 100 enzymatic and chemical reactions that are vital to the retina. Like antioxidants, zinc levels appear to decrease gradually with age and many have correlated this with the advancement of ARMD. Consequently, researchers have been experimenting with zinc supplements to discourage ARMD’s progression. Unfortunately, large doses of zinc are extremely damaging to the body and may interfere with the activity of copper (another trace element).

Studies concerning the effectiveness of vitamin and zinc therapies are currently inconclusive. Even if research proves these therapies to be effective in hindering ARMD, caution should be exercised in taking therapeutic doses. However, there are several multiple vitamins commercially available for ARMD patients. Despite this option, everyone should maintain a healthy diet that will adequately and safely provide these essential elements and may help prevent the manifestation of ARMD.

Of all the possible techniques available for treating wet ARMD—generally caused by abnormal blood vessels that leak fluid or blood into the macula—with choroidal neovascularization, laser photocoagulation is probably the most common. A laser is used to cauterize or burn away the developing vascular net. The downside to this treatment is that it leaves a small scar, which results in a blind area. This occurs because laser treatment is not specific to the blood vessels, and also damages the photoreceptors and other cells. However, the scar and loss of vision that result from this treatment may be mild in comparison to what would happen if the vascular network were allowed to advance unchecked. There are several types of lasers that can be used: krypton, argon (an inert gas), and dye. Deciding which one is used is left up to the eye practitioner, but it appears as though krypton and dye lasers are best suited for work near the foveal region of the macula, and that krypton and argon are viable options in treating RPE detachments. Like any medical problem, early diagnosis of wet ARMD is imperative to obtain good results.

Currently under study, photochemical therapy is aimed at contesting the expansion of the vascular network common in cases of wet ARMD. This is accomplished by injecting the cancer drug benzoporphyrin derivative (BPD) into the vessels of the diseased area. The drug is then exposed to laser light, which destroys the cells responsible for vascularization. The most promising aspect is that it supposedly does not affect normal blood vessels in the retinal and choroidal regions, only the damaging vessels. Should this treatment evolve to fruition, it could be the treatment of choice.

Radiation is one of the many types of invasive therapies still in the research phase. The theory behind radiation treatment is that proliferating vascular cells (found in wet ARMD) are highly sensitive to low doses of radiation, whereas healthy retinal and vessel cells are relatively impervious. The treatment is generally given over the course of several days and may affect cells in nearby areas. Early results from many different sites across the country are encouraging, but not definitive.

Strontium 90 is another form of radiation therapy. Instead of applying an external beam of radiation, a small applicator with Strontium 90 is inserted into the eye near the developing vascular network. The benefit of this procedure, as opposed to external beam delivery, is that all the radiation can be delivered at one time instead of over the course of several days. The reason behind this is that the radiation beam has to pass through several layers of the eye and its effectiveness is reduced by the time it reaches the target area. This problem does not arise with the Strontium 90 technique because the radiation is so close to the area in question. Again, additional research must be performed regarding this possibly beneficial technique.

Proton therapy is very similar to radiation therapy in that both use a beam of radiation. The key difference between the two is that in proton therapy the eye is radiated with a proton beam instead of an X-ray beam. This causes less damage to adjacent tissue and initial results show improvement and stability of vision. The drawback to this procedure, should it prove beneficial, is that there are not many proton generators in the U.S. As a result, using one of these generators for eye procedures or even building more would be quite expensive. However, Indiana University is one of the few facilities where proton therapy for ARMD is being studied.

Low vision rehabilitation (LVR) has aided countless ARMD patients. LVR is not a cure for ARMD, but rather a way to help those with retinal damage lead more normal lives. This has been accomplished through a variety of avenues, including special lenses, optical devices, and electronic vision enhancers, to name a few. In addition, ARMD patients have been educated about how to effectively use available vision. Many patients have been told nothing can be done, when in fact low vision aids can be a great help.