Juvenile Retinoschisis: Description, Causes and Risk Factors:
Juvenile retinoschisis is an inherited disease diagnosed in childhood that causes progressive loss of central and peripheral (side) vision due to degeneration of the retina.
Juvenile retinoschisis, also known as X-linked retinoschisis, occurs almost exclusively in males. Although the condition begins at birth, symptoms do not typically become apparent until after the age of 10. About half of all patients diagnosed with juvenile retinoschisis first notice a decline in vision. Other early symptoms of the disease include an inability of both eyes to focus on an object (strabismus) and roving, involuntary eye movements (nystagmus).
It is caused by defects in a gene, RS1 (retinoschisin 1), on the X chromosome. Several different changes (mutations) within this gene can cause the disease. Genetic testing can identify the specific mutation within the RS1 gene almost 95% of the time.
Juvenile retinoschisis is genetically passed through families by the X-linked pattern of inheritance. In this type of inheritance, the gene for the disease is located on the X chromosome. Females have two X chromosomes and can carry the disease gene on one of their X chromosomes. Because they have a healthy version of the gene on their other X chromosome, carrier females typically are not affected by X-linked diseases such as juvenile retinoschisis. Sometimes, however, when carrier females are examined, the retina shows minor signs of the disease.
Males have only one X chromosome (paired with one Y chromosome) and are therefore genetically susceptible to X-linked diseases. Males cannot be carriers of X-linked diseases. Males affected with an X-linked disease always pass the gene on the X chromosome to their daughters, who then become carriers. Affected males never pass an X-linked disease gene to their sons because fathers pass the Y chromosome to their sons.
Female carriers have a 50 percent chance (or 1 chance in 2) of passing the X-linked disease gene to their daughters, who become carriers, and a 50 percent chance of passing the gene to their sons, who are then affected by the disease.
Vision loss associated with juvenile retinoschisis is caused by the splitting of the retina into two layers. This retinal splitting most notably affects the macula, the central portion of the retina responsible for fine visual detail and color perception. On examination, the fovea (the center of the macula) has spoke-like streaks. The spaces created by the separated layers are often filled with blisters and ruptured blood vessels that can leak blood into the vitreous body (the transparent, colorless mass of jelly-like material filling the center of the eye). The presence of blood in the vitreous body causes further visual impairment. The vitreous body degenerates and may eventually separate from the retina. The entire retina may also separate from underlying tissue layers causing retinal detachments.
The extent and rate of vision loss vary greatly among patients with juvenile retinoschisis. Central vision is almost always affected. Peripheral (side) vision loss occurs in about half of all cases. Some patients retain useful vision well into adulthood, while others experience a rapid decline during childhood.
The symptoms of juvenile retinoschisis are usually noticed about the time that a boy enters public school - although in families where the disease is inherited, and early testing is done, very young children may be diagnosed.
The most common symptoms are a general loss of vision
and difficulty seeing fine detail. Some boys may also have nystagmus
(rapid involuntary movements of the eye from side to side) and strabismus (eyes turned in or cross-eyed). Because of this, sometimes retinoschisis is initially diagnosed incorrectly as amblyopia (lazy eye).
An ophthalmologist may suspect retinoschisis after a simple eye examination, particularly if a wheel-like pattern of splits is visible in the macula. However several tests can clarify and confirm the diagnosis:
ERG (electroretinography) measures the electrical responses of the retina. During this test, a special contact lens is placed on the eye, and the eye is exposed to flashes of light.
- OCT (optical coherence tomography) makes digital images of the retinal layers.
- Genetic testing (starting with a blood sample) can identify the gene defects that cause juvenile retinoschisis.
In 1997, researchers identified mutations in a gene on the X chromosome that cause juvenile retinoschisis. Scientists are now studying the gene to determine its function in the retina. This information will greatly enhance efforts to develop treatments for juvenile retinoschisis.
A recent study showed that a drug called dorzolamide (trade name Trusopt) may improve retinal health and restore some vision in people with retinoschisis.
Individuals with juvenile retinoschisis may also benefit from the use of low-vision aids, including electronic, computer-based and optical aids. Orientation and mobility training, adaptive training skills, job placement and income assistance are available through community resources.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.