While macular degeneration generally is associated with aging eyes, an inherited form known as Stargardt’s disease can affect children and young adults.
Stargardt’s disease — also called fundus flavimaculatus or Stargardt’s macular dystrophy (SMD) — affects approximately one in 10,000 people and is characterized by central vision loss early in life. (Some researchers believe a distinction should be made between Stargardt’s disease and fundus flavimaculatus because they say each describes a different variant of the eye disease.)
Stargardt generally refers to a group of inherited diseases causing light-sensitive cells in the inner back of the eye (retina) to deteriorate, particularly in the area of the macula where fine focusing occurs. Central vision loss also occurs, while peripheral vision usually is retained.
Stargardt’s disease is diagnosed by the presence of small, yellowish spots of deteriorating tissue (drusen) sloughed off from the colored or outer covering of the retina (retinal pigment epithelium). Progressive vision loss eventually leads to blindness in most cases.
What Causes Stargardt’s Disease?
Stargardt’s is an inherited disease passed along to children when both parents carry mutations of a gene associated with vitamin A processing in the eye. Parents can carry recessive genetic traits responsible for Stargardt’s, even though they may not have the disease.
Researchers have found that about 5 percent of people carry gene mutations that cause inherited retinal diseases such as Stargardt’s disease and retinitis pigmentosa. However, the inheritance pattern of Stargardt’s is variable, and up to half of the children of a single-affected parent can develop the condition. Also, the degree of vision loss caused by Stargardt’s disease can be more severe or less severe in children, compared with that experienced by an affected parent.
Vision loss from Stargardt’s generally begins to show up within the first 20 years of a young person’s life, particularly in early childhood.
How Fast Does Stargardt Progress?
However, it’s difficult to pinpoint exactly when retinal damage will occur or how fast it will progress because variations can occur even among family members with similar inherited tendencies.
In some cases, signs of Stargardt’s disease appear in early childhood; but a person with Stargardt’s (particularly the fundus flavimaculatus version of the disease) may reach middle age before vision problems are noticed.
Stargardt’s disease causes vision loss in the range of 20/50 to 20/200 on a standard eye chart. (In the United States, legal blindness is defined as visual acuity of 20/200 or worse while wearing corrective lenses.) Those who have the fundus flavimaculatus form of the disease, however, are likely to experience even more severe vision loss.
Symptoms of Stargardt’s disease can include blurry or distorted vision, inability to see in low lighting, and difficulty recognizing familiar faces. In the late stages of Stargardt’s, color vision also may be lost.
Can Stargardt’s Disease Be Prevented Or Treated?
Some research indicates that exposure to bright light may play a role in triggering the retinal damage that occurs with Stargardt’s. While there is no known treatment for Stargardt’s disease at this time, people with the condition often are advised to wear eyeglasses or sunglasses that block 100 percent of UV light to reduce the possibility of additional eye damage caused by the sun.
If you have Stargardt’s, your eye doctor also may suggest that you wear eyeglasses with specially tinted lenses to block certain wavelengths of light.
One company developing a treatment for Stargardt’s disease is Ocata Therapeutics, Inc. In March 2010, the company received an orphan drug designation from the U.S. FDA for a stem cell treatment designed to protect and regenerate photoreceptors in the retina that are damaged by eye diseases like Stargardt’s.
The company is enrolling patients in clinical trials in the U.S. and U.K. It also recently reported outcomes of the treatment in four Korean men with macular degeneration (two of whom had Stargardt’s). None of the patients experienced visual deterioration after receiving treatment. Better still, three of the men experienced vision improvements in their treated eyes in the year following the procedure.
In February 2016, Ocata was acquired by Astellas Pharma, based in Tokyo, Japan.
Studies suggest aggregation or “clumping” of vitamin A in the retina may be associated both with Stargardt’s disease and age-related macular degeneration (AMD). These clumpy deposits are known as “vitamin A dimers.”
In studies conducted at Columbia University Medical Center (New York) in 2011, researchers created an altered form of vitamin A that appears to slow the formation of vitamin A dimers in the eye when given to mice with the same genetic defect as humans with Stargardt’s disease.
Also, the modified vitamin A behaved exactly as normal vitamin A does in all other aspects, making it an attractive potential therapy for preventing blindness in humans, the researchers said.
The research team was led by led by Ilyas Washington, PhD, a professor in the Department of Ophthalmology at Columbia’s Harkness Eye Institute.
Dr Washington’s lab has been awarded a $1.25 million grant from the National Eye Institute to investigate further the link between vitamin A dimers and various retinal degenerations, which could result in new approaches to treat these diseases.
Alkeus Pharmaceuticals has licensed from Columbia certain patents relating to Dr Washington’s discoveries and has begun enrolling patients in clinical trials to treat Stargardt’s disease.
Makindus, Inc., a specialty pharmaceutical company, also has received FDA orphan drug designation for MI-100 to treat Stargardt’s disease. MI-100 is a novel formulation of a legacy compound that has been shown to have a clinical effect in improving visual acuity for Stargardt’s patients in an investigator-initiated clinical trial.
Makindus plans to file a New Drug Application (NDA) and is preparing for Phase 3 testing of MI-100.
Coping With Stargardt’s Disease
The American Macular Degeneration Foundation recommends that people with Stargardt’s or a history of eye disease in close family members obtain genetic counseling before starting their own families.
Because vision loss often appears in young children with Stargardt’s, low vision counseling from your eye doctor is essential to make sure that classroom learning is not hampered. For example, a child with Stargardt’s may need to use large print books and special devices that magnify print.