Stargardt's disease (fundus flavimaculatus)
While macular degeneration generally is associated with ageing 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 characterised 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’s 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 themselves may not have the disease.
Researchers have found that about 5% 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 it’s possible for up to half of the children of a single affected parent to develop the condition. Also, you can’t predict how much vision a child may lose to Stargardt’s disease based on the affected parent’s vision loss.
How fast does Stargardt’s progress?
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.
But 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 6/15 to 6/60 on a standard eye chart. (In the UK, legal blindness is defined as visual acuity of between 3/60 and 6/60 with a severe reduction of visual field 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 late stages of Stargardt’s, colour 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% of UV light to reduce the possibility of additional eye damage caused by the sun.
If you have Stargardt’s, your eye care professional also may suggest that you wear spectacles with specially tinted lenses to block certain wavelengths of light.
One company that has pursued development of a treatment for Stargardt’s disease is Astellas (formerly Ocata Therapeutics). This stem cell treatment is designed to protect and regenerate photoreceptors in the retina that are damaged by eye diseases like Stargardt’s. Results from Phase I and Phase II clinical trials were encouraging, with significant vision improvements reported for some patients.
Other research suggests 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.”
Acucela is another company with a drug candidate for Stargardt’s disease in Phase III clinical trials. The company’s drug — called Emixustat — works by slowing the buildup of toxic waste products that lead to retinal degeneration.
Sanofi is working on a gene therapy trial for Stargardt disease. The treatment replaces mutated copies of the gene ABCA4 with healthy copies.
Opsis Therapeutics is a company that is developing technology to replace degenerated cells in the retina to restore vision in people with Stargardt’s disease. The company is fabricating retinal cell grafts from stem cells and biocompatible materials for delivery of the cell grafts to the retina via standard surgical techniques.
Coping with Stargardt’s disease
The American Macular Degeneration Foundation recommends that people with Stargardt’s or a history of the eye disease in close family members obtain genetic counselling before starting their own families.
Because vision loss often appears in young children with Stargardt’s, low vision counselling from your eye care professional 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.
FIND AN OPTICIAN: if you're concerned about your vision, visit an optician near you.
Phenotypic variation in a family with pseudodominant Stargardt disease. <em>JAMA Ophthalmology</em>. March 2016 [e-pub ahead of print].<br> Makindus receives orphan designation for MI-100 for Stargardt's disease. June 2014. www.makindus.com. Accessed March 2016.<br> ACT announces first Stargardt patient treated with higher dosage of embryonic stem cell-derived retinal pigment epithelial cells. Advanced Cell Technology. Press release. July 2012.<br> Columbia researchers work on preventing blindness from age-related macular degeneration and Stargardt's disease. Columbia University Medical Center. Press release. May 2011.<br> C20-D3-vitamin A slows lipofuscin accumulation and electrophysiological retinal degeneration in a mouse model of Stargardt disease. <em>The Journal of Biological Chemistry</em>. March 2011.<br> Alkeus Pharmaceuticals licenses novel compounds from Columbia University for potential treatments of ophthalmologic conditions such as dry-AMD and Stargardt disease. Alkeus Pharmaceuticals. January 2011. www.alkeuspharma.com. Accessed March 2016.<br> <em>Ophthalmology, 2nd ed</em>. 2004.
Page published on Wednesday, 16 March 2022
Page updated on Wednesday, 16 March 2022