Macular degeneration is worsening or impairement of the macula of the eye. The macula is the part of the retina responsible for central vision, which lets you see fine details clearly. The macula is only a small part of the retina but is way more sensitive to detail than the rest of the retina (called the peripheral retina).
All forms of juvenile macular degeneration have similar characteristics. This affects the macula, which lets you see fine details, and it leads to issues with central vision (blurring, distortion or appearance of dark zones). Peripheral vision is usually not affected, but color perception can change in the later stages of the disease.
There is no cure for juvenile macular degeneration, not even a slowing of the progression exists. Wearing sunglasses to protect eyes from UV light can decrease the risk of the disease.