Age-related Macular Degeneration (AMD) is a puzzle whose pieces are interconnected genetic factors, biological processes, age, and environment. Of those puzzle pieces, the only controllable factors are the environmental ones. Twenty-five years ago, ophthalmologists would tell patients that AMD was essentially incurable; eating kale, wearing sunglasses, or quitting smoking might slow the progression of macular degeneration.
Spinach and kale actually are a part of the puzzle. Sunglasses are too. And so is quitting smoking. But researchers also know now how to intervene with biological processes that have gone wrong in the macula. The most obvious example of “gone wrong” is angiogenesis, the formation of new blood vessels. Angiogenesis is a good thing in a developing fetus, or in an adult after a traumatic injury. But when it happens in adults in the choroid layer behind the macula, it causes leakage and permanent damage to the rods and cones of the eye.
Researchers and ophthalmologists now know how to slow angiogenesis (also known as neovascularization) with injections of a drug that suppresses the protein that triggers rogue vessel formation. Those are the very successful AMD drugs called anti-VEGFs. Similarly researchers are investigating the body’s immune and inflammation systems; its cardiovascular systems including the processing of cholesterol; and the various ways cells rebuild themselves and respond to stress from free-radical oxygen. “Biological markers” show that these various biological pathways or systems are all connected with the occurrence of Age-related Macular Degeneration. It’s quite possible scientists will find more ways to stop unhealthy cell processes somewhere in their path.
Meanwhile, genes — the body’s microscopic building instructions, inscribed in every living cell — have become an area of intense interest in the world of AMD and Stargardt Disease research. Geneticists believe we will soon be able to replace genes that trigger disease in the retina with genes that keep cells and biological systems healthy. The genes which are most associated with Age-Related Macular Degeneration include those which encode biological processes in the body: immune and inflammation responses, cardiovascular systems, and cell metabolism pathways. To replace a gene that triggers angiogenesis, or one that lets a healthy cell wall break apart, would be to solve AMD at its source. Gene therapy is of particular interest to people with Stargardt Disease, which is, unlike Age-related Macular Degeneration, triggered by a single cause in most cases, a single gene inherited in a recessive pattern. The possibility of eliminating Stargardt Disease is high, if gene therapy research delivers as much success as it promises.
Some researchers believe we will soon be able to inject laboratory stem cells into the eyes of a person with advanced AMD — eyes in which retinal cells have died off. The stem cells — the anatomical version of a wild card — would do what stem cells do when you put them anywhere in the body. They’d grow into what’s supposed to be there: new cones, rods, and retinal epithelial cells. Finally research is leading to a new technology for people with low-vision from AMD. The artificial retina is a tiny camera and video processor mounted on a pair of glasses, with a sheet of electrodes implanted in the eye. Light signals are collected by the camera and transmitted, by way of the electrodes, to the brain, bypassing the damaged retina. So far the artificial retina allows a pixelated view of outlines of objects. Researchers hope to use the technology to implant the electrodes directly into the brain and restore much of a person’s original vision. So far, the more electrodes, the better the technology works.
The American Macular Degeneration Foundation supports research leading to prevention and a cure for Age-related Macular Degeneration and Stargardt Disease. For a recent example, please see details on the 2013 grant awarded to the laboratory of Dr. Neena Haider at Schepens Eye Research Institute at Massachusetts Eye and Ear Infirmary.