剑桥医学英语 Lesson 19-Supplementary Text (Refractive Errors)

Refractive Errors

Refractive error, also known as refraction error, is a problem with focusing light accurately on the retina due to the shape of the eye and or cornea.   The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. 

Near-sightedness results in far away objects being blurry, far-sightedness and presbyopia result in close objects being blurry, and astigmatism causes objects to appear stretched out or blurry. Other symptoms may include double vision, headaches, and eye strain.

There is evidence to suggest genetic predilection for refractive error. Individuals that have parents with certain refractive errors are more likely to have similar refractive errors. Environment, socioeconomic status and higher levels of education have also been reported to be risk factors for refractive error.

The diagnosis of a refractive error is usually confirmed by an eye care professional during an eye examination using a large number of lenses of different optical powers, and often a retinoscope to measure objectively  in which the person views a distant spot while the clinician changes the lenses held before the person’s eye  and watches the pattern of reflection of a small light shone on the eye.

Refractive error is corrected with eyeglasses, contact lenses, or surgery. Eyeglasses are the easiest and safest method of correction.  Contact lenses can provide a wider field of vision; however they are associated with a risk of infection. Refractive surgery permanently changes the shape of the cornea.