The Cornea and Refractive Error

Text to Speech

Around 120 million people in the United States wear eyeglasses or contact lenses to correct such conditions as short-sightedness, far-sightedness or astigmatism. These vision disorders are called refractive errors. They affect the cornea and are the most common vision problems in the country.

A refractive error occurs when the curve of the cornea is shaped irregularly. A normal shaped cornea allows incoming light to bend or refract onto the retina with precision. But an irregularly shaped cornea will divert the light away from its intended spot, affecting vision as a result.

If the corneal curve is pronounced, or the eye too long, objects in the distance will appear blurry because the out of shape cornea is refracting the light to focus in front of the retina. This condition is commonly known as short-sightedness or myopia and affects over 25% of adult Americans.

The opposite condition to myopia is far-sightedness or hyperopia. Distance objects will be clear and close-up objects blurry because the out of shape cornea now refracts the light to fall behind the retina.

When astigmatism occurs, the out of shape cornea blurs and distorts near and distant objects. The cornea that produces astigmatism is curved more in one direction than the other, causing incoming light rays to have more than one focal point and falling on different areas of the retina. Between 60 and 70 percent of Americans with myopia also have astigmatism.

Refractive errors are easily corrected with prescription eyeglasses or contact lenses, but refractive surgeries are increasing steadily and becoming a popular option. Please contact your optometrist or ophthalmologist for more advice and guidance.