AMD: Age-Related Macular Degeneration
Macular Degeneration Videos
Even in covering the highlights of Macular Degeneration there is too much material for a ten minute video, so I have divided the subject into two parts, and it is still only highlights.
The first video describes the biology of the aging retina and how that evolves into Macular Degeneration.
The second discusses prevention and treatment. Prevention in terms of results from the Age Related Eye Disease Study, using antioxidant vitamins and zinc. Treatment was previously by laser, but now is mostly by the VEGF inhibitors Lucentis and Avastin.
The biggest unsolved problem in ophthalmology is macular degeneration. In general terms it is deterioration, related to aging, of the center part of the retina. Thus it reduces the part of vision that allows you to see detail, like read a book and recognize people. The peripheral retina is not affected so side vision is not lost.
Macular Degeneration: Dry vs. Wet
Macular Degeneration comes in two types, dry and wet.
To visualize the affect of the aging process on the retina picture the retina as two layers. On top is a layer of nerve tissue, with the rods and cones that sense light and the nerve fibers to carry that information to the brain. Beneath the nerve layer is a layer of pigmented cells (Retinal Pigment Epithelium, RPE) which is important because it supports the metabolism of the nerve layer. The photoreceptors are constantly shedding parts that are digested by the pigment cells. Over a lifetime of digestion waste material begins to build up within the pigment cells. Beneath the retina is a layer of blood vessels (Choroid) that supplies oxygen and nutrients to the outer retina.
The first stage of macular degeneration involves the accumulation of waste material in the pigment layer that appears as little white spots, called drusen. As the spots get bigger and denser vision usually starts to degrade. The other common appearance relates to loss of the pigment cells, called atrophy. That appears as pale patches that may be of any size or shape.
Progress of the “dry” form usually takes a very slow and protracted time course.
Macular Degeneration. Moderate. Dry.
The yellow spots, called “drusen,” are the accumulation of waste material in the pigment layer under the retina.
Macular Degeneration. Moderate “soft” drusen. Dry.
Macular Degeneration. “Atrophic” form.
Instead of waste deposits accumulating in the pigment layer as drusen, the pigment layer simply wastes away. Still dry.
Macular Degeneration. “Wet” Form. The hemorrhage seen here is under the retina.
As the dry form advances the chance of developing leakage from underlying blood vessels increases. The development of leakage represents a dramatic change in the course of events leading to a large and rapid loss of central vision unless there is prompt intervention.
If the leakage can be caught in the early stages there is the potential to treat it with laser or a new injected medication. The laser has been available for several decades to accomplish a variety of things that were previously difficult to do, or couldn’t be done. In this case it is used to cauterize the leaking vessels. That results in damage to a smaller area of retina in order to save vision in a larger area.
The new injected medication (Lucentis or Avastin) aims to make the leaking vessels regress without damaging any retina. It does that by blocking the action of VEGF (Vascular Endothelial Growth Factor), the chemical signal that stimulated the vessel growth to begin with. These medications have been successful beyond initial expectations and are fast becoming the mainstay of treatment in this and other related retinal diseases. Since it is new there are still protocols to be worked out, like how often it must be administered, and for how long.
The landmark Age-Related Eye Disease Study showed us that the progress of macular degeneration may be slowed somewhat by taking a nutritional supplement containing antioxidant vitamins and the mineral zinc. A report on the ten year data are shown in that section.
Because early detection of change from dry to wet AMD is the key determining factor in visual outcome it is important for people with macular degeneration to monitor their vision on a regular basis.
Vision monitoring can be done with the Amsler grid (looks like a small page of graph paper) or simply with a page of print. Test each eye by itself. Cover one eye and look for an increase in distortion or missing areas. The first time you do this will be considered as a baseline. Then check at least weekly for changes from that baseline.
If you have macular degeneration and you notice a progressive change in vision you should contact your ophthalmologist promptly.