Retinitis pigmentosa or RP is a disease of the eye which may begin with difficulty seeing at night or diminished peripheral vision. The disease involves damage to the light receptor cells of the retina, at the back of the eye. This genetic and degenerative condition gets progressively worse but does not usually lead to total blindness.
Retinitis Pigmentosa has Genetic Origins
Though it usually appears in childhood, retinitis pigmentosa can occur at any age. It affects about one in 4,000 people. RP can occur by itself, or as part of a broader condition such as Usher syndrome, which includes deafness. Many genetic syndromes have a link to RP.
Affects the Rods and Cones
The basic issue occurring in cases of retinitis pigmentosa is the degeneration of the “rod” cells in the eye, which sit around the outside of the retina and provide low-light vision. Damage to these cells produces worsening night vision and a reduction of peripheral vision. Sometimes, it is the cones in the eye that degenerate first. This more commonly occurs later in the progression of the condition and causes effects such as intense glare and shimmering. People experiencing RP-related vision decline may experience tunnel vision, night blindness, difficulty seeing colors correctly, aversion to bright lights and difficulty adapting when going between bright and dark environments. Total blindness does occur in some instances.
What the Ophthalmologist Sees
In cases of retinitis pigmentosa, an examination of the fundus of the eye, which is standard in routine eye exams, will reveal certain defects. There may be mottling of certain parts of the retina, a waxy appearance to the optic nerve, and shrinking of the blood vessels in the retina. Eye clinics can often take a photograph of the retina to document the progression of the condition.
Tunnel vision, one of the most obvious characteristics of RP in later stages, may not be recognized at first. People with the condition will gradually notice their peripheral vision is not as effective as it used to be. Eventually, these individuals will need to look more directly at their surroundings to see them, rather than relying on their periphery. Eye clinics have a test to determine the extent of a patient’s visual field, which can determine the progression of this symptom.
The Degree and Type of Sight Loss
Retinitis pigmentosa can produce several vision problems. Some patients continue to see with tunnel vision, using special equipment to compensate for the changes. Changes in color vision can affect the ability to notice color-related cues in one’s surroundings, such as pale skin on a sick person or inappropriate colors on spoiled food. Blurry vision limits many activities. Each person’s experience with RP is different, so careful medical examination and help from rehabilitation specialists are essential.
Visual Field Testing
Many people have had visual field testing as part of the screening process for glaucoma, and it is a similar process for mapping the limitations of RP. Typically, the patient will sit in front of a device in which lights flash. As the patient identifies which lights flash, the technician can determine which areas of sight are interrupted.
The electroretinogram or ERG is a device that records retina activity, much like an EKG records heart activity. In this case, after careful preparation, a contact lens-like device is placed on the eye and records retinal electrical impulses when lights are flashed. The results from this test can help the eye doctor understand the light and color response characteristics of the person with retinitis pigmentosa.
There are many ways genetic testing can help a person suspected of having RP. These tests can be helpful in differentiating between retinitis pigmentosa and other conditions that may appear similar at first. Reviewing the results of RP-specific testing can also help determine if the condition is part of a syndrome that could be causing other problems.
A Future Cure for Retinitis Pigmentosa
Some studies show vitamin A may help slow the progress of retinitis pigmentosa. Stem cell therapy and other retinal cell treatments are under study as well, and some show signs of promise. As medical researchers continue to develop treatments for genetic conditions, other options may become available, as well.
In many countries, help for people with limited vision is becoming widely available. In addition to the use of aids such as white canes and service animals, for example, traffic signals are being modified to speak and identify the safe crossing direction, and trains are providing dual whistle sounds to help people locate open doors. There are many devices and software products available for blind and limited-sight users.