This article provides an overview of JMD, including the symptoms and causes of Stargardt’s disease, Best disease, and juvenile retinoschisis.
What Does Early Onset Macular Degeneration Mean?
Early onset macular degeneration is another term for JMD. Sometimes it is also called juvenile macular dystrophy.
JMD is a different condition than the more commonly known age-related macular degeneration (AMD). AMD occurs due to the body’s natural aging process, usually in people aged 65 or older. JMD is a genetic, inherited condition that affects children and young adults.
Similar to AMD, central vision loss occurs in JMD due to degeneration of the macula. The macula is a small, oval-shaped part of the retina (a light-sensitive layer of tissue lining the back of the eyeball).
The functions of the macula include central vision, the ability to see color, and the ability to see fine details like small print on a pill bottle or a road sign in the distance. Losing central vision can greatly impact a child’s engagement in everyday life, from schoolwork to driving to playing sports.
There is no cure for JMD, but early diagnosis can lead to better outcomes by implementing various therapeutic approaches. This can include prescription medications, stem cell transplants, gene therapy, and assistive devices.
Genetic Counseling and JMD
Because JMD is a genetic, inherited disorder, a person will likely have to undergo genetic testing for an accurate diagnosis. This could be preterm (before an embryo is implanted or a baby is born) or when a child first presents symptoms.
However, the American Academy of Ophthalmology’s task force on genetic testing warns that there can be risks to genetic testing, like any other medical intervention. These include impacts on family planning, altering relationships with children or other members of the family, or even creating a sense of guilt and anxiety.
Instead, skilled genetic counseling for parents or children who undergo genetic testing for eye diseases like JMD is recommended. This could help parents who both carry genes for Stargardt’s disease to make a decision on embryo implantation or help a newly diagnosed child and their family learn about their prognosis.
Stargardt’s Disease
Stargardt’s disease is the most common form of JMD, occurring in about 1 in 10,000 children. It affects the photoreceptors in the eyes that absorb light, causing them to die.
Signs and Symptoms of Stargardt’s Disease
Symptoms of Stargardt’s disease typically start in the first or second decade of life. They include:
Worsening visual acuity (clarity of vision) Loss of color vision Blurred, distorted, or dark spots in the central visual field Difficulty adjusting vision between bright and dark settings Poor vision occurring before any changes are noticed in the ophthalmoscope (the tool used to look at the back of the eye) Bilateral symmetry (same symptoms in both eyes) Peripheral (side) vision that may be unaffected and stay intact
Stargardt’s disease typically progresses to 20/200 vision, meaning you can see at 20 feet what other people see at 200 feet. This is considered being legally blind.
The progression of vision loss is different from person to person. However a typical pattern is vision loss that begins slowly, speeds up once a person reaches 20/40 vision, and eventually levels off.
Causes of Stargardt’s Macular Degeneration
Stargardt’s disease is often due to mutations in the ABCA4 gene. This mutation causes photoreceptors in the eye to die.
ABCA4 is an autosomal recessive gene. This means that both the mother and father must possess an ABCA4 allele and pass this on to the child. In some cases, one or both parents might have Stargardt’s disease themselves. In other cases, both parents may be recessive carriers and are unaware of the gene.
Best Disease
Best disease, also called Best vitelliform macular dystrophy, is an eye condition that causes progressive vision loss.
Signs and Symptoms of Best Disease
Symptoms of Best disease can begin in childhood, early adulthood, or even adulthood. Symptoms include:
Characteristic deposits of yellow, egg yolk–like material under the maculaWorsening visual acuityBlurred central visionNo change in ability to adjust from bright to dark settingsUsually affects both eyes equally, but occasionally only one eye is affectedPeripheral (side) vision may be unaffected and stay intact
Best disease usually progresses at a slow, constant rate. A person with Best disease may have nearly normal vision for many decades.
Causes of Best Disease
Best disease is caused by a mutation in the BEST1 gene, also sometimes referred to as the VMD2 gene. This leads to breakdown of the retinal pigment epithelium tissue in the retina.
The BEST1 mutation is inherited in an autosomal dominant pattern, which means only one parent needs to possess the mutated gene and pass it on for the child to develop the condition.
Juvenile Retinoschisis
Juvenile retinoschisis, also called X-linked juvenile retinoschisis, is the main type of JMD in boys, due to how it is inherited. Prevalence estimates range from 1 in 5,000 to 1 in 25,000 individuals.
Signs and Symptoms of Juvenile Retinoschisis
Symptoms of juvenile retinoschisis usually begin between the first and second decade of life. They include:
Worsening visual acuityLoss of color visionBlurred central visionClouding of the lens of the eyeAbnormal eye movementsBilaterally asymmetric (affects both eyes, but one may be worse than the other)Side (peripheral) vision may be impairedComplications including retinal detachment or blood vessel leaks
Juvenile retinoschisis symptoms are typically found in young boys and will progressively worsen over time. Vision typically worsens in childhood, before stabilizing for a period of time. Vision may worsen again when the person reaches their 50s or 60s.
Causes of Juvenile Retinoschisis
Juvenile retinoschisis is caused by a mutation in the RS1 gene. This mutation impacts production of the retinoschisin protein, which can lead to splits or tears in the retina.
The RS1 gene is located on the X-chromosome and is passed down through an X-linked inheritance pattern. Boys inherit this condition from their mothers, because the father passes on the Y chromosome.
Coping With Vision Loss in Children
JMD is unfortunately not curable at this time. This can be difficult to accept, and it’s understandable that you and your child may have difficulty adjusting to your new reality. Talking to a counselor or therapist may help you both cope.
There are some treatments available that may slow progression or prevent complications of JMD. These differ based on what type of JMD a child has, and your ophthalmologist can provide recommendations.
Assistive devices can also help your child adjust to life with vision loss and stay involved in their meaningful occupations, like school and play. These might be recommended by their eye specialist, occupational therapist, or vision rehabilitation therapist.
Examples of assistive devices for JMD include:
EyeglassesHandheld, stand, or video magnifiersTelescopesLarge-print books or worksheetsAudio books
Occupational therapists or vision rehabilitation therapists can also help your child learn new ways of using their eyes as they adjust to their sight changes. For children with JMD, this might include a technique called eccentric viewing, which helps maximize their intact side (peripheral) vision when central vision is blurred or lost.
Summary
JMD is an inherited eye disease that affects central vision in children and young people. There are multiple types of JMD, including Stargardt’s disease, Best disease, and juvenile retinoschisis. Each is caused by mutations in different genes with different inheritance patterns. While there is no cure for JMD, there are various treatments and therapies that can help your child cope.
A Word From Verywell
Learning that your child has JMD and will lose their vision can be a shock. You may be worried that your child won’t be able to play, learn, or grow up like other kids. Some parents also experience guilt, due to the heritable nature of JMD. A genetic counselor or therapist can help you through these emotions and adjust to life with JMD. While JMD is a serious condition that leads to significant vision loss, know that your child can still live a very full life with the help of assistive devices and various therapies.
