Vision loss and Usher syndrome
The eye condition associated with Usher syndrome is called retinitis pigmentosa (RP). It is a condition that affects the retina
About the retina
The retina is a thin piece of light-sensitive tissue made up of layers at the back of the eye. The lens, at the front of the eye, focuses light on to the retina. The result of RP is the gradual deterioration of the light-sensitive cells of the retina, known as photoreceptors. There are two kinds of photoreceptors – rods and cones. Rod photoreceptor deterioration is the most commonly encountered problem in RP.
RP is progressive and begins at the edges of the retina, when the rod cells begin to deteriorate. This means that the sensory cells that were responsible for function in dim lighting are no longer working properly, reducing an individual’s ability to see in poorly lit environments. This often exhibits within the first decade of life of a child with Usher type 1 and the second decade of life of a child with Usher type 2. In the case of Usher type 3, the onset of night blindness varies and is generally thought to occur later in life.
The deterioration of the rod cells then progresses to cause tunnel vision, meaning that individuals' vision is restricted to what is directly in front of them.
The rate of RP degeneration varies between individuals, even siblings and other family members, with Usher. Over time, the cone photoreceptors in the retina also deteriorate, causing further restrictions to vision, reduced perception of fine detail and colour blindness.
However, many people with Usher will retain a very small amount of useful vision into middle age. While there is no treatment for RP currently generally available, there are a number of potential future treatments undergoing clinical trials.
Individuals with night blindness, prior to a diagnosis, may fear being in the dark e.g. walking or driving home at night. With the addition of tunnel vision developing, individuals may appear to others and themselves as clumsy as they may often bump into objects that are present in their peripheral vision but are unable to see it. It is only once a diagnosis is made that these events might begin to make sense to the individual and others concerned.
Individuals, prior to the diagnosis of RP and Usher, may have already discovered and adapted to their hearing loss via learning British Sign Language (BSL) or lip reading, possibly in addition to hearing aids or cochlear implants. As their RP progresses, communication may become more difficult. For example, BSL may become restricted to a visual frame that fits the individual’s visual field.
In the relatively rare cases whereby individuals have developed another eye condition affecting their remaining sight or their RP has progressed to the point where they can no longer rely on vision for communication, individuals may learn to communicate via tactile signing. This is why routine check-ups at the eye clinic are important; specialists can monitor the progression of RP as well as detect potentially treatable complications such as the development of cataracts.
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Created: February 2016
Review due: February 2018
First published: Wednesday 2 December 2015
Updated: Friday 5 February 2016