There are some individuals in this world, who are born with hearing impairment or visual impairment. Such people have a dark and silent world of their own. There are others who are born fine but after certain time due to various factors, their vision diminishes. People suffering from Usher syndrome are one of those unfortunate ones who gradually lose their vision. Usher syndrome is the most common condition that involves both hearing and vision problems. A syndrome is a disease or disorder that has more than one feature or symptom. The major symptoms of Usher syndrome are hearing impairment and retinitis pigmentosa, an eye disorder that causes a person's vision to worsen over time (Usher 1914). Some people with Usher syndrome also have balance problems. Von Graefe, in 1858, (Hess-Rover et al, 1999) was the first to describe the concurrence of deafness and retinitis pigmentosa. However, the syndrome was named after Charles Usher, who was a British ophthalmologist, who believed that the condition was inherited or passed from parents to their children. Approximately 3 to 6 percent of all deaf children and perhaps another 3 to 6 percent of hard-of-hearing children have Usher syndrome. In developed countries such as the United States, about 4 babies in every 100,000 births have Usher syndrome (NIDCD Report, 2005).
II CAUSESAND SUBTYPES:
Usher syndrome is an inherited syndrome that is passed from parents to their children through their genes. Genes are located in every cell of the body, except for red blood cells, which don't have a nucleus (Zanden, 2003). Genes play an important role in giving traits to an individual. Genes are inherited characteristics that are responsible for the hair color, skin color and for the development and progress of various body parts. Each person inherits two copies of each gene, one from each parent (Zanden, 2003). Sometimes genes are altered or mutated. Mutated genes may cause cells to act differently than expected (Zanden, 2003). People suffering from Usher syndrome have these mutated genes which cause their disability. There are three types of Usher syndrome. 1)Usher syndrome type 1
2)Usher syndrome type 2
3)Usher syndrome type 3
Type 1 and 2 are the most common types of Usher syndrome. Type 1 is known as an autosomal recessive disorder. Children who suffer from this syndrome are profoundly deaf from birth and have severe balance problems (Vernon, 1969; Vernon & Hicks, 1983). Some of the children obtain little or no benefit from hearing aids. Most of these children use sign language to communicate with one another. Children who suffer from balance problems are slow to sit without support and rarely learn to walk before they are 18 months old. These children usually begin to develop vision problems by the time they are ten. Visual problems most often begin with difficulty seeing at night, but tend to progress rapidly until the individual is completely blind (Vernon, 1969) In type 2, Children are born with moderate to severe hearing impairment and undergo the progressive loss of vision from adolescence onward (Kimberling & Moller, 1995). Children suffer from blind spots that begin to appear shortly after the teenage years. Of persons who are deaf-blind, perhaps 50 percent have Usher syndrome (Smith et al., 1994). Children born with type 3 have normal hearing and normal to near-normal balance....