Stargardt’s disease is a condition that affects the macula, the central region of the retina. It causes blurred sight, sensitivity to glare, and blind spots in the central visual field. The symptoms usually develop between the ages of eight to twenty years of age and it can be difficult to diagnose this condition in the early stages of the disease. Specialized electrodiagnostic tests may be required to make the diagnosis.
The symptoms of Stargardt’s disease are progressive until the visual acuity reaches 20/200 to 20/400. It is an inherited condition that affects males and females equally, and there is no predilection for any ethnicity. Patients with Stargardt’s do not completely lose their vision, and they respond extremely well to low vision aids. However, it is always best to recognize the problem as soon as it appears, and parents should pay particular attention to the way their children behave and read from the television screens or their textbooks. If the disease is discovered early on, the chances of a successful treatment will be much higher, and Stargardt’s will not leave any emotional or social consequences.
The retina is the light-sensing tissue of the eye that is responsible for vision. It consists of millions of cells that absorb light and send information to the visual centers of the brain. The centermost region of the retina is called the macula and consists of light receptor cells called cone cells. The cone cells provide detailed sight, color vision, contrast vision, and daylight vision. The macula comprises less than 10 percent of the entire retina and is analogous to a “bull’s eye” in a dartboard. Surrounding the macula are rod cells, which extend to the outer peripheral edges of the retina. The rod cells are responsible for night vision, peripheral vision, and provide the brain with information that helps with orientation and mobility.
Stargardt’s disease primarily affects the cone cells of the macula, causing blurred sight, sensitivity to bright light and reduced contrast vision. In the early stages of the disease, children may have difficulty reading the chalkboard and their grades may suddenly suffer. Squinting the eyes, sitting closer to the television, or holding their reading material close to their eyes are also common symptoms. Their visual acuity may measure 20/40 (able to read a 1-inch letter from 20 feet). As the disease progresses, the visual acuity may rapidly deteriorate to 20/200 (able to read a 4-inch letter from 20 feet).
Fortunately, the sight does not change much after this point. Adults with Stargardt’s disease may have blind spots in their central vision, and they may also have difficulty discerning colors. In some ways, it is also fortunate that Stargardt’s only affects the central region of the retina and patients have excellent peripheral vision and do not become totally blind. They can still perform a lot of activities, and the quality of life for these patients will not suffer a damaging blow.
Stargardt’s has been linked to a defect on a gene called ABC-R, which is responsible for providing the cone cells with energy. The reduced function of the gene affects metabolic processes, which eventually lead to the death of the cone cells. The defective gene is inherited in an autosomal recessive manner, which suggests that both parents must be carriers of the defective gene and their children have a 25 percent probability of inheriting the condition. There is no medical treatment to reverse the damage caused by this gene at present. However, scientists and doctors are performing extensive studies on the subject, and hopefully – the results of these research efforts will eliminate the problem once and for all.
Patients with Stargardt’s respond extremely well to low vision aids. Because this disease only affects the central region of the retina, visual aids can displace the image on the healthy areas of the retina. Specialized glasses, bioptic telescopes, filters, and computer technology are extremely helpful in improving the sight of those with Stargardt’s disease. Most students with Stargardt’s can access print visually, and adults frequently can meet the visual criteria for driving when they wear specialized low vision spectacles. In other words, this health condition does not affect the quality of life in such a detrimental way as it may seem from the rest of this article, but it is an inconvenient and unpleasant health condition nevertheless.
A consultation with a low vision specialist and low vision aids are recommended. Low vision aids such as bioptic glasses, handheld telescopes, and video magnification systems can improve distance sight to 20/20 while specialized reading glasses, hand magnifiers, and closed circuit televisions can allow patients to read the small print.
Patients should be evaluated for photochromic spectacles that may improve the clarity of sight, protect the eyes from the harmful rays of the sun, and reduce problems with glare. Photochromic spectacles will turn dark when exposed to sunlight and remain clear when indoors or during the evening.
Tinted contact lenses, specialized melanin filters, and the use of a hat with a dark brim can significantly improve visual function during the day for patients who are severely sensitive to glare and bright light.
Students with Stargardt’s disease will benefit from being positioned in the front portion of the class with their backs facing windows, doors, and glare sources. The use of a black chalkboard and bold architecture chalk are generally easier to see than dry erase boards due to the glare created by the whiteboard. If a dry-erase board must be used, it is very helpful only to use bold black dry-erase markers rather than colored markers.
Students will benefit from having copies of material normally written on the board or presented on overhead transparencies. If PowerPoint presentations are used, a dark background with white letters typed in Arial or Tahoma fonts will improve readability for students with low vision.
Students may have some difficulty seeing small objects such as a baseball while standing in the outfield. They may also have difficulty seeing in the direct sunlight and may prefer to wear their sunglasses and a hat. Students will benefit from additional time to adapt to the indoor lighting after entering the classroom from lunch or recess. Sports such as soccer, basketball, gymnastics, swimming, and golf may be easier to participate in rather than baseball or tennis.
Computer users will benefit from changing the background of the display to a black or blue background with white letters. Enlargement of the font size will also increase readability. For information on how to modify the computer screen, see “Solutions to Help You Use Your Computer.
Students may benefit from using specialized computer software and technology such as Zoom Text magnification software, scanning programs such as Open Book and Kurzweil, and Video Magnification systems. For more information, see Computer and Assistive Technology.
Teenagers with Stargardt’s who are interested in learning whether they have sufficient vision for driving should have a low vision examination by an optometrist who specializes in fitting bioptic driving glasses.
Children with Stargardt’s must be assured that they are not going “totally blind” and will benefit from speaking with a counselor.
Specific low vision aids that are often helpful to patients with Stargardt’s include:
4x to 6x bioptic spectacles, including the Ocutech Autofocus and Designs for Vision Expanded Field Telescope.
DVI clear image aspheric reading glasses
Prescription CPF, Transitions, Melanin, and NoIR filters
3x to 6x aspheric hand magnifiers for reading fine print
Video magnification systems can significantly increase the speed of reading and finishing the homework.
ZoomText magnification software can be extremely helpful to those who perform computer work.