CD-ROM Today 1996 January/CD-ROM Today 1996 January.iso/dp/0418/04182.txt

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$Unique_ID{BRK04182}
$Pretitle{}
$Title{Retinoschisis}
$Subject{Retinoschisis Congenital Retinal Cyst Congenital Vascular Veils in
the Retina Giant Cyst of the Retina Vitreoretinal Dystrophy Retinoschisis,
Typical (Blessig Cysts;  Iwanoff Cysts;  Peripheral Cystoid Degeneration of
the Retina) Retinoschisis, Juvenile (Familial Foveal Retinoschisis; Congenital
Retinoschisis) Retinoschisis, Senile Macular Degeneration }
$Volume{}
$Log{}

Copyright (C) 1988, 1989 National Organization for Rare Disorders, Inc.

517:
Retinoschisis

** IMPORTANT **
It is possible the main title of the article (Retinoschisis) is not the
name you expected.  Please check the SYNONYMS listing on the next page to
find alternate names and disorder subdivisions covered by this article.

Synonyms

     Congenital Retinal Cyst
     Congenital Vascular Veils in the Retina
     Giant Cyst of the Retina
     Vitreoretinal Dystrophy

DISORDER SUBDIVISIONS:

     Retinoschisis, Typical (Blessig Cysts;  Iwanoff Cysts;  Peripheral
Cystoid Degeneration of the Retina)
     Retinoschisis, Juvenile (Familial Foveal Retinoschisis; Congenital
Retinoschisis)
     Retinoschisis, Senile

Information on the following disease may be found in the Related
Disorders section of this report:

     Macular Degeneration

General Discussion

** REMINDER **
The information contained in the Rare Disease Database is provided for
educational purposes only.  It should not be used for diagnostic or treatment
purposes.  If you wish to obtain more information about this disorder, please
contact your personal physician and/or the agencies listed in the "Resources"
section of this report.

Retinoschisis means splitting of the eye's retina into two layers.  The
various forms of this disorder can be inherited or acquired.  The disorder is
characterized by a slow progressive loss of parts of the field of vision
corresponding to the areas of the retina which have become split.  Often,
Retinoschisis is associated with the development of saclike blisters (cysts)
in the retina.

Symptoms

Retinoschisis is characterized by splitting of the eye's retina into two
layers, accompanied by the formation of cysts.  The disorder occurs in the
following forms:

Typical Retinoschisis:
This form of the disorder usually occurs among males who are farsighted
(hyperopic).  Frequently, splitting of the retina occurs in both eyes
symmetrically.  Splitting may begin in the lower or upper quarter of the
retina located toward the temples.  Vision is impaired correspondingly.  To
an ophthalmologist looking into the eye with an ophthalmoscope, the lesion
appears as a thin, transparent, veil-like membrane extending up as a dome
into the glass-like inside of the eyeball (vitreous).  This membrane contains
the blood vessels of the retina and often has small white dots (opacities).
Defective vision in bright light (hemeralopia) may also occur.  The
progression of splitting and vision loss often stops for many years.
However, in some cases the progression may occur faster.

Senile Retinoschisis:
This form of the disorder is similar to Typical Retinoschisis but it
usually occurs in older patients, often without apparent symptoms.  Both eyes
are affected in 90% of cases.  Symptoms may develop because of the flowing
together (coalescence) of peripheral sacs (Blessig Cysts;  Iwanoff Cysts).
In the early stage, the cystic space is spanned by thin grey fibers which
gradually break.  This allows the inner and outer leaves of the retina to
separate, forming an elevated cyst.  In Senile Retinoschisis, the split may
extend all the way around the edge of the retina.  However, it does not
usually progress to the back of the retina and may remain unchanged for many
years.

Juvenile Retinoschisis:
This form of the disorder is the most serious type of Retinoschisis.  It
is a slowly progressive genetic disorder occurring among young males.
Splitting of the retina often extends back over the area near the center of
the visual field (macula).  Retinoschisis may affect the center of the macula
(called the "fovea"), which is the area of clearest vision.  In the early
stages, the areas of the retina that are splitting often exhibit large holes
in the anterior leaf between blood vessels, and if breaks develop in both the
front and the back layer of the retina, a true retinal detachment may occur
causing loss of parts of the field of vision.  A completely blind area
(scotoma) with a sharp edge in the area where splitting (schisis) occurs is
evident in the patient's visual field.  The recording of electric impulses
from the eye's retina (electroretinogram; or ERG) shows waves which are
markedly lower than normal, but not obliterated.  Patients with Juvenile
Retinoschisis often have cystic macular degeneration which causes additional
loss of vision.

Causes

Typical Retinoschisis is usually an autosomal dominant genetic disorder.
Senile Retinoschisis is usually an autosomal recessive genetic disorder.
Juvenile Retinoschisis is a sex-linked hereditary disorder.  Acquired cases
of Retinoschisis occur with aging for unknown reasons.

Human traits including the classic genetic diseases, are the product of
the interaction of two genes for that condition, one received from the father
and one from the mother.

In dominant disorders, a single copy of the disease gene (received from
either the mother or father) will be expressed "dominating" the normal gene
and resulting in appearance of the disease.  The risk of transmitting the
disorder from affected parent to offspring is 50% for each pregnancy
regardless of the sex of the resulting child.

In recessive disorders, the condition does not appear unless a person
inherits the same defective gene from each parent.  If one receives one
normal gene and one gene for the disease, the person will be a carrier for
the disease, but usually will show no symptoms.  The risk of transmitting the
disease to the children of a couple, both of whom are carriers for a
recessive disorder, is twenty-five percent.  Fifty percent of their children
will be carriers, but healthy as described above.  Twenty-five percent of
their children will receive both normal genes, one from each parent and will
be genetically normal.

X-linked recessive disorders are conditions which are coded on the X
chromosome.  Females have two X chromosomes, but males have one X chromosome
and one Y chromosome.  Therefore in females, disease traits on the X
chromosome can be masked by the normal gene on the other X chromosome.  Since
males have only one X chromosome, if they inherit a gene for a disease
present on the X, it will be expressed.  Men with X-linked disorders transmit
the gene to all their daughters, who are carriers, but never to their sons.
Women who are carriers of an X-linked disorder have a fifty percent risk of
transmitting the carrier condition to their daughters, and a fifty percent
risk of transmitting the disease to their sons.

Affected Population

Typical Retinoschisis usually occurs in young males who are farsighted.

Senile Retinoschisis usually affects persons in their 50's, 60's or 70's.
It affects males and females in equal numbers.

Juvenile Retinoschisis is a rare disorder, affecting only boys.  However,
there are very rare exceptions which occur when a girl is born to a mother
who is a carrier of the disorder and an affected father.  This form of the
disorder is present at birth, and symptoms progress with time.

Related Disorders

Symptoms of the following disorder may be similar to those of Juvenile
Retinoschisis.  Comparisons may be useful for a differential diagnosis:

Macular Degeneration is a common hereditary disorder of the eye's retina
characterized by a gradual bilateral decrease of vision.  Macular
degeneration can be a static condition for many years but then it becomes
slowly progressive.  An area of impaired vision (central scotoma) within the
visual field, surrounded by a peripheral area of normal vision, is also
symptomatic of this disorder.  A vision disturbance in which shapes seem
distorted or changing (metamorphopsia) can also occur.  (For more information
on this disorder, choose "Macular Degeneration" as your search term in the
Rare Disease Database.)

Therapies:  Standard

Diagnosis of Retinoschisis can be made through various tests:

Measuring visual acuity with the Snellen chart, the patient is asked to
look through a pinhole to determine where on the retina a lesion may exist.

Ultrasonography or ultrasound may show abnormalities when a hemorrhage
has occurred in the eye.

A recording of the electrical impulses emitted by the retina in response
to light stimulus (electroretinogram; ERG) can be made.  These ERG's can
indicate abnormalities of the retina.

A Visual Evoked Response (VER) measures slow electric potentials from the
brain cortex in response to light stimulation.  The VER depends on the
integrity of the entire visual system from the cornea to the occipital part
of the brain's cortex.  The VER is a good objective test to detect the
function of the macular portion of the retina which controls central vision.

Electro-oculography (EOG) is another electrophysiological test to
determine the function of the retina, mainly the nerve cells that respond to
light stimuli (receptors).  A photographic picture made with an
ophthalmoscope of the back portion of the inside of the eyeball (fundus) is
another way to gather information about the retina.  When a child cannot
tolerate the dilation of the eye's pupil and the bright light used for some
of these tests, general anesthesia may be necessary.

Typical and Senile Retinoschisis usually do not require medical
treatment.

In children with Juvenile Retinoschisis, when bleeding occurs within the
eyeball, keeping the eye still helps to settle the blood.  Later, treatment
with laser or cold (cryotherapy) can be applied to close off the damaged area
of the retina.  It is imperative to avoid jarring the head or inflicting
injury to the eye to slow down the degenerative process of Juvenile
Retinoschisis.  With treatment, the person with Juvenile Retinoschisis
usually retains functional vision.

Genetic counseling is recommended for families of children with Juvenile
Retinoschisis.

Therapies:  Investigational

This disease entry is based upon medical information available through June
1988.  Since NORD's resources are limited, it is not possible to keep every
entry in the Rare Disease Database completely current and accurate.  Please
check with the agencies listed in the Resources section for the most current
information about this disorder.

Resources

For more information on Retinoschisis, please contact:

     National Organization for Rare Disorders (NORD)
     P.O. Box 8923
     New Fairfield, CT  06812-1783
     [phone]

     The Association for Macular Diseases
     210 East 64th Street
     New York, NY  10021
     [phone]

     NIH/National Eye Institute
     9000 Rockville Pike
     Bethesda, MD  20892
     [phone]

     National Association for the Parents of the Visually Impaired, Inc.
     (NAPVI)
     P.O. Box 180806
     Austin, TX  78718
     [phone]

     National Association for the Visually Handicapped
     305 East 24th Street
     New York, NY  10010
     [phone]

     Eye Research Institute of Retina Foundation
     20 Staniford Street
     Boston, MA  20114
     [phone]

     Retinitis Pigmentosa Foundation Fighting Blindness
     1401 Mt. Royal Avenue, 4th Floor
     Baltimore, MD  21217
     [phone]
     [phone]

     Vision Foundation, Inc.
     818 Mt. Auburn Street
     Watertown, MA  02172
     [phone]
     [phone]  (within MA)

     American Foundation for the Blind (AFB)
     15 W. 16th St.
     New York, NY  10011
     [phone]
     Regional offices:
     Atlanta, GA  [phone]
     Chicago, IL  [phone]
     Dallas, TX  [phone]
     San Francisco, CA  [phone]

     American Council of the Blind, Inc. (ACB)
     1155 - 15th St., NW, Suite 720
     Washington, D.C.  20005
     [phone]
     [phone]

For genetic information and genetic counseling referrals, please contact:

     March of Dimes Birth Defects Foundation
     1275 Mamaroneck Avenue
     White Plains, NY  10605
     [phone]

     Alliance of Genetic Support Groups
     35 Wisconsin Circle, Suite 440
     Chevy Chase, MD  20815
     (800) 336-GENE
     [phone]

References

MENDELIAN INHERITANCE IN MAN, 7th ed.:  Victor A. McKusick;  Johns Hopkins
University Press, 1986.  Pp. 1236-1237.

DEGENERATIVE RETINOSCHISIS WITH GIANT OUTER LAYER BREAKS AND RETINAL
DETACHMENT:  J.M. Sulonen, et al.; American Journal Ophthalmol (February 15,
1985:  issue 99(2)).  Pp. 114-121.

INDICATIONS FOR VITRECTOMY IN CONGENITAL RETINOSCHISIS:  J. Schulman, et
al.; British Journal Ophthalmol (July 1985:  issue 69(7)).  Pp. 482-486.

X-LINKED RETINOSCHISIS IS CLOSELY LINKED TO DXS41 AND DXS16 BUT NOT
DXS85:  T. Alitalo, et al.; Clin Genet (September 1987:  issue 32(3)).  Pp.
192-195.

VASCULARIZED VITREOUS MEMBRANES IN CONGENITAL RETINOSCHISIS:  D.F.
Arkfeld, et al.; Retina (Spring 1987:  issue 7(1)).  Pp. 20-23.