Prospective comparison of single-zone and multizone laser in situ keratomileusis for the correction of low myopia.
OBJECTIVE
This study aimed to determine whether there is a true difference in predictability between single-zone and multizone laser in situ keratomileusis (LASIK) for the correction of low myopia or whether any difference in predictability is because of a need for separate clinical nomograms for the two treatments.


METHODS
A prospective, randomized, clinical trial.


METHODS
Fourteen surgeons and 190 eyes of 95 patients with myopia who desired surgical correction of myopia ranging from -2.00 to -7.00 diopters (D) participated.


METHODS
Fellow eyes of patients with myopia undergoing bilateral simultaneous LASIK were randomized to single-zone and multizone ablation. Astigmatism was not corrected at the time of LASIK.


METHODS
Predictability, postoperative videokeratography, and contrast sensitivity were assessed at 3 months after surgery.


RESULTS
At 3 months, r2 values relating laser setting to change in spherical equivalent refraction were 0.78 for single-zone and 0.76 for multizone ablation; mean outcome with respect to intended was -0.84 D (0.65 standard deviation [SD]) for single-zone and -0.62 D (0.78 SD) for multizone eyes (P = 0.035). There was no relationship between single-zone and multizone ablation and the likelihood of asymmetric postoperative videokeratography (P = 0.83). The only difference in contrast sensitivity was a significantly greater decrease in log contrast for multizone eyes at 12 cyc/deg under undilated conditions.


CONCLUSIONS
There is no true difference in predictability between single-zone and multizone LASIK for the correction of low myopia. Separate clinical nomograms for single-zone and multizone LASIK should eliminate the difference in predictability that was observed in this clinical trial.
Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia, USA.
J D
JD
Carr
R D
RD
Stulting
Y
Y
Sano
K P
KP
Thompson
W
W
Wiley
G O
GO
Waring
D000293:Adolescent; D000328:Adult; D000368:Aged; D015350:Contrast Sensitivity; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D019781:Corneal Topography; D016039:Corneal Transplantation / Q000379:methods*; D005260:Female; D006801:Humans; D053685:Laser Therapy; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016896:Treatment Outcome