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Retinitis pigmentosa (RP) is the name given to a group of inherited eye diseases that affect the retina. Retinitis pigmentosa causes the degeneration of photoreceptor cells in the retina. Photoreceptor cells capture and process light helping us to see. As these cells degenerate and die, patients experience progressive vision loss.
There are types of photoreceptor cells: rod cells and cone cells.
are concentrated along the outer perimeter of the retina. Rod cells help us to see images that come into our peripheral or side vision. They also help us to see in dark and dimly lit environments.
are concentrated in the macula, the center of the retina, and allow us to see fine visual detail in the center of our vision. Cone cells also allow us to perceive color.
Together, rods and cones are the cells responsible for converting light into electrical impulses that are transmitted to the brain where “seeing” actually occurs.
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.
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 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.
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