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Refractive error

Refractive errors are thought to occur due to a combination of genetic and environmental factors. Trauma or ocular disorders such as keratoconus may induce refractive errors

Blurry vision may result from any number of conditions not necessarily related to refractive errors. The diagnosis of a refractive error is usually confirmed by an eye care professional during an eye examination using an instrument called a phoropter which contains a large number of lenses of varying optical power.

In combination with a retinoscope (a procedure entitled retinoscopy), the doctor instructs the patient to view an eye chart while he or she changes the lenses within the phoropter to objectively estimate the amount of refractive error the patient may possess. Once the doctor arrives at an estimate, he or she typically shows the patient lenses of progressively higher or weaker powers in a process known as refraction or refractometry.

Cycloplegic agents are frequently used to more accurately determine the amount of refractive error, particularly in children An automated refractor is an instrument that is sometimes used in place of retinoscopy to objectively estimate a person's refractive error. Vision defects caused by refractive error can be distinguished from other problems using a pinhole occluder, which will improve vision only in the case of refractive error.

How refractive errors are treated or managed depends upon the amount and severity of the condition. Those who possess mild amounts of refractive error may elect to leave the condition uncorrected, particular if the patient is asymptomatic. For those who are symptomatic, glasses, contact lenses, refractive surgery, or a combination of the three are typically used.

In the case of myopia, however, some people believe that such treatments may also have the long-term effect of exacerbating that refractive error i.e., making the patient even more nearsighted. This would be due to the very same prescription that is tailored for use at a 12-to-20-foot distance also commonly being used for close-up work as well, thus artificially amplifying the focusing stress that would normally be presented to the accommodation mechanisms of the eye at that distance.[citation needed] However, this exacerbating effect is not generally believed to exist in the general case, although in cases where the myopia is due to accommodative spasm, removing the corrective lenses for a time may lead to improvement.


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