|
Myopia, or nearsightedness, is the single most common human eye disease in the world.
Myopia occurs when the eye has grown too long, such that images are focused in the
vitreous inside of the eye rather than on the retina in the back of the eye. The
diagnosis of myopia is made by measuring, in diopters, the strength or optical power
of a corrective lens that focuses distant images on the retina. The degree of
severity of myopia is dependent upon this diopter measurement, with low myopia
described as -3.00 diopters or less, medium/moderate myopia as between -3.00
and -5.00 diopters, and high myopia as -5.00 or more diopters. Approximately 25-30%
of individuals in the United States have myopia, and this figure increases to
70-80% in Asian populations.
High myopia affects up to 2% of the general population in the United States, and
is especially common in Asian populations. High myopia is a major cause of legal
blindness because of its association with an increased risk for premature cataracts,
glaucoma, retinal detachment, and macular degeneration.
// top //
While a number of theories regarding the etiology of myopia exist, it is
most widely believed that myopia is caused by a combination of multiple
genes and multiple environmental factors that work together. Higher-than-
average near-work activities such as reading may be an environmental influence
in producing abnormal eye growth. Additionally, animal models have demonstrated
that myopia can be induced by artificially altering the visual experience early
in life. However, these environmental factors cannot fully explain why so many
individuals within a single family are affected with myopia. Thus, there must
be a strong role that genetic factors play in the development of myopia.
Multiple family studies report a relationship between parental myopia and
myopia in their children. For example, one study of seven year-old children
with myopia found a prevalence of 45% in the family when both parents also
had myopia. Furthermore, children with a family history of myopia have, on
eye exam, changes within the structures of the eye (i.e.: longer eyes measured
by ultrasound) that predispose to myopia even before developing myopia. This
suggests that genes play a large part in the development of the initial shape
and subsequent growth of the eye. Twin studies provide the most compelling
evidence that myopia is inherited. Specifically, there is a greater
relationship between myopia and the related changes in the eye that predispose
to myopia in identical twins than in fraternal twins.
High myopia most commonly appears as a complex disease caused by a combination
of genetic and environmental factors working together. However, it sometimes
presents as one of the features in a wide variety of genetic disorders,
including Stickler syndrome, Marfan syndrome, and chromosome abnormalities
such as Down syndrome.
The Duke Center for Human Genetics and the Department of Ophthalmology at
Duke University Medical Center are currently conducting a genetic study
called "The Molecular Genetics of Myopia" to more specifically determine
the causes of myopia. By studying individuals and families with myopia,
we hope to identify the genes that are involved in eye growth. We hope
this research will allow us to better understand the genetic and environmental
interactions that result in myopia, which may eventually lead to effective
therapies for the severe forms of this potentially blinding eye disease.
// top //
Myopia is the most common eye disorder in the world, although the cause or
mechanism underlying this excessive eye growth is still unclear. It is most
commonly thought of as a complex condition resulting from a combination of
multiple genes and multiple environmental factors that interact together.
The goal of this research is to identify the genes that are involved in eye
growth in individuals and families with myopia. A major step in accomplishing
this goal is to gather information from a large number of families. In
collaboration with other universities in the United States and around the
world, we have enrolled more than 200 families thus far.
One of the common approaches to mapping genes implicated in complex conditions
like myopia is genetic linkage analysis using a whole genome scan. This
approach involves a systematic search of areas along all of the chromosomes
that may contain genes causing or contributing to myopia. Many specific
areas on different chromosomes that are thought to be involved in myopia have
already been identified using this approach. Candidate gene analysis is
another approach used for identifying susceptibility genes of complex eye
diseases. Genes that are expressed in the eye and are located within or
close to the chromosome regions related to high myopia are selected and then
studied by this approach. Our laboratory is using both of these strategies
to identify the genes involved in causing myopia.
// top //
// top //
As Duke CHG researchers continue to define the genetic causes of myopia,
they publish their findings in leading academic journals and share their
knowledge with colleagues at meetings and conferences.
Myopia Research Publications
// top //
The Duke Center for Human Genetics and the Department of Ophthalmology at Duke
University Medical Center are currently recruiting individuals with myopia,
as well as families in which one or more family members have myopia. All
affected individuals must have a history of myopia onset prior to 12 years of
age.
Participation in the research is free and includes complementary parking at
the Duke Eye Center and a limited free eye examination for participating
family members. Each participant will be compensated $15 for his or her time
and travel expenses. Each child providing blood or saliva samples in person
will be given a small token gift for participating in the study.
Study participation includes the following:
-
A telephone interview or interview in person regarding the
participant's medical and family history information
-
An eye examination or clinical information provided by the participant's
eye doctor
-
Obtaining blood or saliva samples from the individual with myopia, his
or her parents and siblings, and other closely related relatives if
possible
-
Permission for the research team to review the medical records of the
individual with myopia to rule out the possibility of a childhood eye
disorder, a history of prematurity, or an underlying genetic syndrome
as an explanation for myopia
If your family is interested in learning more about this research or in
participating, please contact us toll free at (866) DUKE-CHG (1-866-385-3244)
or e-mail myopia@chg.duhs.duke.edu.
// top //
Support Group and Information Resources
MD Support
3600 Blue Ridge Boulevard
Grandview MO 64030
Phone/Fax: (816) 761-7080
Email: director@mdsupport.org
National Eye Institute
Information Office
31 Center Drive MSC 2510
Bethesda, MD 20892-2510
Phone: (301) 496-5248
Email: 2020@nei.nih.gov
National Association for Parents of Children with Visual Impairments
P.O. Box 317
Watertown MA 02471
Phone: (800) 562-6265
Phone: (617) 972-7441
Fax: (617) 972-7444
Email: napvi@perkins.org
National Association for the Visually Handicapped (NAVH)
22 West 21st Street, 6th floor
New York NY 10010
Phone: (888) 205-5951
Phone: (212) 889-3141
Email: navh@navh.org
American Academy of Ophthalmology
P.O. Box 7424
San Francisco CA 94120-7424
Phone: (415) 561-8500
Fax: (415) 561-8533
// top //
|
|
