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School of Medicine
Nearsightedness, Farsightedness and Astigmatism
Nearsightedness (myopia) is a very common condition in which the light coming into the eye is not focused properly onto the retina, making it difficult to see objects far away. The condition is usually caused by an elongation of the eyeball that occurs over time. Farsightedness (hyperopia) is the opposite of myopia, and is usually caused by shortening of the eyeball.
Astigmatism is an imperfection of the cornea preventing part of it from focusing light onto the retina. The result is a blurred area within an otherwise clear image. This problem may occur along with either myopia or hyperopia. These frequent conditions are termed "refractive errors."
The common method of measuring vision loss is the Snellen Test Chart, the familiar rows of increasingly smaller letters. Wilmer ophthalmologists also diagnose a decline in vision using refraction and retinoscopy and, when necessary, automated computerized devices.
Wilmer optometrists and ophthalmologists prescribe eyeglasses and contact lenses to compensate for most refractive errors. In addition, newer techniques actually change the curved shape of the cornea, causing it to focus light directly onto the retina, thus producing a clear image. The techniques performed at Wilmer include Automated Lamellar Keratectomy (ALK), Radial Keratotomy (RK), Excimer Laser Photo Refractive Keratectomy (PRK), and LASIK - a combination of ALK and excimer laser surgery currently undergoing investigation. Wilmer physicians participated in the development of the excimer laser, which they have used since 1990. With it, Wilmer physicians can remove a thin layer of the cornea to sculpt its shape to reduce or correct the refractive error. This new technique is approved for persons 18 years of age and older with specified types of nearsightedness.
In RK, the surgeon makes a series of incisions in the cornea, producing a spokelike pattern of cuts that flattens the tissue, causing light to be focused on the retina instead of in front of it. A 10-year, multicenter study of RK found that it safely and effectively reduces a person's dependence on eyeglasses or contact lenses.
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