Stargardt disease

Stargardt disease, or fundus flavimaculatus, is an inherited juvenile macular degeneration that causes progressive vision loss usually to the point of legal blindness. The progression usually starts between the ages of six and twelve years old and plateaus shortly after rapid reduction in visual acuity.

Genetics
It can be associated with several different genes:


 * STGD1: The most common form of Stargardt disease is the recessive form caused by mutations in the ABCA4 gene. It can also be associated with CNGB3.


 * STGD3: There is also a rare dominant form of Stargardt disease caused by mutations in the ELOVL4 gene.


 * STGD4: Associated with PROM1.

The classification "STGD2" is no longer used.

Stargardt disease is the most common form of inherited juvenile macular degeneration.

Presentation
Those with Stargardt disease are sensitive to glare; overcast days offer some relief. Vision is most noticeably impaired when the macula (center of retina and focus of vision) is damaged, leaving peripheral vision more intact. Symptoms usually appear before age 20. Symptoms include wavy vision, blind spots, blurriness, impaired color vision, and difficulty adapting to dim lighting.

Some patients are able to drive. Many patients use magnifiers to help them see, and wear sunglasses to slow the development.

Pathophysiology
The genetic defect is manifest in the visual phototransduction cycle. The ATP-binding cassette transporter is defective and leads to a build up of a toxic metabolite lipofuscin.

Management of Stargardt disease
Some doctors have recommended colored lenses that filter out wavelengths shorter than 600 nm; the light wavelengths that stimulate rod vision.

There are no clinical trials to provide evidence for ways in which sufferers can slow the progression of the disease. Therefore the advice provided is based on theoretical models of the disease, and includes avoiding bright sun light where possible, and wearing a broad brimmed hat and sunglasses where appropriate.

History
The disease was discovered in 1909 by Karl Stargardt, an ophthalmologist in Berlin.

In 1997, it was discovered that mutations in the gene cause Stargardt. The mutations cause the production of a dysfunctional protein that cannot perform energy transport to and from photoreceptor cells in the retina. The photoreceptor cells then degenerate, causing vision loss.

Stem Cell Therapy
On November 22, 2010, it was announced that Advanced Cell Technology received United States Food and Drug Administration clearance to immediately initiate a Phase I/II multicenter clinical trial using retinal cells derived from human embryonic stem cells (hESCs) to treat patients with Stargardt’s Macular Dystrophy. This is the first ever human trials of this nature as an approach to treat Stargardt's Macular Dystrophy.

Notable cases
George W. Bush, in June 2006, teased a reporter named Peter Wallsten who was wearing sunglasses due to Stargardt. The reporter later explained that the President had no way of knowing, and that he was not offended.

Another notable case is US distance runner Marla Runyan, who, in 2000, became the first legally blind athlete to make the US Olympic team. Runyan, who had previously won seven Paralympic medals, finished eighth in the 1,500 meter finals, the top finish by an American.

Also, in September 2008, at the Beijing Paralympics games, Jason Smyth, representing Ireland, won 2 Gold medals, in the 100m and 200m, with Paralympic world record times. He also became the first Paralympian to compete in the European Championships, in 2010, in Barcelona.

In February 2010, Canadian Paralympic cross-country skier Brian McKeever was named to the Canadian Olympic team. The seven-time Paralympic medal winner would have been the first winter athlete to compete in both the Paralympic and Olympic Games. However, on 27 February, days before the end of the Olympics, McKeever was omitted from the team when Canada chose four other athletes to replace him, who historically have better times than McKeever.