Myopia is the most common eye disorder in the world, and it's a leading cause of visual impairment. It's characterized by an elongated eyeball, in which light is focused in front of the retina instead of on it, causing images to look blurry. The longer the eyeball is, the farther away the retina will be from the point at which the light is focused and the less clarity visual images will have.
People with myopia have trouble seeing objects-
chalkboards, street signs, faces, and pretty much everything else-at a distance. The word “distance” may be misleading, though. Someone with severe myopia may not even be able to make out the time on her wristwatch without putting on her glasses or holding her wrist within inches of her face.
Myopic people tend to squint in an effort to focus light better. This can cause eye strain, fatigue, and headaches.
Environmental influences such as near work, stress, nutrition, and general health may play a small role in whether you develop myopia, but risk factors tend to have been hard-wired into your genetic material at conception. Myopia develops during the elementary school years and usually levels out by about age 20. Men and women are affected in equal numbers.
People with a marked degree of myopia do tend to develop glaucoma more frequently than other people, and they're more likely to have retinal detachments because the oblong shape of the eye puts greater stress on the periphery (edges) of the retina In addition, retinal degeneration is more common among people with myopia. It's especially important, then, for them to educate themselves about these conditions and to have regular comprehensive dilated eye examinations that include measurement of eye pressure and use of other glaucoma screening tools.
Your vision care provider uses a simple visual acuity test and refraction testing to diagnose myopia.
- Visual acuity testing. Most of us are familiar with the “big E” eye chart, so named for the large block letter that usually appears at the top. Eye care professionals know it as the Snellen eye chart, named for the ophthalmologist who invented it in 1863. Using this visual acuity chart, your provider measures how well you see at various distances.
- Refraction testing. Refraction testing is the process of measuring how the eye focuses light. It's done with the aid of a phoropter, a specialized instrument that consists of a jumbo-size pair of goggles hanging from a boom. The goggles conceal a series of lenses that your vision care provider adjusts as you read the letters on a projection screen, choosing stronger and stronger lenses until the letters look crisp.
As part of a comprehensive examination, your provider might also measure fluid pressure in your eyes and dilate your pupils to check the health of the internal structures of the eye.
Myopia is expressed in diopters, a measure of refraction, or the power of a lens to bend light. Myopia is indicated by a negative sign before the number, whereas hyperopia (farsightedness) is indicated by a positive number (see Hyperopia). The farther away from zero the number is, the more myopia you have. If your right eye measures -2.5 diopters and your left eye measures -4.0 diopters, then your left eye is more myopic than your right.
Vision can be corrected with glasses, contact lenses, refractive surgery, or intraocular implants.
- Eyeglasses. Eyeglasses may be a fashion statement for some-
witness Elton John-but most of us just want to keep from mistaking, say, a vacuum cleaner for a crouched intruder in dim lighting. Standard eyeglasses, whether or not they have Dolce & Gabanna frames, do a swell job of correcting vision for most people with myopia.
- Contact lenses. Rigid or soft contact lenses are also effective in correcting myopia. For people who have myopia with astigmatism, toric lenses-
soft contacts with two powers in them, like bifocals-may be a good option (see Astigmatism).
- Refractive surgery. The goal of refractive surgery is to reshape the cornea as an alternative to wearing contacts or glasses. Methods of refractive surgery include various laser procedures, such as LASIK surgery and photorefractive keratectomy (PRK).
- Orthokeratology. Orthokeratology uses a series of specially fitted rigid contact lenses, worn while you sleep, to reshape the corneas. This procedure is attractive to athletes and others who don't want to wear contact lenses during the day. The process can be used to treat myopia of up to -6 diopters, with astigmatism of up to -1.75 diopters. The downside is that retainer lenses must be worn at night every few days, or the eyes will gradually return to their previous curvature.
Of course, if you choose a surgical option, you can still wear glasses as a fashion accessory. But please—no masking tape on the nose bridge. That just wouldn’t be cool.