Nearsightedness (or Myopia)

Nearsightedness, or myopia, is the most common refractive error of the eye, and it has become more prevalent in recent years. In fact, a recent study by the National Eye Institute (NEI) shows the prevalence of myopia grew from 25 percent of the U.S. population (ages 12 to 54) in 1971-1972 to a whopping 41.6 percent in 1999-2004.

What Causes Myopia?

Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. Nearsightedness also can be caused by the cornea and/or lens being too curved for the length of the eyeball. In some cases, myopia is due to a combination of these factors. Myopia typically begins in childhood and you may have a higher risk if your parents are nearsighted. In most cases, nearsightedness stabilizes in early adulthood but sometimes it continues to progress with age.


How does nearsightedness affects vision

ΜυωπίαIf you have myopia, you have trouble seeing things far away, but you can see nearby things clearly. This is why myopia is commonly called nearsightedness.
If you can see well enough to read what’s on your laptop or in a book, but you struggle to see what’s on the television or a movie screen, you may be nearsighted. Sometimes people with undiagnosed myopia will have headaches and eyestrain from struggling to clearly see things in the distance.

How is your vision when you are nearsighted

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Why does the eyeball grow too long?

What causes the eyeball to grow too long isn’t completely known, but researchers are exploring a number of factors. For many people, myopia appears to be an inherited condition – in other words, if you have a parent with myopia you are at higher risk for developing it. Researchers are also looking at the effects of sex, age, ethnicity, and environmental exposures – such as sunlight and the amount of time spent doing close-up work – on the development of myopia.
More recently, scientists have been considering the influence of circadian rhythms (sometimes referred to as our biological or body clock), which regulate systems in the body according to the daily cycles of light and dark, as a factor in the development of myopia.


How is myopia diagnosed?

An eye care professional can diagnose myopia during an eye exam, which usually begins with a visual acuity test. This test uses a standardized chart or card with rows of letters that decrease in size from top to bottom. Covering one eye, you will be asked to read out loud the smallest line of letters that you can see. When done, you will test the other eye. If the vision test shows that you are nearsighted, your doctor will use a retinoscope to shine light into your eyes and observe the reflection off the retina to determine the amount of refractive error you have.



What kinds of treatments are available for myopia?

The most common way to treat myopia is to prescribe eyeglasses or contact lenses. Refractive surgery, once the eyes have stopped growing, has become another option for many people.

To find out the amount of myopia you have, an eye care professional uses a device called a phoropter to place a series of lenses in front of your eyes until you are seeing clearly. The combination of the results from both eyes is written as a prescription that will correct your vision to make it as normal as possible.

Eyeglasses use curved lenses to refocus light rays onto the retina, instead of in front of it.

Contact lenses correct vision in the same way as eyeglasses, except they rest directly on the eye.

Refractive surgery changes the shape of the cornea to correct myopia. There are different types of refractive surgery, but the most common are LASIK and PRK.

LASIK removes tissue from the inner layers of the cornea. To do this, a section of the outer corneal surface is cut and folded back to expose the inner cornea. A laser removes a precise amount of tissue to reshape the cornea and then the flap of outer tissue is placed back in position to heal. The correction possible with LASIK is limited by the amount of corneal tissue that can be safely removed.

PRK removes a thin layer of tissue from the surface of the cornea to change its shape. This allows light to focus more accurately on the retina. Like LASIK surgery, with PRK there is a limit to how much tissue can safely be removed and the amount of nearsightedness that can be corrected.

Many people will experience dry eye symptoms after refractive surgery and a small number may develop chronic dry eye syndrome. Some people may also develop vision symptoms such as double vision/ghosting, starbursts, glare, and halos, especially at night. Ask your eye doctor to discuss with you the risks and benefits of LASIK or PRK surgery before you undergo either procedure.
Phakic intraocular lenses (IOLs) are a new option for people who are very nearsighted or whose corneas are too thin to allow the use of laser procedures such as LASIK and PRK. Phakic lenses are surgically placed inside the eye.

Frames and lenses for myopia.

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