Juvenile macular degeneration (JMD) is a broad term used to describe several eye disorders that primarily affect infants, children, and young adults. These conditions are associated with genetic mutations that affect the macula and cause malfunction and eventual death of cone cells, which are responsible for central vision.
Types of JMD
Stargardt's disease is the most common type of JMD and affects one in 10,000 people. Symptoms usually develop between the ages of 7 and 12, although some people do not experience visual impairment until their 30s or 40s. Manifestation of Stargardt's includes yellow spots composed of the pigment lipofuscein, scarring of the macula, and central vision loss.
Most patients with Stargardt's experience central vision loss by the time they reach adulthood. The progression of visual loss varies, but one study found that by age 50, one-half of participants had reached legal blindness. In late stages of the disease, color vision may also be impaired.
Stargardt's disease is an inherited autosomal recessive syndrome, which means that both parents carry the defective gene but have normal retinas. There is a 25 percent chance that their child will be born with Stargardt's disease. Children who are unaffected are unlikely to pass along the trait, unless they have a child with someone who has Stargardt's or carries the gene.
A variation of this disorder is fundus flavimaculatus. Symptoms are similar, but the eye shows yellow-white spots and flecks of various shapes and minimal changes in the macula. Fundus flavimaculatus has a more favorable prognosis and symptoms often do not develop until young adulthood.
Best's vitelliform retinal dystrophy is the second most common type of JMD. The age of onset and severity of symptoms vary greatly, even among family members and it is usually diagnosed during childhood or adolescence.
In its early stages, a large, yellow, cyst-like drusen resembling an egg yolk forms under the retinal pigment epithelial (RPE) cells. Despite the cyst, vision often remains normal, or nearly normal, for many years. Eventually the cyst ruptures and the fluid and yellow deposits spread beneath the macula.
Once the cyst ruptures, degeneration of the macula and RPE cells begins, causing vision loss. Central vision may deteriorate to about 20/100 later in life. Peripheral vision usually remains unaffected, and Best's does not always affect both eyes equally. Many patients retain good central vision in at least one eye and sometimes, Best's disease does not cause significant central vision loss.
It has an autosomal dominant pattern of inheritance, which means that an affected person has one Best gene, paired with one normal gene. Affected individuals have a 50 percent chance of passing the disease-causing gene to a child, even if their partner is unaffected.
JMD Treatment and Prevention
There is no treatment for JMD disorders. The disorders that cause neovascularization and leakage may respond to laser treatment, but there are no standard therapies.
Genetic testing and counseling may assist with family planning.