Usher Syndrome (cont.)

Because Usher syndrome affects hearing, balance, and vision, diagnosis of the disorder usually includes the evaluation of all three senses. Evaluation of the eyes may include a visual field test to measure a person's peripheral vision, an electroretinogram (ERG) to measure the electrical response of the eye's light-sensitive cells, and a retinal examination to observe the retina and other structures in the back of the eye. A hearing (audiologic) evaluation measures how loud sounds at a range of frequencies need to be before a person can hear them. An electronystagmogram (ENG) measures involuntary eye movements that could signify a balance problem.

Early diagnosis of Usher syndrome is very important. The earlier that parents know if their child has Usher syndrome, the sooner that child can begin special educational training programs to manage the loss of hearing and vision.

So far, 11 genetic loci (a segment of chromosome on which a certain gene is located) have been found to cause Usher syndrome, and nine genes have been pinpointed that cause the disorder. They are:

• Type 1 Usher syndrome: MY07A, USH1C, CDH23, PCDH15, SANS
  
  
• Type 2 Usher syndrome: USH2A, VLGR1, WHRN
  
  
• Type 3 Usher syndrome: USH3A

With so many possible genes involved in Usher syndrome, genetic tests for the disorder are not conducted on a widespread basis. Diagnosis of Usher syndrome is usually performed through hearing, balance, and vision tests. Genetic testing for a few of the identified genes is clinically available. To learn about laboratories that conduct clinical testing, visit the Web site www.GeneTests.org and search the laboratory directory by typing in the term "Usher syndrome." Genetic testing for additional Usher syndrome genes may be available through clinical research studies. To learn about clinical trials that include genetic testing for Usher syndrome, visit the Web site www.clinicaltrials.gov and type in the search term "Usher syndrome" or "Usher genetic testing."

Source: MedicineNet.com
http://www.medicinenet.com/usher_syndrome/article.htm