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Refractive error Print E-mail

A refractive error is an error in the focusing of light by the eye, a frequent reason for reduced visual acuity, and is categorised in spherical errors (myopia or hyperopia) and cylindrical errors (astigmatism):

Myopia (or nearsightedness) occurs when the eyeball is too long, or the cornea is too steep, so that images are focused before rather than on the retina at the back of the eye. A myopic eye can see clearly up to a certain distance and then objects begin to appear fuzzy.

Hyperopia (or farsightedness) occurs when the eyeball is shorter than normal or the cornea is too flat. As a result, images form after the retina. A hyperopic eye will focus on more distant objects, but close-up objects will appear blurry.

Astigmatism (regular and irregular) is a defect of the eye, where vision is blurred by an irregularly shaped cornea, ellipsoidal instead of spherical. The uneven cornea causes light rays to focus on many points in the eye and distorts both close and far vision and may lead to shadowing, loss of contrast sensitivity, distorsion, blurred vision, and ghosting. Irregular astigmatism is often caused by corneal scars and scattering in the crystalline lens. Regular astigmatism is mainly due to excessive corneal toricity.

Refractive errors are managed depending on the severity of the condition with glasses, contact lenses, refractive surgery, or a combination of the three.

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