Retinitis pigmentosa is an eye disease that occurs rather often in the deaf and hard of hearing. Most often both the hearing loss and the retinal disease are caused by the same inherited disorder that is called Usher syndrome. Deafness or partial hearing loss is present at birth (Usher Type I and II) or develops later (Usher Type III) and retinitis pigmentosa develops its symptoms later. It becomes increasingly difficult to see in twilight and in the dark.
The word retinitis means inflammation of the retina and is actually a wrong name because RP is not an inflammation but a degeneration of the retina. The word pigmentosa comes from the word pigment that means colour substance. The outermost layer of the retina is pigment epithelium with pigment containing cells. Retinitis pigmentosa first affects the pigment epithelium and the rod cells, and later the cone cells and other retinal cells.
Doctors express themselves saying that Usher syndrom is a "combined loss of hearing and vision" because of sensorineural hearing loss and degeneration of the retina. The word syndrome means that the disease affects several organs (eyes and ears) in a typical way. Sensorineural hearing loss means that the damaged cells are the hearing cells of the inner ear. Degeneration of the retina means that retinal cells, rods and cones, die very slowly, the rod cells earlier, the cone cells later. Loss of retinal functions leads to loss of visual field and other changes in vision.
There are other syndromes that cause loss of hearing and vision but they are more rare than is Usher syndrome. It is also possible that a person who lost his/her hearing for another disease later develops retinal disease. Or a person who is visually impaired may develop hearing problem later in life. Not everyone who has hearing problem and retinitis pigmentosa has Usher syndrome.
One of the common symptoms of RP is photophobia, light sensitivity. It is especially important to remember light sensitivity in communication situations. It can be very difficult to see signs and to lipread if one is dazzled. The interpreter should always arrange the ligths so that the person can see as well as only possible. It would be good to have a dark surface behind the interpreter and have the interpreter wear dark clothing. During summer it may be unpleasant to wear a dark blouse. Then it is better to use a dark apron with sleeves and collar if the deaf person is very light sensitive. Some interpreters may not know the importance of good illumination so they need to be reminded about it.
Another thing to consider is how far and where the interpreter should stand or sit in order to be within the limited field of the visually impaired person. We usually call it communication-field. It is the area that the person can see without moving his/her eyes. The interpreter should always know the size of the communication field. Otherwise he/she may use too large signs.
Changes in vision occur in different Usher persons at different ages. This is called individual variation. Night vision deceases first, then color vision and visual field, and later visual acuity. Some Usher-patients have difficulties in balance function (Usher Type I).
Usher syndrom is inherited from both parents. They both have the abnormal gene that is needed to cause the disease. Only some of their children get the disease. Every child either gets it or does not get it. The risk is that about every fourth child will inherit the disease but since every child has the same chance, it is possible that only one child has it or that even all children may have it.
If an Usher individual wants to have children, he or she is likely to have normal children if the partner does not have the RP disorder in his family. The children, however, all are carriers of the abnormal gene.
All Usher individuals should have genetic counseling at school and when planning their family. Knowledge about the genetic mechanisms and risks does not usually affect the decision to get married to someone but it may affect the decision to have children.
Usher children at school
The oldest child with Usher syndrome in a family is often diagnosed first at school age. It is possible to make the diagnosis earlier if there are any symptoms of decreased night vision or visual field (the child starts looking at his feet when going down the stairs). The visual fields can be measured at the age of 5-6 years in many deaf children and easily at the age of of 7-8 years. All children with sensorineural hearing loss are suspect of Usher syndrome until it is proven that no visual changes develop.
Because Usher syndrome may lead to very poor vision at the age of 25-50 years, it is important that these children have the best possible teaching and motivation in learning language skills, both sign language and written language; also spoken language if possible. Good written language is necessary for learning braille if print is no longer seen.
It is much easier to adjust to live with the dual sensory impairment if the child grows up with that knowledge. Many deaf youngsters go throug a really difficult time in their life when they learn about the visual impairment at 16-18 years of age. A good adjustment requires understanding and acceptance by the family, the teachers and the peers. Therefore it is important that all deaf children learn about visual impairments and learn to live with the visually impaired deaf individuals among them.