Usher syndrome is a condition characterized by partial or total hearing loss and vision loss that worsens over time. Unlike the other forms of Usher syndrome, type II is not associated with vestibular abnormalities that cause difficulties with balance. The degree of hearing loss varies within and among families with this condition, and it may become more severe over time. For example, it is difficult for affected individuals to hear high, soft speech sounds, such as those of the letters d and t. The hearing loss associated with this form of Usher syndrome ranges from mild to severe and mainly affects the ability to hear high-frequency sounds. Usher syndrome type II is characterized by hearing loss from birth and progressive vision loss that begins in adolescence or adulthood. Some people with Usher syndrome type III develop vestibular abnormalities that cause problems with balance. Vision loss caused by retinitis pigmentosa also develops in late childhood or adolescence. By middle age, most affected individuals have profound hearing loss. Hearing loss typically begins during late childhood or adolescence, after the development of speech, and becomes more severe over time. Unlike the other forms of Usher syndrome, type III is usually associated with normal hearing at birth.
People with Usher syndrome type III experience hearing loss and vision loss beginning somewhat later in life.
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