Purchase this article with an account.
J.I. Velarde, D. Ortiz, J. Llorca, F. Gonzalez, J.N. Fernandez del Cotero; Searching for Unintended Central Corneal Flattening Caused by Biomechanical Alteration in LASIK Surgery . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2554.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose:To evaluate the amount of unintended central corneal flattening induced by LASIK surgery and to study its relationship with the flap diameter and the ablation depth. Methods:The retrospective study included 136 eyes of 76 patients (37 men, 39 women), aged 32,7 ± 8.1 years (range 19 - 59) with myopia or myopic astigmatism who had undergone a LASIK surgery using a NIDEK EC-5000 FLEXSCAN excimer laser and a Moria 2 microkeratome. The procedures presented a flap diameter between 8.75 to 9.75 mm, an optical zone from 5.7 to 6.3 mm, and a transition zone from 7.5 to 8 mm. Unintended corneal flattening was defined by the difference between the average central topographic corneal power measured one month after the surgery (Orbscan II ) and postoperative corneal curvature predicted by the laser software (ver 1.20). A linear regression with flattening as a dependent variable and flap diameter and ablation depth as independent variables was done. Results: The mean value and standard deviation of the corneal flattening was –0.64 ± 0.64 D (range -3.5 to +1.79). In the global analysis, the obtained regression coefficient for flattening and flap were 0.120 (p = 0.523), CI (-0.250, 0.489), and for flattening and ablation 0.0003 (p = 0.879), CI (-0.0038, 0.0044). In the group of flap diameter < 9 mm, the regression coefficient for flattening and ablation was –0.009 (p = 0.08), CI (-0.019, 0.0011), but for the other ranges the result wasn’t statistically significant. Conclusions: The different unintended central corneal flattening theoretically induced by biomechanical changes in a LASIK surgery serie has been determined. A statistically significant relationship between flattening and flap diameter and ablation depth was not found. Only for flap diameter minor than 9 mm, the ablation depth had a significant influence in the flattening.
This PDF is available to Subscribers Only