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T. J. Doherty, R. Stulting; Influence of Flap Thickness on Visual Outcomes and Visual Recovery After Lasik Surgery. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5348.
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To analyze the influence of flap thickness on the overall visual acuity and achievement of uncorrected visual acuity levels equal to or better than preoperative best-corrected visual acuity (BCVA) at 24 hour, 2 week and 3 month follow-up visits after laser in situ keratomileusis surgery (LASIK).
This comparative retrospective study comprised of 143 eyes from 93 patients with myopic spherical equivalents ranging from -0.5 to -9.5 who had undergone Lasik surgery. All patients had the surgery performed with the Allegretto Wavelight laser by the same surgeon (RDS). All flaps for the procedure were cut with the Amadeus I Microkeratome system using either AMO or Medlogics plano microkeratome blades. Charts were retrospectively reviewed and patients were divided into 2 groups depending on flap thickness (group 1, flap thickness < 120 microns; group 2, flap thickness ≥120 microns). Flap thickness ranged from 69 to 187 microns. For each group pre-operative best spectacle corrected visual acuity (BSCVA) was recorded, as well as uncorrected visual acuity (UCVA)at the 24 hour, 2 week and 3 month post-operative visits. Correlation between flap thickness and visual acuity were analyzed. The percent of patients in each group that achieved a UCVA greater than or equal to the pre-operative BSCVA was also compared at each time interval.
At no time interval did the difference in the postoperative UCVA between the two groups reach statistical significance (24 hour, P=0.72; 2 week, P=0.95; 3 month, P=0.28). The percentage of each group achieving visual acuity equal to or better than pre-operative BSCVA was 59% and 52% at 24 hours, 71% and 59% at 2 weeks, and 63% and 70% at 3 months for group 1 and group 2 respectively. These differences also failed to reach statistical significance (24 hour, P=0.79; 2week, P=0.23; 3month, P=0.24)
Flap thickness greater than or less than 120 microns bears no effect on overall visual acuity or rate of visual recovery to preoperative visual levels after Lasik surgery. Although other studies have reported significant differences in visual outcomes depending on flap thickness, our evidence does not support these results, at least at this flap thickness.
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