context: Juvenile macular degeneration ( JMD) is the term for several inherited and rare diseases that affect children and young adults. They include Stargardt's disease, Best disease, and juvenile retinoschisis. They can cause central vision loss that often starts in childhood or young adulthood. These conditions come from gene changes passed down in families. Unfortunately, there's no treatment. Visual aids, adaptive training, and other tools can help young people with vision loss remain active. Researchers continue to look for ways to prevent and treat JMD. Genetic counseling can teach parents about these eye problems and sort out the risks for their children. Counseling also helps families understand how their loved one's vision is affected. JMD damages the macula, the tissue in the center of your retina at the back of your eye. This area provides the sharp central vision that lets us do things like read and drive. It also allows us to see color and recognize faces. There's a variety of inherited diseases that can lead to JMD. It's the most common form of JMD. It's named after German eye doctor Karl Stargardt, who discovered it in 1901. It affects about one in 10,000 children in the U. S. Although the disease starts before age 20, you may not notice vision loss until age 30 to 40. Signs: It's usually diagnosed by yellow-white spots that appear in and around the macula. If they cover the back of the eye, then it is called fundus flavimaculatus. These deposits are an abnormal buildup of a fatty substance produced during normal cell activity. Symptoms: Include trouble reading and gray or black spots in your central vision. Loss of sight comes on slowly, then affects both eyes. Once vision reaches 20/40, the disease moves faster, until your vision reaches 20/200, which is legal blindness. Some people lose vision quickly over a few months. Most people will have vision loss ranging from 20/100 to 20/400 by the time they're 30 or 40. It doesn't affect peripheral, or side, vision. You probably won't lose night vision, but you might have trouble when you have to switch from dark to light places. Color vision goes away in later stages of the disease. Causes: Researchers blame a specific gene for the disease. If both parents carry one mutated form of the gene and one normal gene, their children have a 25% chance of getting the disease. Children who inherit only one mutated gene won't get it. But they can pass it on without knowing it. It's the second-most common type of JMD. You might also hear it called Best vitelliform macular dystrophy. It was discovered in 1905 by Friedrich Best, another German eye doctor. It may show up on an eye exam between ages 3 and 15, but symptoms may not show up until later. Signs: The eye doctor will see a bright yellow fluid-filled sac, or cyst, under your macula. It looks like a sunny-side-up egg. Your vision may be normal or near normal at this stage. Eventually, the sac bursts, and the fluid spreads throughout your macula. The doctor can spot it with an instrument called an ophthalmoscope. Symptoms: Show up in stages over a period of years. Early on, there's no change. Later stages involve central vision loss in one or both eyes. Things will look blurry or warped. Your central vision could drop to 20/100 in later stages. But you might not have serious vision loss. Or you could lose vision in one eye, but not the other. Causes. If one parent has Best disease and one doesn't, there's a 50% chance their kids will get it. Children who don't develop the disease can't pass it on to their children. Also called X-linked retinoschisis, it mostly affects young males. Vision loss happens between ages 10 and 20 and remains stable until around age 50 or 60. Signs: This condition causes your retina to split into two layers. Blisters and blood vessels fill the space between them. Blood leaks into the vitreous fluid, the clear liquid that fills the inside of your eye. Over time, the vitreous fluid may pull away from your retina. Or the retina can detach from the inside wall of your eye. Symptoms: It causes central vision loss between 20/60 and 20/120. You might find it hard to focus both eyes on one object (strabismus). Or your eye might move on its own (nystagmus). About half of people with the disease lose side vision. By age 60 or older, you might be legally blind. Causes: The abnormal gene at fault is linked to the X chromosome. That means it behaves differently in women and men: There's a 50% chance that women who carry the gene will pass it on to their daughters, who will become carriers. They also have a 50% chance of passing it to their sons, who will get the disease. Men with the disease always pass it to their daughters, who then become carriers. But they can't pass the gene to their sons. As with other types of juvenile macular degeneration, there is no treatment. But surgery can help repair detached retinas.