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Usher’s Syndrome
Usher syndrome is the most common condition
that affects both hearing and vision. A syndrome
is a disease or disorder that has more than one
feature or symptom. The major symptoms of
Usher syndrome are hearing loss (congenital nerve
deafness) and an eye disorder called retinitis
pigmentosa, or RP. RP causes night-blindness and
a loss of peripheral vision (side vision) through the
progressive degeneration of the retina.
As RP progresses, the field of vision narrows and
a condition known as “tunnel vision”—until only
central vision (the ability to see straight ahead)
remains. Many people with Usher syndrome also
have severe balance problems. About 3-6 percent
of all deaf children and perhaps an equal number
of hard-of-hearing children have Usher Syndrome
(US) which is more then one genetic condition.
What causes Usher’s Syndrome
Usher is inherited and passes from parent to child
through genes. It is an autosomal recessive trait.
The term autosomal means that the mutated gene
is not located on either of the chromosomes that
determine a person’s sex. In other words, both
males and females can have the disorder and can
pass it along to a child. The word recessive means
that, to have Usher syndrome, a person must
receive a mutated form of the Usher syndrome
gene from each parent. If a child has a mutation in
one Usher syndrome gene but the other gene is
normal, he or she is predicted to have normal
vision and hearing. In developed countries such as
the United States, about four babies in every
100,000 births have Usher syndrome.
Retinitis Pigmentosa (RP) affects the sensory cells in
the retina, which is the layer lining the inside of the
eye. The retina itself is made up of several layers of
interconnecting cells, two of which are called rods and
cones. These cells gradually deteriorate and die in RP
and many other so-called retinal dystrophies. The 150
million can see in dim light. Rods are spread
throughout the retina except in the fovea, which is the
spot in the center back directly behind the pupil. The
fovea contains only cones which control day vision
and are important for seeing fine details and color.
Surrounding the fovea is the macula which is rich in
cones, but cones are also scattered throughout the rest
of the retina. About 7 million cones are present in each
retina. By the time the cones deteriorate, doctors can
see distinctive changes when they look at the retina.
These include pigment dispersion, which means that
some parts appear lighter than others, followed by
"bone spicules" which are little jagged spots. The
blood vessels become narrow or "attenuated" and the
optic disc (nerve) develops a pale and waxy yellow
appearance. All of these changes get worse as the
disease progresses.
Sensorineural hearing loss occurs when parts of the
inner ear (including the cochlea and/or auditory nerve)
do not work correctly. The amount (or degree) of
hearing loss can be described by measuring the
hearing threshold (the sound level that a person can
just barely hear) in decibels (dB). The greater a
person's dB hearing level, the louder the sound must
be to just barely be heard. People with Usher’s
syndrome generally have moderate, severe, or
profound depending on the type (I, II, or III)
Diagnosis
Researchers are currently trying to identify all of the
genes that cause Usher’s Syndrome and determine the
function of those genes. This research will lead to
improved genetic counseling and early diagnosis, and
may eventually expand treatment options. 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 lightsensitive cells, and a retinal examination to observe
the retina and other structures in the back of the eye.
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.
Characteristics of the three types:
Type 1
Profound deafness in both
ears from birth
Type2
Type 3
Moderate to severe
hearing loss from birth
Normal at birth progressive loss in
childhood or early teens
Vision
Decreased night vision
before age 10
Decreased night vision
begins in late childhood
or teens
Varies in severity - night
vision problems often begin
in teens
Vestibular
Function
(balance)
Balance problems from birth
Normal
Normal to near-normal
chance of later problems
Hearing
Cassin, B., & Rubin, M. L. (2006). U.
Dictionary Of Eye Terminology 5th
edition (5th ed., p. 271). Gainesville,
FL: Triad Publishing Company (Fl).
Guest, M. (n.d.). Usher's Syndrome & Retinitis
Pigmentosa:Info. & Referrals. A-Z to
Deafblindness. Retrieved July 1, 2010,
from http://www.deafblind.com
Nutting, P. (n.d.). Usher Syndrome Information
on Healthline. Health Search Engine
and Free Medical Information Healthline. Retrieved July 1, 2010,
from
http://healthline.com/galecontent/ushersyndrome-1
Usher's Syndrome. (n.d.). Wikipedia, the free
encyclopedia. Retrieved June 29, 2010,
from http://en.wikipedia.org
Usher Syndrome. (n.d.).
National Institute
on Deafness and Other Communication
Disorders [NIDCD]. Retrieved July 1,
2010, from
http://www.nidcd.nih.gov/health/hearing
/usher.html
Created by: Connie Pester