Myopia

Nearsightedness, or myopia, is a vision problem experienced by up to about one-third of the population. Nearsighted people have difficulty reading highway signs and seeing other objects at a distance, but can see for up-close tasks such as reading or sewing. Nearsighted people often have headaches or eyestrain, and might squint or feel fatigued when driving or playing sports. If you experience these symptoms while wearing your glasses or contact lenses, you may need a comprehensive eye examination as well as a new prescription. Myopia occurs when the eyeball is slightly longer than usual from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. Nearsightedness runs in families and usually appears in childhood. This vision problem may stabilize at a certain point, although sometimes it worsens with age. This is known as myopic creep. Nearsightedness may be corrected with glasses, contact lenses or refractive surgery. Depending on your vision problem, you may need to wear your glasses or contact lenses all the time, or only when you need distance vision, like driving, seeing a chalkboard or watching a movie. If you're nearsighted, your prescription is a negative number. The higher the numeral, the stronger your lenses will be. Refractive surgery can reduce or even eliminate your need for glasses or contacts. The most common procedures are performed with an excimer laser. In photorefractive keratectomy, or PRK, the laser removes a layer of corneal tissue, which flattens the cornea and allows light rays to focus closer to or even on the retina. In laser-assisted in situ keratomileusis (LASIK) — the most common refractive procedure — a flap is cut through the top of the cornea, a laser removes some corneal tissue, and then the flap is dropped back into place. Then there's orthokeratology, a non-surgical procedure where you wear special contact lenses that slowly reshape the cornea over time to correct your myopia. When the lenses are removed, the cornea temporarily retains the new shape, so you can see clearly without the lenses. With orthokeratology or corneal refractive therapy (CRT), an orthokeratology-like procedure approved by the FDA in 2002, you wear cornea-shaping lenses at night, so you have daytime vision without contacts or glasses. Read more about ortho-k and CRT. Another surgical procedure for correcting mild myopia is the implantation of plastic corneal rings, which also alter the shape of the cornea. One advantage of the rings is that they may be removed in case of a problem or adjusted should your prescription change. They can also be left in place permanently. Nearsightedness usually is a mildly debilitating condition that is easily correctible, in most instances with glasses, contacts or vision surgery. But there are rare cases where the myopia is so severe it is considered pathologic. Pathologic, or degenerative, myopia typically develops by age 12 in those with an extraordinarily elongated eyeball. About two percent of Americans are afflicted. The stretching of the eyeball worsens with age, and can result in a progressive and severe loss of vision. Compounding the problem in many cases is an abnormal growth of new blood vessels (neovascularization) beneath the macula.