Age Related Macular Degeneration
How the Eye Sees
Light rays enter the eye through the cornea, pupil, and lens. These light rays are focused on the retina, a light-sensitive tissue lining the back of the eye. The retina has two areas: the peripheral retina, and the macula. The macula is a small area at the center of the retina. The peripheral retina is the large area surrounding the macula. It is the peripheral retina that gives us our “side” or “wide-angle” vision. It is the macula that gives us our “pinpoint” vision and allows us to see details clearly, helping us to do things like drive, read, or recognize a face. Age-Related Macular Degeneration, or AMD, is the breakdown of the macula. When the macula doesn’t work properly, your central vision can be affected by blurriness, dark areas, or distortion. This condition affects many people as they get older.
The retina is made up of many layers that are sandwiched together into a smooth surface. These layers work together, allowing us to see clearly. In people with Dry AMD, the layer under the retina, known as the retinal pigment epithelium, (or RPE,) is affected by deposits, (called drusen,) as well as other age-related changes. These changes may cause vision to deteriorate.
A basic, yet important, tool for monitoring your vision is called an Amsler grid. You can use it at home to detect changes in your central or macular field of vision. You simply sit in a well-lit area and hold the grid away from you at a comfortable position. If you wear glasses, you should keep them on. Cover one eye and look directly at the point at the center of the grid, but observe the pattern of vertical and horizontal lines in your peripheral vision. Then, do the same with the other eye. Typically, a visual abnormality due to AMD would cause some of the straight lines to appear wavy or blurry, or areas to appear dark or even blank. If you notice any new changes in the grid, you should contact your ophthalmologist immediately.
With Wet AMD, abnormal blood vessels begin to grow under the retinal layers behind the macula. These blood vessels leak fluid, or bleed, which further blurs or distorts central vision. About ten percent of people with macular degeneration have the wet form.
Fluorescein dye is injected into a vein in your arm, and the dye travels to the blood vessels in the eye. A special camera is used to photograph the retina and blood vessels, which are illuminated with dye. These images provide a map of problem areas, and help your doctor identify appropriate treatment options, and monitor their effectiveness.
Laser for Wet AMD
With laser therapy for wet AMD, the pupil is dilated using drops and an anesthetic is given to numb the surface of the eye, and, in some cases, to keep the eye from moving. A special contact lens is placed on the surface of the eye to help the surgeon see the retina. A high-energy laser beam is aimed at the tiny leaking blood vessels, to seal them, and to help stop them from growing. It is important to stop the spread of these vessels as quickly as possible, but depending on how close they are to the center of the macula, the patient may experience some further permanent blurring or loss of vision after the procedure. Of the patients with Wet AMD who have the standard laser procedure, it is likely that fifty percent of them will need a re-treatment within three to five years.
The anti-VEGF drug is administered directly into the eye in an outpatient procedure. After the eye has been numbed with an anaesthetic, the anti-VEGF drug is injected into the eye with a very fine needle.
This procedure uses a combination of a light-activated drug and a special low power or “cool” laser. The photo-sensitive drug is injected into the patient through an intravenous infusion and travels to the [00:00:14 abnormal] vessels behind the central macula. The drug attaches to molecules that are commonly found in rapidly growing cells, such as those in Wet AMD blood vessels. A low powered laser light is focused directly on the [abnormal] vessels, which actives the drug, causes damage specifically to the unwanted blood vessels. Usually, multiple treatments are required.