What is Stargardt Disease?
Stargardt disease is an inherited eye disorder that causes vision loss.
Specifically, Stargardt disease affects the clarity and sharpness of vision, known as visual acuity. Eye doctors describe normal visual acuity as 20/20 vision, determined by the smallest print size healthy sighted people can read on an eye chart 20 feet away. Visual acuity will deteriorate to 20/200 or worse for most people with the eye condition, according to the National Eye Institute, which the U.S. Social Security Administration (SSA) defines as legally blind. While Stargardt disease may cause vision loss to the point of being legally blind, it rarely causes complete blindness.
Vision loss associated with the disease typically begins in childhood, but vision problems may begin in adults in some forms of the condition. Stargardt disease occurs in about 1 in every 8,000 to 10,000 births, according to the portal for rare diseases, Orphanet.
Stargardt disease is an inherited condition, which means it is passed down through families. About 95 percent of Stargardt disease cases occur when both parents carry the gene mutation.
Symptoms of Stargardt Disease
The signs and symptoms of Stargardt disease typically develop in late childhood or early adulthood. Symptoms usually worsen over time, and may include:
- Loss of vision in both eyes that develops very slowly over time is the primary symptom, specifically, the loss of central vision used for close-up work, such as reading, driving, and recognizing faces
- Trouble with night vision which makes it difficult to get around in low light, or it takes longer to adjust when moving from light to dark environments
- Impaired colour vision
- Grey, black, or hazy spots in the centre of your vision
- Sensitivity to bright light
Yvonne Felix was diagnosed with Stargardt disease at the age of 9. Today she uses her eSight Eyewear to admire details in a painting next to her daughter.
How Stargardt Disease Affects Your Eyes
Stargardt disease develops as the result of a problem with the retina, which is the light-sensitive tissue lining the back of the eye. Light enters the eye, carrying visual information about the world, and strikes the retina. Special photoreceptors in the retina, known as cones and rods, absorb the light and convert the information into pulses. The optic nerve carries these pulses to the brain, which converts the pulses into a visual image.
Specifically, Stargardt disease affects the macula, which sits at the center of the retina. The macula is responsible for central vision and for seeing close-up objects clearly.
Stargardt also affects the rods and cones. Rods are responsible for vision in dim and dark lighting, while cones detect color and fine detail. Rods sit on the outer edges of the retina; cones are in the macula at the centre of the retina. Both rods and cones are affected in patients with Stargardt disease, but the disease tends to affect cones more strongly.
Yvonne Felix is an eSight user living with Stargardt disease.
Rods and cones use vitamin A to make the important light-sensitive molecules inside the photoreceptors. Unfortunately, the manufacture of vitamin A creates harmful byproducts. The human body normally makes a protein that clears away these byproducts.
In people with Stargardt disease however, mutations in the gene that make the protein can prevent the body from clearing away the vitamin A byproducts. Clumps of lipofuscin, a fatty substance that forms yellowish flecks, can accumulate in the cells that lack the protein. These clumps can build up in and around the macula to damage photoreceptor cells and impair central vision. The more the clumps build up, the worse vision gets. In time, the clumps lead to the death of the photoreceptors and very poor visual acuity.
To diagnose Stargardt disease, eye care professionals look for lipofuscin, which usually appear as yellow flecks on the macula. The flecks typically have an irregular shape and usually extend outward from the macula in a ring-like pattern. The size, number, appearance and color of the lipofuscin flecks vary.
An eye care professional may also test the patient’s visual field to identify loss of central vision and perform tests to evaluate the patient’s color vision. They may conduct tests such as a fundus photo of the retina that may reveal the presence of fundus, electroretinography (ERG) to measure the electrical response of rods and cones to light, and optical coherence tomography (OCT) that looks for damage to the retina.
Maintaining your Remaining Vision
There are things you can do to make the most of the sight you have left, and take care of your eyes as best as possible.
- Avoid excess vitamin A as it’s believed that those with Stargardt’s cannot process it properly
- Visit your eyecare provider for an eye test at least every 2 years
- Quit smoking and avoid second-hand smoke
- Keep your weight and blood pressure at a healthy level
- Wear sunglasses that can block UV and blue light
- Wear wide-brim hats or hats with visors to protect your eyes from direct sunlight
- Restrict alcohol intake to recommended levels
- Consume lots of fruits and vegetables
While navigating a life with Stargardt disease can be difficult, there are resources and support groups at your disposal.
- FB – Stargardt Disease Support Group: supports those who have Stargardt’s or those who know someone with Stargardt’s
- FB – Stargardt’s Support Group: brings together those affected by Stargardt’s worldwide
- The Stargardt Team: hosts a platform for those with Stargardt’s to post photos and information about living with low vision, also has a “Stargardt Room” in the message boards
- Stargardt’s Network: meets monthly and allows members and their family to connect and share resources and advice for managing a life with low vision
- Stargardt’s Connected: raises awareness and gives support to those with Stargardt’s, and assists in progressing towards a cure
- FamilyConnect: gives parents and other family members of visually impaired children a supportive place for sharing and finding resources on raising their children
Research in the field of Stargardt’s disease is constantly advancing. Here are some reputable scientific sources to keep an eye on for new Stargardt’s-related discoveries.
- eyeGENE: genomic medicine initiative created by the National Eye Institute that facilitates research into causes and mechanisms of rare inherited eye diseases
- ProgStar: conducts research and provides study reports for Stargardt’s
- ClinicalTrials.gov: lists ongoing and completed research trials related to Stargardt’s disease
- My Retina Tracker: research database of people affected by retinal degenerative diseases such as Stargardt’s
Stargardt’s disease progresses differently for everyone. Visual acuity may decrease slowly to begin with, but once you reach a visual acuity of about 20/40, deterioration typically quickens until it reaches 20/200 (whereas “normal” vision is about 20/20). Over time, almost everyone with Stargardt’s lives with a visual acuity of 20/200 to 20/400. Nonetheless, there are still solutions to help enhance your remaining vision.
Stargardt Disease Treatments
There are currently no treatments available because the retina is too fragile to be involved in surgeries without risk of damaging it or tearing it.
Research in the field is currently highly active in the United States and Europe. Some researchers have seen positive results in stem cell and gene therapy but there have been no definitive conclusions yet. Stronger glasses are not a possible solution because they only work for defective corneas, not defective retinas.
There’s currently a gene therapy clinical trial in the US and France that replaces the mutated copies of the gene ABCA4. This is not yet commercially available.
Human embryonic stem cell transplant has shown potential as a treatment for Stargardt’s disease. Further trials are scheduled.
Some prevention pharmaceuticals are under development targeting the lipofuscin accumulation associated with Stargardt’s disease.
Low Vision Eyewear for Stargardt Disease
Many people who live with Stargardt’s disease opt to purchase eSight, which is an electronic eyewear for those with low vision. It stimulates synaptic activity from the remaining photoreceptor function of its users’ eyes and provides the brain with increased visual information to naturally compensate for gaps in the user’s field of view, which is typically central vision loss in the case of Stargardt’s.
For those who are legally blind, eSight is clinically validated to enhance vision to up to 7 lines on a doctor’s eye chart. It has a leading edge camera, liquid lens, and high definition display powered by smart algorithms. The high-speed, high-resolution 21.5 MP camera captures and then projects real-time footage onto two OLED screens in front of the eyes.
eSight and Stargardt’s
eSight was founded as a hopeful solution to Stargardt’s disease. Founder Conrad Lewis wanted to help his two legally blind sisters see again. After about 30 years of tinkering, and 7 more years of research and development, the first eSight prototype was released in 2013. Today, 8 out of 10 people with Stargardt’s disease who try eSight experience enhanced vision.
eSight changes lives for those who thought they would never be able to see the details on the street sign across the road, and who hadn’t seen their family’s faces in years.
Does Stargardt’s Disease go by any other names?
Stargardt’s disease is also referred to as “Stargardt muscular atrophy” and “fundus flavimaculatus.”
What is juvenile macular degeneration (JMD)?
Also known as juvenile macular dystrophy, this is a group of inherited eye disorders that affects children and young adults. While Stargardt’s is the most common form of JMD, other types include juvenile retinoschisis and Best’s disease.
How is Stargardt’s related to age-related macular degeneration (AMD)?
Stargardt’s disease and macular degeneration are both symptomatically similar as they are both macular degenerative diseases.
Can Stargardt’s disease only manifest in early childhood or adolescence?
No, there have been reports of cases of late-onset Stargardt’s as well.
Have stem cells been proven to treat Stargardt’s?
Human embryonic stem cells hold promise for treating macular-degenerative eye conditions in the future, but scientists are still doing research.
Is Stargardt’s hereditary?
Yes, Stargardt’s is a genetic disease that is inherited from parents who possess the mutated gene. It is typically realized as an autosomal recessive disorder although there have been cases resulting from a dominant form of inheritance (i.e. only one parent having the mutated gene).