Myopia, or nearsightedness, is a common eye condition. More than 40% of Americans can't see clearly at a distance because their eye is longer than normal. Usually myopia doesn't cause any problems other than the need for glasses or contact lenses.
A small number of people have a more severe form of nearsightedness called high myopia. The light-sensitive layer called the retina in
the back of their eye stretches. The retina can stretch so much that the eye becomes damaged. Pathological myopia is the name for eye diseases caused by myopia.
Myopic macular degeneration happens when the macula, the part of the retina that helps you see clearly straight ahead, becomes so damaged that you lose vision. It's like age-related macular degeneration (AMD), except that it affects younger people.
Regular eye exams are important when you have myopia. Your eye doctor can find and treat problems before they cause vision loss.
Causes of Myopic Macular Degeneration
Normally, your cornea and lens bend light that enters your eye so that it lands right on your retina. The retina is the thin layer in the back of your eye that converts light into images and sends them to your brain. The macula is part of the retina.
In myopia, your eyeball is longer than normal. It aims light in front of your retina instead of on it. That's why you have more trouble seeing objects in the distance.
The longer eyeball makes the white part of your eye (sclera) and retina stretch. It's like stretching a balloon. The retina can become so thin that it tears. Cells in the macula can die and form a blind spot in the center of your vision. Damage to the macula is called macular degeneration.
About 1 in 10 people with severe myopia get the wet form of myopic macular degeneration. It's similar to wet AMD. Abnormal blood vessels grow underneath the macula and leak blood, which leads to vision loss.
Symptoms of Myopic Macular Degeneration
You might not have any symptoms in the early stages of the disease. Once the macula becomes very damaged, symptoms can include:
- Blurring in parts of your vision
- Straight lines that look wavy
- A blind spot in the middle of your vision
Who Is at Risk?
Myopic macular degeneration affects people with severe myopia, which is an eyeglass prescription of -6 diopters or more. The risk is even greater for prescriptions of -10 diopters or more. Diopter measures the correcting power of your lens. A negative number means you are nearsighted. The higher the number, the more nearsighted you are.
Certain genes might increase the risk for this condition. We don't know yet which genes are involved, but myopic macular degeneration seems to run in families. Women and people of Asian descent also may be at higher risk.
How Is Myopic Macular Degeneration Diagnosed?
An eye doctor can diagnose myopic macular degeneration during a routine exam. It's important for anyone with high myopia to get regular vision checks starting in childhood.
Your eye doctor may do one or more of these tests:
Vision test. You read letters on an eye chart to measure the sharpness of your vision. Severe nearsightedness is a sign of myopic macular degeneration.
Dilated eye exam. Your eye doctor uses eye drops to widen your pupil and check the retina and other structures in the back of your eye. Damage to the retina and new abnormal blood vessels are signs of myopic macular degeneration.
Visual field test. This test measures your side vision.
Amsler grid. This grid has straight lines that look wavy when you have macular degeneration.
Fluorescein angiography (FA). Your eye doctor uses a special camera to take pictures of your retina. This test can show leaky blood vessels in your macula.
If you have macular degeneration, you can use an Amsler grid at home between eye doctor visits to see if your vision has changed. You cover one eye and stare at the grid with the other. Wavy or blurred lines on the grid could be a sign of leaky blood vessels and a reason to call your eye doctor.
How Is Myopic Macular Degeneration Treated?
If you have high myopia, your eye doctor can check you for macular degeneration during exams. You can wear glasses or contact lenses to correct vision loss.
Treatment for myopic macular degeneration is the same as for wet AMD, with injections of anti-VEGF medications or ANG2. These medicines stop new blood vessels by blocking pathways the vessels need to grow. Ranibizumab (Lucentis) is the anti-VEGF medication that's approved for myopic macular degeneration.
Photodynamic therapy (PDT) uses a light-sensitive drug and a laser to seal off abnormal blood vessels. PDT is an older treatment for myopic macular degeneration. While it can improve vision in the short-term, it doesn't improve long-term vision as well as anti-VEGF medicines.
If your retina has detached, you will need surgery to fix it. There are a few ways to do the surgery. The procedure your doctor uses depends on how severe the detachment is and other factors.
Complications of Myopic Macular Degeneration
Having high myopia also puts you at risk for retinal tears or detachment. Retinal detachment is when the retina peels away from the blood vessels that feed it oxygen-rich blood. Without a blood supply, cells in the retina can die.
Signs that you have retinal detachment are:
- Flashing lights in your side vision
- Dark specks called floaters in your view
- A curtain that blocks part of your vision
Retinal detachment is a medical emergency. Quick treatment is important to prevent vision loss.
Prevention of Myopic Macular Degeneration
A prompt diagnosis and treatment can help preserve your sight. See your eye doctor for regular eye exams and watch for signs of myopic macular degeneration with an Amsler grid at home.
Severe myopia thins your retinas and makes them more likely to get damaged. Ask your eye doctor if you should wear eye protection during sports and other activities to prevent eye injuries.