RK is effective in reducing mild-to-moderate nearsightedness. It does not always completely end nearsightedness. You may still need to wear corrective lenses some of the time for either near or distance vision (or both) after surgery. People who have moderate-to-high nearsightedness before surgery are more likely to still need correction for distance vision after surgery than those who are only mildly nearsighted.
The greatest problems with RK surgery are that the results are harder to predict and they tend to change over time. RK reduces nearsightedness, but it often causes mild farsightedness (overcorrection) or does not completely correct nearsightedness (undercorrection). Results are sometimes several diopters different than predicted. In contrast, eyeglasses and contact lenses are fitted with an accuracy of within 0.5 diopter of the desired correction.
The vision correction after RK also may be unstable. Most people who have RK surgery gradually become more farsighted for at least 8 to 10 years after surgery. This is called the hyperopic shift.
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