Juvenile Retinoschisis

Causes progressive loss of vision

X-linked juvenile retinoschisis is a genetic disorder of the X chromosome. A gene identified as being responsible for juvenile retinoschisis, RS1, encodes an amino acid protein, retinoschisin, which is important in photoreceptor cells of the eye. Physical changes occur in the retina, the part of the eye responsible for vision. The retina splits into two layers, which impairs vision.

Since juvenile retinoschisis is an X-linked recessive disorder, it occurs primarily in boys (since they have only one X chromosome), but it can occur in females with two defective genes (one on each of their two X chromosomes). Juvenile retinoschisis occurs in individuals of all ethnic backgrounds.

Symptoms
Children with juvenile retinoschisis have gradually decreasing vision due to splitting of the retina. Physical changes in the eye may include:

• development of cysts and ruptured blood vessels between the layers of the retina
• holes in the retinal layers, which may lead to detachment of the retina from its underlying tissue (5-22% of individuals)
• leakage of blood into the jelly-like material inside the eye (vitreous hemorrhage)
• changes in the macula, the area of clearest vision in the retina.

Individuals with juvenile retinoschisis may also have difficulty focusing on an object (strabismus) and roving, involuntary eye movements (nystagmus).

Diagnosis
Although juvenile retinoschisis may be diagnosed in infancy, most often it is found in a school-age boy who has failed to pass a school vision screening test. Since the loss of vision is gradual, a child may not be aware that he can’t see well. It is easy to miss the diagnosis in a young child. The extent and rate of vision loss vary greatly.

A thorough ophthalmological evaluation can help distinguish juvenile retinoschisis from similar retinal degenerative diseases such as retinitis pigmentosa. An imaging technique called optical coherence tomography (OCT) provides high-resolution cross-sectional images of the macula to look for abnormalities. OCT can show the changes present in juvenile retinoschisis. An electroretinogram will show dysfunction throughout the retina. Genetic testing can reveal the presence of the defective RS1 gene.

Treatment
No treatment is yet available to stop the progression of juvenile retinoschisis. Surgery can repair vitreous hemorrhage and retinal detachments. Low-vision aids, mobility training, and adaptive training skills can help individuals with vision loss. Genetic counseling can help identify family members who are carriers of the RS1 gene.

Research
Having identified a gene associated with X-linked juvenile retinoschisis, researchers are studying whether gene therapy can be use to replace the defective RS1 gene with an normal version. Experiments with mice have shown promising results. Research foundations such as The Foundation Fighting Blindness are working to identify other genes involved in juvenile retinoschisis and to develop therapies to treat the disease and prevent loss of vision.

Information for this article was taken from:
- The Foundation Fighting Blindness. Juvenile retinoschisis
- Song, M-K. (2005). Juvenile retinoschisis. eMedicine, accessed at http://www.emedicine.com/oph/topic639.htm