Treatment - Usher Syndrome
While researchers are gaining new understandings about the precise genetic causes of Usher syndrome and the actual mechanisms of the disease, research has not yet found a way to halt the degeneration of the retina or to restore normal hearing. However, research is continuing in several different areas that can offer hope for people with Usher syndrome.
Possible treatments for Usher syndrome can be categorized by the two sensory organs that are affected:
Cochlear Implant Technology Benefits People with Hearing Loss
One of the outstanding recent scientific accomplishments that has benefited people affected by hearing loss, is the cochlear implant. The cochlear implant is a small electronic device that is surgically implanted in the mastoid bone behind the ear and in the inner ear. The surgeon places the device through an incision that is masked by the ear.
A cochlear implant consists of four parts:
1. microphone that picks up sounds from the environment
2. speech processor that chooses and organizes sounds from the microphone
3. transmitter and receiver stimulator that translates the sounds into electrical impulses
4. series of up to 22 electrodes that transmit the electrical impulses to the auditory nerve
In a normal healthy ear, sound waves travel from the outer ear through the middle ear to the inner ear where they are converted into electrical signals by special sensory cells known as nerve hair cells. The electrical signals are then sent to the brain via the auditory nerve.
In people affected by Usher syndrome (as well as other forms of deafness), the nerve hair cells are dead or deformed. The cochlear implant takes the place of these nerve hair cells by converting sounds into the electrical impulses which trigger the auditory nerve. Although the auditory nerve contains 30,000 individual nerve fibers, it was discovered that only 22 electrodes are needed to transmit speech and common sound patterns to the brain.
The majority of totally deaf patients who receive cochlear implants are able to detect medium to loud sounds, including speech at comfortable listening levels. For many patients, cochlear implants assist in communication by improving their ability to lip-read. In a smaller number of patients, the implant facilitates an understanding of words or sentences without the use of lip-reading. Results vary depending on factors such as age at time of deafness, age at implant surgery, duration of deafness, condition of the remaining auditory nerve fibers, and training.
The technology behind the cochlear implants is rapidly improving. Newer implants are smaller, lighter, and able to resolve a greater variety of sounds. In addition, computer software is now available that simplifies the "programming" of an implant to optimize its efficiency. Further improvements in cochlear implant technology and use can be anticipated as greater experience with the device leads to improvements in design and training to optimize its use.
Scientists have been very encouraged by the results of a six-year clinical study reported in June 1993 concerning vitamin A palmitate and RP. Researchers wanted to determine if increasing the amount of vitamin A palmitate in the diet could slow the progression of retinal degenerations. A carefully designed study showed that taking vitamin A palmitate can slow the progression of retinal degeneration for some people who have RP or Usher syndrome type II.
Subjects in the study included people with several common forms of RP and Usher syndrome type II. Patients with Usher syndrome type I were not studied. Therefore, recommendations cannot be made for those who have Usher syndrome type I. Patients with a daily consumption of about 18,000 International Units (IU) of vitamin A (15,000 IU palmitate in dietary supplements and about 3,000 from their regular diet) were found to have a lower rate of retinal degeneration, as measured by ERG, than patients not taking these doses of vitamin A. Taking vitamin A palmitate did not completely stop retinal degeneration, but the researchers found a 20 percent slower average annual decline of remaining retinal function in people taking the supplement. They concluded that the slowing could mean additional years of useful vision for many people with RP. For example, a person starting the daily supplement at age 32 could expect to retain some useful vision until the age of 70, while a person not taking the supplement would lose useful vision by age 63.
However, there are some warnings that accompany this recommendation. There is no evidence that doses higher than 15,000 IU provide greater benefits, and doses over 25,000 IU daily may be toxic and cause side effects such as liver disease. While there are no reported instances of toxicity in healthy adults taking 15,000 IU of vitamin A palmitate daily, people taking the supplement are advised to have their blood levels of vitamin A measured and have a test of their liver function before they begin the regimen, and annual tests thereafter. Also, because of the potential for birth defects, women who are pregnant or planning to become pregnant are not advised to take vitamin A palmitate in this dosage. This recommendation is for adults; RP patients under the age of 18 were not evaluated and 15,000 IU of supplementary vitamin A palmitate is not recommended for children. Parents of children with Usher syndrome should consult with their eye care professional and pediatrician about therapeutic doses of vitamin A palmitate for children, based on age and body size.
It is important to keep these findings in perspective. Vitamin A palmitate will not cure RP. Taking vitamin A will not improve your vision. The degenerative process will continue, but possibly at a slower rate. People with very advanced RP were not included in this study, and if you have advanced RP you should consult with your eye care professional about the possible benefit of vitamin A palmitate for you.
The same study that found these encouraging results from taking vitamin A palmitate supplements also looked at the effect of vitamin E supplements on retinal degeneration. In the case of vitamin E, the opposite effect was found. People taking 400 IU daily of vitamin E were found to have a faster rate of retinal degeneration than those in the other groups. This led to the recommendation that people with RP should avoid high-dose vitamin E supplements. However, there is no evidence that normal dietary or small supplemental amounts of vitamin E have an adverse effect on the progression of RP.
It is important that people with RP fully understand the implications of the findings regarding vitamin A and retinal degeneration. For a more complete discussion than is possible to include in this booklet (including a source list for this non-prescription supplement in the palmitate form as recommended in the study), contact The Foundation for a brochure, Vitamin A Treatment for Retinitis Pigmentosa.