Stargardt’s disease or fundus flavimaculatus is an inherited eye condition similar to age-related macular degeneration but appearing mostly in children and young adults. The first symptoms occur before the age of 20, girls and boys being equally affected and prone to developing this condition.
According to statistical data, Stargardt’s macular dystrophy affects 1 out of every 20,000 kids and young adults, the progression of visual impairments induced by this disorder being variable. Getting worse with age, this condition generally leads to severe vision loss and eventually to blindness.
What causes Stargardt’s disease?
As said before, the ailment is inherited so genetics plays the main role in its occurrence. In most cases both parents are carriers of the altered gene thus the disease is considered autosomal recessive. Each child has 25% chances of inheriting it, whether the parents manifest the ailment’s symptoms or not. In fact, in most cases parents don’t even know they have this disorder until their child is diagnosed.
The gene responsible for Stargardt’s macular dystrophy, called ABCR, produces a protein which transports energy from and to photoreceptors in retina. In a healthy organism, images form on the retina but when the ABCR gene’s functioning is altered by mutations, energy doesn’t reach cells in retina layers anymore. Moreover, the non-functional protein allows fatty substances to buildup inside the retina layers, causing flecks which prevent images from forming so vision loss occurs.
Excessive exposure to intense light also seems to have a role in this ailment’s evolution, according to recent studies, but this factor alone can’t determine the onset of Stargardt’s disease.
Specific signs and symptoms
In the early stages of the ailment, patients generally have a good visual acuity but accuse increased light sensitivity, difficulties adapting to dark after exposure to light and also difficulties in reading in dim lighting. The sharpness of sight decreases rapidly and color vision impairments occur, most persons affected by this disorder experiencing bilateral decreased central vision during childhood.
While a healthy person has a visual acuity of 20/20, in a patient with Stargardt’s disease the starting value is 20/40. At this stage the ailment’s symptoms are already present and sight is severely affected. The evolution is quite rapid, by age 50 almost half of all patients having a visual acuity of 20/200, which stands for legal blindness.
How is the condition diagnosed?
Visual acuity tests and color vision exams can guide the diagnosis but the problem is most of the times the ailment passes unnoticed in its first stages and retina appears normal upon examination. So the first abnormalities are seen in routine exams when the disorder is already advanced. Once the diagnosis is confirmed, specific tests including fluorescein angiography can be performed for identifying the damaged areas of the retina.
Prevention and treatment alternatives
Preventing this condition is not really possible being given its genetic character but some measurements can surely be taken for slowing down its evolution. Some studies suggest wearing eyeglasses with UV protection can delay the worsening of symptoms, as the special filters incorporated in eyeglasses can block certain wavelengths, preventing damaging light from entering the eye.
Reducing the intake of fat foods and eliminating caffeine and sodas also seems to help, as these unhealthy eating habits are linked with an increased risk of developing Stargardt’s disease. Then, alcohol consumption and smoking should be completely eliminated as the first one reduces the levels of certain substances known to protect the eyes and the second one stimulates the production of toxins inside the organism.
Eye multivitamin complexes can be a solution for delaying the symptoms as long as they don’t include vitamin A, which was proven to actually worsen the ailment. Although generally considered a must for a healthy vision, vitamin A seems to have a negative effect in people with this disorder, as the altered genes lead to an abnormal synthesis and buildup of this vitamin in the eyes, accelerating vision loss.
There is no known treatment for Stargardt’s disease at this time but researchers hope gene therapy and stem cells therapy will bring positive results, although no tests were taken on human subjects yet.