Usher syndrome is a genetic disorder characterized by early hearing loss, gradual vision loss from Retinitis Pigmentosa, and in certain instances balance issues. Usher syndrome is the most common genetic cause of combined deaf blindness.
Deafness or hearing loss in Usher syndrome is caused by abnormal development of hair cells (sound receptor cells) in the inner ear which causes sensorineural hearing loss. In Usher syndrome type 1, hair cells in the vestibular portion of the inner ear are also damaged, resulting in balance problems.
Loss of vision in Usher syndrome is caused by an eye disease called Retinitis Pigmentosa, which affects the layer of light-sensitive tissue at the back of the eye. Vision loss occurs as the light-sensing cells (called rods and cones) of the retina gradually deteriorate. Night vision loss begins first, followed by blind spots that develop in the peripheral vision. Over time, these blind spots enlarge and merge to produce tunnel vision. See the picture below for an example. In some cases, vision is further impaired by clouding of the eye lens; however, many people with Retinitis Pigmentosa retain some central vision throughout their lives.
Early hearing loss can be detected and diagnosed with standard audiologic testing, which determines what frequency of sounds a child can hear, and how loud the sounds at these frequencies must be before they are audible.
Hearing loss in Usher syndrome cannot be reversed; however children diagnosed today are often treated with cochlear implants. These devices stimulate the nerves of the inner ear directly, mimicking natural hearing. If hearing is less severely affected, hearing aids can be used.
Promising research and genetic testing are currently being conducted. Once such body of research is being conducted by The University of Iowa Institute for Vision Research (UI-IVR), which focuses on eye diseases that are underfunded because of their rarity. One of Saving Sight and Sound’s missions is to raise funds to support UI-IVR, as the Institute is developing treatment for all forms of genetic blindness, including Usher syndrome. UI-IVR has also developed Project Usher, which aims to identify as many people as possible in the U.S. affected by Usher Syndrome, and offer them genetic testing on a nonprofit basis. Lastly, the UI-IVR is currently conducting a $10M matching campaign to develop gene and stem-cell based treatments for Usher syndrome, in which each dollar donated to the UI-IVR through 2020 will be matched by institutional donors, up to $10M dollars. To learn more about UI-IVR and the Usher Challenge, click here.
There are three different clinical types of Usher syndrome. They are called Usher syndrome type 1 (USH1), Usher syndrome type 2 (USH2), and Usher syndrome type 3 (USH3). The table below outlines their clinical characteristics.
|Type 1||Type 2||Type 3|
|Hearing||Severe deafness in both ears from birth||Moderate to severe hearing loss from birth usually in higher frequencies||No hearing loss at birth but slow loss of hearing starting in childhood or teens|
|Vision||Slow vision loss starts with loss of night vision usually in childhood||Slow vision loss starts with loss of night vision in late childhood or teens||Timing and severity of vision loss vary, but most often night vision loss begins in teens|
|Balance||Balance problems from birth||No balance problems||Minimal/no balance problems at birth, symptoms may get worse with age|