Myopia (Nearsighted)

Myopia is the medical term for nearsightedness. Nearsighted eyes are good at seeing objects that are close up but have trouble seeing objects that are far away.  This is due to a refractive error in the eye. Refraction is the bending of light. When a light wave enters the eye, it is bent by the cornea as it makes its way through to land on the retina.  There are two different factors that can contribute to myopia: the curvature of the cornea and the length of the eye.  If the curvature of the cornea is too great, the light beam lands on the wrong part of the eye.  Similarly, if the length of the eye is too long, the light will land in front of instead of on top of the retina.  Either way, the result is that far away objects become blurry and out of focus.  Myopia is an eye disorder, not a disease.  Because of the role refraction plays in this type of nearsightedness, myopia is known as a refractive disorder.

Causes
Myopia is often inherited from the parents. Chances are, if your parents wore glasses, you will need glasses too.

Onset and Treatment
The first signs of myopia often become noticeable when a child has a difficult time reading a chalkboard or seeing the teacher clearly but has no trouble reading his textbook. Other signs are the decreased clarity of a distant TV screen, problems driving at night or blurred vision at the movies.  Squinting is an outward sign that a child may need to be examined for myopia. They might also sit closer to the television, rub their eyes frequently or hold a book very close to their face. A child may be too embarrassed to complain of vision problems or they might be unaware of the changes in their vision, emphasizing the need for regular eye exams for children. Common options for treatment are the use of glasses or contact lenses.

Diagnosis
A diagnosis of myopia can be made by taking a classic vision test.  A person who is nearsighted will have an easy time reading the letters on a Jaeger eye chart (the close objects chart) but a hard time with a Snellen chart (the far objects chart). If a problem in the patient’s vision is detected during the eye chart test, the retina may be examined using a retinoscope. This device shines light on the patient’s retina so the doctor can examine it and find the issue causing problems with the patient’s vision. When other causes of nearsightedness, such as eye disease, are ruled out and the problem with vision is determined to be a refractive error, the doctor will us a phoropter. This is the machine that allows the doctor to show a series of lenses to a patient, switching back and forth between them to determine the best fit for corrective lenses.

Risks
People with myopia are at a higher risk for glaucoma and cataracts. They also have a higher than average chance of having a detached retina. If you notice a sudden change in vision, a loss of central vision, a large increase in the amount of floaters (squiggly, transparent shapes that “float” across the eye), or sense a feeling of heaviness in one eye, this could be a sign of a detached retina.  Immediately seek treatment from a medical professional.

Prevention
There are no proven methods for preventing myopia. There are some studies being done that show children who spend more time outdoors in the sun develop myopia at a slower rate. Because of the known ties between close work and myopia, it is best to limit the amount of time children spend close to a screen and make sure that any areas where close work is performed, such as a desk or computer station, are well-lit.  Give your eyes a break.  Take frequent “eye rests” by staring into the distance about every 10 minutes or so for about 30 seconds when performing close work. This action may also help prevent eye strain.