Myopic macular degeneration (MMD) is a type of macular degeneration that can happen when you have myopia, or nearsighted vision. People who develop it have severe myopia. MMD affects your central vision and can get worse over time.
Who Gets It?
Myopia is the most common eye condition in people younger than 40. It makes far away objects look blurry. This happens because your eyeball is larger or longer than usual. That makes the distance between the front of your eye and your retina – the part of your eye that converts light into an image – longer than it should be. That makes you lose sharp focus on objects that are far away.
Having myopia doesn't mean you'll get MMD. You can usually correct your vision with glasses or contacts. It doesn't cause any health risk to your eyes.
When you have severe myopia, you're at risk of getting MMD. Your doctor can measure the severity of your myopia by calculating how powerful a lens you need to correct your vision. Lens power is measured in diopters. If you need lens correction of -6 diopters or more, your myopia is severe.
Your risk of MMD goes up as your myopia severity goes up, especially if it's greater than -10 diopters.
Symptoms
MMD comes on slowly, so you may not notice any symptoms at first. But once there are permanent changes to your retina, they may affect your macula, or the central part of your retina that tells you what's right in front of you. Once your macula gets involved, you have MMD. You may have:
- A blind spot in your central vision
- “Floaters” in your vision
- Wavy or distorted lines
- Missing areas of vision
- Cataracts
- Glaucoma
You may also have vitreous detachment, which is when the gel that fills your eyeball begins to pull away from your retina. You may start seeing flashes of light at the sides of your vision when this happens.
New, abnormal blood vessels may start growing in your eye. These blood vessels can leak and cause scarring, which can lead to vision loss.
Causes
Researchers are still studying what causes MMD. Genetics may play a role. Since eyes with myopia have a specific shape, they're studying the genes at play when it comes to eye shape.
Women may have a slightly higher risk of getting MMD, and your risk may go up if someone in your family has myopia. You have a greater chance of getting it the older you are. MMD also happens more frequently in Asian countries. Chinese Americans get it at a higher rate in the U.S. than other ethnicities.
Diagnosis
An eye specialist, such as an ophthalmologist or optometrist, can diagnose MMD during your regular eye exam. Your doctor may catch it in your childhood or during your teen years. If you or your child have severe nearsightedness, it's important to have regular eye exams.
Your eye doctor will use drops to dilate your eyes. This allows them to see the back of your eye and look more clearly at your retina. They'll search for tears or detachments, glaucoma, and cataracts, as well as new blood vessel growth and blood leakage.
Treatment
There's no medication that can repair problems in your retina caused by MMD. Glasses and contacts can help you see more clearly. You may need thick lenses in your glasses, depending on how severe your myopia is.
When you have MMD, you'll need to see your eye doctor regularly so they can monitor your vision and eye health and watch for problems. They may ask you to use an at-home tool called an Amsler grid to monitor your vision between visits.
An Amsler grid is a square grid with a dot in the center. As you stare at the dot, you can watch to see if any of the surrounding grid lines look wavy or disappear. Your doctor will want to know if they do, since this can be a sign of complications.
If your MMD involves blood leaks from new blood vessel growth, you have wet MMD. You can treat it the same way you treat wet age-related macular degeneration. Your doctor will give you injections of a medication called anti-VEGF. That's a protein your damaged retina releases that promotes blood vessel growth. Anti-VEGF blocks the process that makes this protein.
Treating this problem helps prevent further damage to your eye and slows down your vision loss.
It's important to know that when you have MMD, your thinner retina makes you more prone to eye injury. Your doctor may recommend you wear eye protection during contact activities such as sports that involve a ball.
