What is Macular Degeneration?
Updated: Dec 6, 2022
The Warning Signs & Symptoms of Macular Degeneration: When is it time to talk to your doctor?
Age-related macular degenerative disease (AMD) is a progressive disorder that affects the macula, the area of the retina responsible for fine detail vision. It occurs when the light-sensitive cells in your eyes stop working properly. This is the most common type of AMD, accounting for about 90% of cases and affecting about 10 million Americans.
AMD is the leading cause of blindness among Americans aged 50 and older.
The macula is located just behind the center of the retina, where light enters the eye and is focused onto the photoreceptors. These are cells in the retina that convert light into electrical impulses that are sent to the brain via the optic nerve.
How Your Eyes See
When you look at something, light hits your eyes and passes through the cornea and lens. The iris adjusts the amount of light entering the eye by changing the size of the pupil. Light then travels through the vitreous humor, a clear gel-like substance that fills the space inside the eyeball, to reach the retina.
The retina contains millions of tiny rods and cones, specialized light receptors that detect different wavelengths of light. When light strikes the retina, the rods react quickly, sending signals along the optic nerve to the brain. Cones take longer to respond, but they provide color information.
The macula contains many cone cells, which allows us to distinguish colors and recognize objects such as letters and numbers. In addition, the macula contains high concentrations of rod cells, which allow us to see well even in dim conditions.
In healthy individuals, the macula receives enough blood flow to function normally. However, in patients with AMD, there is often insufficient blood supply to the macula, causing abnormal changes in the retinal pigment epithelium (RPE) cells. RPE cells are essential for maintaining normal vision because they produce substances called growth factors that help support the health of the underlying photoreceptor cells.
As the RPE cells deteriorate, they lose their ability to nourish the photoreceptor cells. As a result, the photoreceptor cells die, resulting in permanent vision loss.
What are the types and stages of AMD?
There are two types of AMD: dry AMD and wet AMD.
Dry AMD is characterized by drusen, which are yellow deposits under the retina.
Wet AMD is characterized by choroidal neovascularization (CNV), where abnormal blood vessels grow beneath the retina.
Some people develop dry AMD, while others develop wet AMD. Dry AMD often starts out as early AMD, and wet AMD begins as intermediate AMD.
The three stages of AMD are:
Early AMD, characterized by small white spots or flecks near the center of your field of vision. Early AMD usually doesn't cause symptoms, but it does increase your risk of developing advanced AMD.
Intermediate AMD, characterized by larger areas of white spots or flecks.
Advanced AMD, characterized by large areas of white spots or patches. This stage can causes problems like blurry vision, blind spots, and even total vision loss.
Prevention and Treatment of AMD
The good news is that there are preventions and certain treatments for both kinds of AMD. You can treat dry AMD with laser therapy, injections, or surgery. For neovascular AMD, doctors use anti-VEGF drugs such as Lucentis and Avastin.
Preventive measures for dry AMD include:
eating foods rich in antioxidants like blueberries, carrots, spinach, broccoli, tomatoes, and dark green leafy vegetables;
getting regular exercise;
limiting alcohol consumption;
and wearing sunglasses to protect your eyes from UV rays.
Early AMD isn't treatable, but there are ways to manage it including diet and exercise. Talk to your eye doctor about what you can do to prevent it from progressing to later stages.
Late AMD is treatable. Special dietary supplements called antioxidants may slow the progression of AMD in your other eye, and laser therapy may improve vision in some cases.
Wet AMD requires immediate medical attention. Your doctor may recommend surgery to drain fluid from your retina. This is known as intravitreal injections. Other treatments include medications and photodynamic therapy.