Definition Near-sightedness is a visual condition where a person is able to see things up close, but not far away.
What is going on in the body? Near-sightedness occurs when light rays entering the front of the eye focus in front of the retina instead of on it. The retina is the membrane in the back of the eye that receives images and carries their signal through the optic nerve to the brain. In most near-sighted people, the light rays don't reach the retina because the eye is too long from front to back. Sometimes the length of the eye is normal but the cornea, the part of the eye that lets in light, is too steep, causing light rays to come together too quickly.
Myopia usually develops in children between the ages of 11 and 13, but can be seen in children much younger. Sometimes the condition does not start until adulthood. Near-sightedness that begins after a person reaches middle age may indicate the start of cataracts. Cataracts are a condition in which the lens, a clear membrane behind the pupil, becomes cloudy.
What are the signs and symptoms of the condition? Symptoms of this condition can include:
blurred distance vision
squinting
rubbing the eyes
headaches
What are the causes and risks of the condition? Myopia is caused by:
an imbalance between the way the cornea and lens bend light rays
an abnormal length of the eyeball
Myopia is probably genetic, although doing a lot of close-up work may contribute to the condition. The theory is that large amounts of close work fattens the lens, causing near-sightedness.
What can be done to prevent the condition? There is no way to prevent near-sightedness or stop its progression.
How is the condition diagnosed? An eye doctor will suspect myopia in a person complaining of blurred vision when reading a blackboard or road signs from a distance. He or she can diagnose this condition during the portion of a routine eye examination called a refraction test.
What are the long-term effects of the condition? People who are very near-sighted are more likely to develop serious eye problems such as:
holes or tears in the retina.
high pressure in the eye, called glaucoma
degeneration in the central portion of the retina, called macular degeneration
cataracts
As they age, these people must be followed more closely by an opthalmologist (eye doctor) to prevent vision loss.
What are the treatments for the condition? Treatment for myopia includes:
glasses
contact lenses
refractive laser surgery
How is the condition monitored? A person who is slightly near-sighted needs to update his or her glasses prescription every 2 to 3 years, or sooner if he or she thinks it is needed. A person who is very near-sighted needs to see an opthalmologist more often to be checked for high pressure in the eye, degeneration in the retina and cataracts.
Author: William Stevens, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
