Usher Syndrome (cont.)
How is Usher syndrome diagnosed?
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.
Is genetic testing for Usher syndrome available?
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."
Next: How is Usher syndrome treated? »
- Visual Field Test - Read about visual field testing and vision tests (Amsler grid, Humphrey-Zeiss and Goldman perimetry tests) for glaucoma and macular degeneration detection.
- Genetic Disease - Learn about genetic disease caused by abnormalities in an individual's genome. There are four types of genetic inheritance, single, multifactoral, chromosome abnormalities, and mitochondrial inheritance. Genetic testing is available for some genetic diseases.
- Electroretinography - Read about electroretinography (ERG), an eye test where electrodes placed on the cornea measure electrical responses to light to try to detect abnormal retinal function.
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