What to know about juvenile macular degeneration

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JMD collectively refers to a group of rare, inherited eye disorders causing the deterioration of the macula in children and young adults. A person acquires these conditions from their parents, with each having its own inheritance pattern.

With all forms of JMD, genetic alterations cause damage to the macula, leading to central vision loss. Their presentation and progression vary greatly.

Typically, JMD presents early in childhood and can cause vision to deteriorate quickly. However, in other cases, many people may be unaware they have JMD as they can keep useful vision into early adulthood.

According to the American Academy of Ophthalmology, the three most common forms of JMD include:

• Stargardt disease
• Best’s disease, also known as Best’s vitelliform retinal dystrophy
• juvenile retinoschisis, also known as X-linked juvenile retinoschisis

All forms of JMD cause problems with central vision. Symptoms typically appear in early childhood but may also present later. Some children do not show signs, and a healthcare professional may identify the eye problem incidentally during a check-up or school screening.

The symptoms and speed of vision loss vary depending on the type of JMD.

Stargardt disease

Stargardt disease is the most common type of JMD. It affects roughly 1 in every 10,000 children. Symptoms typically appear in late childhood to early adulthood and occur due to changes in the ABCA4, ELOVL4, and PROM1 genes.

The most common symptom is the gradual loss of central vision in both eyes. While most people only lose their central vision, some may also lose their peripheral vision. Vision may rapidly deteriorate until it reaches roughly 20/200.

Individuals often notice poor vision before an eye doctor can see any ophthalmologic changes. Other symptoms of Stargardt disease can include:

• loss of visual acuity
• loss of color vision
• hazy, gray, or black spots in the center of vision
• light sensitivity
• eyes needing more time to adjust when moving from light to dark areas

Best’s disease

Best’s disease, also known as Best vitelliform macular dystrophy (BVMD), is the most common form of dystrophinopathy. This refers to conditions that occur due to changes in the BEST1 gene.

It may affect between 1 and 9 out of every 100,000 people and typically starts to cause changes in the macula between the ages of 3 and 15.

A person with Best’s disease may have normal vision for decades and not notice a decline in vision. Many people are unaware that they have the condition until a healthcare professional discovers it during an eye exam.

The person may have a yellow cyst that looks like a sunny-side-up egg under the macula. This cyst contains a fatty yellow pigment known as lipofuscin. If the cyst ruptures, it will leave yellow deposits that look similar to scrambled eggs.

Other symptoms of BVMD include:

• blurred vision
• loss of central vision but not peripheral vision
• affecting just one eye or, in bilateral cases, one eye more severely than the other

Juvenile retinoschisis

Juvenile retinoschisis, also known as X-linked juvenile retinoschisis, refers to a condition that occurs almost exclusively in males due to inheriting a change in a gene on the X chromosome called RS1. It occurs in roughly 1 in 5,000–25,000 males worldwide.

The main symptom of juvenile retinoschisis is a reduction in visual acuity. While it can vary, vision is typically in the 20/60 to 20/120 range. A person typically receives a diagnosis between the ages of 3 months and school age with symptoms that can include:

• amblyopia (‘lazy eye’)
• nystagmus (involuntary eye movements)
• strabismus (squint)

All types of JMD occur as a result of genetic variations in one or more genes that a person inherits from their parents.

Stargardt disease occurs due to genetic alterations, notably in the ABCA4 gene. This gene codes for a protein that transports toxic substances out of photoreceptor cells. If this protein is not functioning correctly, the toxic material builds up in yellowish clumps (lipofuscin) on the macula, causing cell dysfunction and the death of photoreceptor cells.

Best’s disease occurs due to variations in the BEST1 gene. Some may also refer to this gene as VMD2. The BEST1 gene is also involved in the transfer of chemicals between cells in the retina. Changes in this gene can result in the accumulation of fluid and lipofuscin in the retinal tissue.

Juvenile retinoschisis is an autosomal recessive disease (passing from both parents to the child) that is linked with an alteration in the RS1 gene on the X chromosome. As such, this condition mostly affects individuals assigned male at birth as they typically possess one X chromosome.

The RS1 gene is responsible for encoding retinoschisis. This protein plays a role in the development and maintenance of the retina and likely helps adhere layers of the retina together.

Risk factors

JMD is an inherited genetic disorder, meaning children typically inherit it from their parents. If their parents have the condition or are carriers, the child is at a higher risk of JMD. However, the inheritance pattern of each type of JMD is different:

• Stargardt disease can have different inheritance patterns. For example, ABCA4 follows a recessive pattern, meaning a person needs to inherit two copies of the gene variation (one from each parent). ELOVL4 follows a dominant pattern, meaning a person only requires one copy of the gene alteration (from one parent).
• Best’s disease follows a dominant inheritance pattern, meaning a child may develop the condition if they inherit one copy of a gene variation.
• Juvenile retinoschisis is an X-linked recessive disorder. This is why it is more common in males, as they typically have one X chromosome and thus only require one gene variation. In females, who typically have two X chromosomes, they would require an alteration in both copies of the gene.

An eye doctor diagnoses JMD using a combination of clinical findings, imaging tests, and genetic testing. In some cases, an eye doctor may identify JMD during a routine eye exam.

Additionally, a doctor may use family history to determine a person’s risk. Special labs that conduct genetic testing can help identify the exact gene that causes the disease.

Each type of JMD presents with its own characteristic findings in an eye exam:

• Stargardt disease: Yellowish-white flecks in or around the macula and atrophy of the retinal pigment epithelium, which is the thin pigmented layer that supports the retina.
• Best’s disease: A bright yellow fluid-filled sac that looks like an egg yolk in the macula and may also have yellow flecks.
• Juvenile retinoschisis: Tiny splits in the retinal layers and cavities filled with blood vessels and blisters. Over time, blood may leak into the vitreous — the fluid that fills the eye — leading to retinal detachment.

The eye doctor may also proceed with other tests to confirm the diagnosis and rule out other conditions:

• Optical coherence tomography (OCT): A noninvasive test that uses laser scans to take images of the retina.
• Fluorescein angiography: This test involves an injection of a dye into the vein in the arm to highlight blood vessels in the retina.
• Electroretinography (ERG): This diagnostic test measures the retina’s electrical activity in response to a light stimulus.

Currently, there is no cure for JMD. However, there are several treatment modalities under trial, including gene therapy, pharmacologic treatment, and stem cell transplantation. These treatment options may help to slow the progression of the disease and prevent vision loss.

Doctors may recommend several strategies to help individuals manage their condition and potential vision loss, including:

• low-vision aids such as pocket telescopes
• orientation and mobility training
• assistive technologies such as talk-to-text, screen magnification, and screen-reading software
• the use of eye protection such as sunglasses, hats, and umbrellas

Access information and resources about eye health here.

JMD and AMD are both caused by conditions that damage the macula. However, JMD is the result of a genetic alteration, while AMD occurs as part of the body’s natural aging process.

Additionally, as the names suggest, symptoms of JMD present in children and young adults, while AMD is most commonly associated with older adults.

JMD describes a group of rare inherited eye diseases. While different types of JMD may vary in their presentation and course of the disease, all types result from genetic variations and lead to a gradual loss of central vision.

These conditions differ from AMD as they typically present in childhood and do not occur as part of the natural aging process.