A short-sighted eve has a new far point of 5.00 m and a near point of 0.25 m. St

Question

A short-sighted eve has a new far point of 5.00 m and a near point of 0.25 m. State the type of lens needed to correct this defect and calculate the power of the lens. Calculate the distance from the lens to the new far point of the eye with the correcting lens in front of the eye. A long-sighted eye has the far point at infinity and a near point which is 40 cm from the eye. State the type of lens needed to correct this defect and calculate the power of the correcting lens. Calculating the distance from the lens to the new near point of the eye with the correcting lens in front of the eye.

Explanation / Answer

Myopia is most commonly corrected through the use of corrective lenses, such as glasses or contact lenses. It may also be corrected by refractive surgery, though there are cases of associated side effects. The corrective lenses have a negative optical power (i.e. have a net concave effect) which compensates for the excessive positive diopters of the myopic eye. Negative diopters are generally used to describe the severity of the myopia, as this is the value of the lens to correct the eye.

People with long sightedness generally have good vision aside from the refractive error. Refractive errors were traditionally corrected with glasses and contacts.

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