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There has been considerable attention paid to the optical consequences of corneal refractive surgery, particularly those occurring during the night time when the pupil widens and larger areas of the sculpted cornea are included within the visual pathway. It seems a forgone conclusion that pupils larger than the functional optical zone (the area of the corneal surface after laser sculpting that provides quality vision1) created by the surgery should cause problems for the patient and, in truth, this has occurred with night vision complaints that include starburst effects and haloes. Therefore, it has been the strategy over the course of technique development for laser algorithms to sculpt ever larger corneal areas encompassing the full correction zone (the zone of intended refractive correction) and to incorporate cleverly designed surrounding transition zones to blend in curvature changes in a smoother fashion.1 Taken together, these changes have reduced or eliminated many of the night vision complaints that were associated with pupil diameter, at least in some recent reports.2,3
In this issue, Villa and associates (see page 1031),4 have re-examined this problem in successful LASIK patients by using a commercial device to measure a night vision disturbance metric, the “halo disturbance index.”. They also measured the dark-adapted pupil size and the calculated optical aberrations arising from the corneal surface. In this careful study, the authors demonstrate that the halo disturbance index correlates strongly with specific aberrations: notably, spherical …
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