Low Vision Help in Retinitis Pigmentosa
Treating the Problems of Tunnel Vision
Tunnel vision occurs gradually for time in most RP patients. When visual fields fall below 15 to 20 degrees, patient have difficulty in safe mobility. These patients report running into objects, especially open doors. They frequently trip over objects and have difficulty going down stairs. Reverse telescopes: These small telescopes are mounted in the top of the patient’s eyewear. When the patient approaches a doorway, a tip of the head allows the patient a wider view. This is accomplished by minifying the area in front of the patient inside the patient’s remaining field of view. This is much like looking backwards through a pair of binoculars. Because the image is smaller, this method works best in patients with relatively good visual acuity, about 20/20 to 20/80.
Bilateral Reverse Telescope View through a minification system.
Field Awareness Systems: These systems use high power prisms to shift the outer field of view inward. The shifting of the field combined with the patients scanning can improve the overall functional field. This method can be used with patients with very poor visual acuity. We can fabricate this system with the Gottlieb Visual Field Awareness System or with press-on lenses. We usually start with a press-on experimentally and may change to a Gottlieb lens if we have a good response. The Gottlieb is much brighter and clearer than the press-on version.
Aiding Night Blindness (Nyctalopia)
Night travel is quite dangerous for many RP patients. The peripheral degeneration causes a loss of the rod cells that are used for night vision. When an RP patient goes outside on a bright moonlight night is can seem to be nearly totally dark outside.Night Vision Scopes: Night vision scopes amplify light. They work on infrared light or heat waves. Most of us in the United States have seen these used by soldiers such as during the Gulf War. In fact the systems we often use were originally developed for military purposes. The Night Scope can allow an RP patient to see into the dark. This can aid both mobility and personal safety.
Light and Glare Control is Crucial in RP
The loss of rod cell functioning in the retina of RP patients leads to many light and glare problems. In low light these patients have night blindness. However, in bright light they can experience “white out” glare, which is like when someone with normal vision walks outside after a movie matinee and is overwhelmed by the bright sunlight. Additionally, the loss of contrast leads to the need for amber/yellow/orange filters even in many inside situations. Each patient is unique and the individual needs of a patient often change overtime as the disease advances.
The amber filter above increase contrast for the patient. 508 Variable Tint From Chadwick Optical
We have developed are own series of amber and yellow filter for RP patients. Above is a sample of our 508 VT. This lenses begins as mild amber and darkens in the sunlight. This is manufactured by Chadwick Laboratories. It fits a gap not covered by other amber lenses. Also, it is a plastic filter thus more protective. We often use dark amber and plum fitover sun wear to control outside glare.