The effect of flap thickness on the visual and refractive outcome of myopic laser in situ keratomileusis

To study the effect of flap thickness on the visual and refractive outcome of myopic laser in situkeratomileusis (LASIK) surgery.

A total of 196 myopic eyes with spherical equivalent (SE) from -2.00 to -5.00 dioptres which underwent LASIK were studied retrospectively. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and manifest refraction were measured up to 6 months postoperatively. Logistic and linear regression analyses were used to examine the correlation of flap thickness to visual and refractive outcomes, postoperative complications and enhancement rate.

UCVA at 1 week and 1 month, but not at 1 day and at 6 months (P>0.05), were negatively correlated to flap thickness (P<0.05). BCVA was unrelated to flap thickness (P>0.05). At 1-month post-LASIK sphere and cylinder were not related to flap thickness (P>0.05), but spherical equivalent was negatively correlated (P<0.05). Significant negative correlations with the sphere and SE were noticed at 6 months for the eyes not requiring enhancements (P<0.05). Flap thickness had no significant relationship to postoperative complications (P>0.05) and no significant predictive value on the rate of enhancement procedures or the efficacy, safety and predictability indices (P>0.05).

In myopic LASIK thinner flaps are associated with faster visual recovery and less myopic SE, but the BCVA and the final UCVA are independent of flap thickness. Postoperative complications are unrelated to flap thickness. Flap thickness does not affect the efficacy, safety and predictability, or the rate of enhancement procedures.