مهندسی پزشکی

information was "filled with false statements, incorrect citations" and "mischaracterization of results".^[17]

A 2016 JAMA study indicates that the prevalence of complications from LASIK are higher than indicated, with the study indicating many patients wind up with glare, halos or other visual symptoms.^[18]

Presbyopia

A type of LASIK, known as presbyLasik, may be used in presbyopia. Results are, however, more variable and some people have a decrease in visual acuity.^[19]

Risks

Higher-order aberrations

Higher-order aberrations are visual problems that require special testing for diagnosis and are not corrected with normal spectacles (eyeglasses). These aberrations include "starbursts", "ghosting", "halos" and others.^[20] Some patients describe these symptoms post-operatively and associate them with the LASIK technique including the formation of the flap and the tissue ablation.^[21]

The advancement of the LASIK technology has reduced the risk of clinically significant visual impairment after surgery.^{[citation needed]} There is a correlation between pupil size and aberrations. This correlation may be the result of irregularity in the corneal tissue between the untouched part of the cornea and the reshaped part. Daytime post-LASIK vision is optimal, since the pupil size is smaller than the LASIK flap. However, at night, the pupil may dilate such that light passes through the edge of the LASIK flap, which gives rise to aberrations. LASIK and PRK may induce spherical aberration if the laser under-corrects as it moves outward from the centre of the treatment zone, especially when major corrections are made.^{[citation needed]}

Others propose that higher-order aberrations are present preoperatively.^[22] They can be measured in micrometers (µm) whereas the smallest laser beam size approved by the FDA is about 1000 times larger, at 0.65 mm. In situ keratomileusis effected at a later age increases the incidence of corneal higher-order wavefront aberrations.^[23][24] These factors demonstrate the importance of careful patient selection for LASIK treatment.