The Dr. Bill Takeshita Foundation

Last Modified: Sat, 18 Aug 2007

View other Common Causes of Vision Impairment

Retinitis pigmentosa (RP) describes a variety of eye conditions that affect the cells of the retina causing night blindness, reduced peripheral vision, sensitivity to glare, and blurred sight. It is a genetic condition that can be inherited in various forms of transmittance but there are also many spontaneous cases of RP where there are no family members with this progressive disease. The symptoms of RP most often develop during the teenage years but can develop during infancy or adult life. Unfortunately, there is no medical cure for this disease but advances in biotechnology and genetics are promising. Low vision optometric rehabilitation and vitamin therapy are recommended to enhance the remaining level of vision and slow the progression of the condition.

The retina is the light sensing tissue that lines the internal surface of the eye. It consists of millions of rod cells and cone cells. The cone cells are located in the central region of the retina and are responsible for detailed sight, color vision, and vision during the daylight. In contrast, the rod cells are lined on the periphery of the retina and provide peripheral vision, night vision, and visual clues for walking. RP affects a region of the rod and cone cells called the outer segments. The outer segments tend to accumulate too much metabolic waste, which is normally disposed of. Consequently, the retina appears pigmented with clumps of pigment. As the debris accumulates, the function of the rod and cone cells deteriorates.

The rod cells of the mid-periphery region of the retina are generally the first affected. This tends to cause a “donut shaped” blind spot in which the central vision and extreme peripheral vision are normal. As the disease progresses, the rod cells in the peripheral retina degenerate, causing night blindness and tunnel vision. In the more advanced stages, the cone cells in the center of the retina may also deteriorate and the clarity of sight may become blurred or patients may become totally blind. However, there are many patients with RP who have 20/20 eyesight with very sharp central vision.

Retinitis pigmentosa is often categorized based on its inheritance pattern. Autosomal dominant RP describes cases of RP where there is a strong family history and members of each generation have RP. Autosomal recessive RP describes the inheritance pattern where both parents must have the abnormal gene in order for their children to inherit the condition. In X-linked recessive RP, the abnormal gene is located on the X chromosome and is transmitted from the maternal grandfather to his grandsons. The mothers are carriers of the gene but do not have symptoms. X-linked recessive RP tends to affect boys at a young age and tends to cause significant vision loss by the teenage years. The majority of cases of RP are not as easily identifiable based on inheritance. Many people with RP have no family history of the disease. Simplex RP is the term used to describe cases in which only one person has acquired the abnormal gene. Multiplex describes cases when more than one person in a generation has developed the disease while there are no ancestors with RP.

Patients with RP tend to have many functional problems. Night blindness is the most common symptom of RP. Children and adults may avoid going out at night or have difficulty finding their chairs in dimly lit restaurants or movie theatres. They may have problems adapting to different lighting conditions such as seeing in a store after being outdoors in the bright sunlight. They may also have difficulty finding objects that they drop on the floor or children may have difficulty catching a baseball. In the more advanced stages, they may bump into objects when walking and may trip over steps and curbs.

There is no treatment for RP. Some studies have reported that light may be a contributing factor and Vitamin A Palmitate and Vitamin C may slow the progression of the disease. Low vision rehabilitation is the most beneficial treatment to help children and adults with RP. Specialized filters can protect the eyes from the potentially damaging rays of the sun. These glasses can reduce problems with glare while not being too dark to reduce their vision. Visual field expanders, night vision spectacles, and computer technology can help those with RP to perform daily activities and job responsibilities independently. All patients with RP should receive mobility training to help them learn to walk safely and more independently. Biotechnology may prove to be helpful for patients with RP in the future. Presently, studies are being performed to assess the safety and benefit of the use of stem cell transplantation, sub-retina microchip implantation, and electrical array stimuli to help blind RP patients.

Recommendations

• Children and adults with RP will benefit from a consultation by a low vision specialist and low vision aids. Specialized filters, visual field expanders, and scanning training can be very helpful. Low vision aids such as reverse telescopes, visual field expanders, and reverse bioptic telescopic systems can assist patients with RP to see a wider field of view when walking.
• Students will benefit from being positioned in the middle section of the classroom 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 white board. In the event that a dry erase board must be used, it is very helpful to only use bold black dry erase markers rather than colored markers.
• Tinted paper with bold lines, bold felt pens, and thick pencils will help students to perform writing tasks at school. Students who are bothered by glare will also benefit from placing their paper on a dark blotter or dark piece of construction paper to help them to see the edges of their paper.
• Students with RP and reduced acuity 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 with RP will often have difficulty participating in sports due to their reduced peripheral vision.
• The use of bright ambient illumination will help patients with RP. Thus use of full spectrum fluorescent lighting will illuminate work areas in the kitchen, dining area and bedroom for maximal use of vision. The use of a halogen track light with spot bulbs over the desk will provide ample illumination for reading. For more information, please see Lighting and Vision.
• Consider painting walls an off white color with flat paint to increase the ambient lighting.
• Students will benefit from using a flashlight to help them acclimate to dark environments on field trips to museums.
• 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 only be necessary if the student has reduced clarity. Most students with RP will perform better with smaller print. For information on how to modify the computer screen, see “Solutions to Help You Use Your Computer.
• Computer users with very poor vision may benefit from using computer technology programs that read aloud. Other software programs such as screen readers, magnification programs, and scanning software are recommended. For more information, please see Computers and Assistive Technology.
• All patients with RP should seek counseling by a therapist who is experienced in working with children and adults who are visually impaired.
• Specific low vision aids that are often helpful to patients with RP include:
  • 2.8X reverse telescope for field expansion
  • Night vision spectacles
  • The use of Mini DV Camcorders with night vision mode can improve visual function for mobility at night.
  • Protective and contrast enhancing filters such as the Melanin filter, CPF 527 Design, and the Eagle 400 filter.
  • Aspheric ventricular reading glasses with multiplayer antireflective coating and Trivex lens material.
  • ZoomText 9.0 with speech and JAWS screen reading software programs can be very helpful for computer users with RP. These programs can read text aloud to assist those who perform extensive amounts of reading. Open Book is another excellent program that scans reading materials and reads it aloud.
• For more information, please see Low Vision Rehabilitation