Usher syndrome is defined as innate reciprocal congenital deafness and progressing loss of vision due to retinitis pigmentosa. Usually the photoreceptors start to degenerate from the outer periphery to the center of the retina including the macula. For the patient the RP is noticeable in the beginning with night blindness (nyctalopia), proceeding into a slow, progressive restriction of the visual field (tunnel vision), which usually leads in a later stage to complete blindness. The hearing impairment with the Usher syndrome is essentially based on a damage of the hair cells in the cochlea of the inner ear.
On the basis of the severity of symptoms, the Usher syndrome was divided into three types: I, II and III. Children with type I syndrome are born profoundly deaf, and eyesight usually begins degrading after the first decade of life, beginning with night-blindness. They also experience degrading tunnel vision. If identified at a young age, children usually receive a cochlear implant, and some then use spoken language. Many use sign language. When vision loss is severe or when one is blind, one must use tactile signing. Problems with balance are present in people with Usher I and sometimes Usher III, due to the failure of the hair cells of the inner ear. Type II children are hard-of-hearing with stable hearing throughout their lives. Changes in sight in type II cases usually begin later, sometimes only becoming noticeable after the second decade of life. In the type III syndrome, hearing loss as well as retinitis pigmentosa can occur later in life. Hearing loss in Usher III is progressive.