An Overview of Usher Syndrome
There are three main types of Usher syndrome called Usher I, II and III. These types are distinguished based on clinical descriptions:
Usher Type I
Usher syndrome type I causes children to be born with severe to profound hearing loss. Individuals with Usher type I often consider themselves to be deaf especially before the advent of cochlear implants. These individuals experience balance (vestibular) problems, which cause them to walk later than average. They usually have problems with night blindness before age 10. Night blindness, as the name implies, means that vision in low lighting is poor; however, it may not be recognized by a child with Usher since it is the only vision the child has experienced. Their vision problems are eventually diagnosed as retinitis pigmentosa (RP). Retinitis pigmentosa is a slowly progressive deterioration of the retina. Peripheral vision is initially affected so individuals have difficulty seeing at the edges of their field of vision. Parents may notice that their children miss steps or bump into walls and mistakenly believe that they are just clumsy.
Usher Type II & III
Individuals who have Usher syndrome type II usually have moderate to severe hearing loss and consider themselves to be hard of hearing rather than deaf. Balance problems are not seen. Retinitis pigmentosa is not typically diagnosed until a child is in his or her teenage years.
Usher syndrome type III is much less common. The symptoms can be quite variable. Hearing loss is often progressive.