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D.B. Miranda1A, S.Smith1B, R.R. Krueger1A.
AOphthalmology
BOphthalmology
1COLE EYE INSTITUTE, CLEVELAND CLINIC FOUNDATION, Cleveland, OH.
Purpose: To compare flap thickness and the reproducibility of four types of microkeratomes during laser in situ keratomileusis (LASIK).
Methods: A series of 490 consecutive eyes underwent laser in situ keratomileusis (LASIK) by one surgeon and were evaluated for the depth of flaps measured via subtractive pachymetry. All flaps were created using either the B&L Hansatome180 head, the Moria CB 160 head, the Moria M2 110 head or the Alcon SKBM 160 head. The mean preoperative pachymetry was 547.6 34.31 m the mean steep keratometric reading was 44.32 1.53 D with a mean flat keratometric reading of 43.42 1.50D.
Results: The flap thickness measurement differed according to the microkeratome used: it was 131 27.84 m in 41 eyes (8.36%) with the B&L Hansatome 180 head; 157 40.0 m in 65 eyes (13.26 %) with the Moria CB 160 head; 134 23.45 m in 257 eyes (52.44%) with Moria M2 110 head; and 162 21.17 m in 127 eyes (25.91%) with the Alcon SKBM 160 head. Considering the average error from the mean flap thickness for each microkeratome, the flap thickness with the SKBM and Moria M2 was statistically significantly more reproducible than with Moria CB (p<0.0005). Based on this sample size, there is no correlation between flap thickness reproducibility and the age, corneal thickness, and corneal keratometric values. However, considering all the microkeratomes, female gender had statistically significantly more variability than male gender(p<0.02). Although thicker corneas were associated with thicker flaps, this was due to indirect measurement error of the subtractive technique.
Conclusion: Based on these results, the greatest predictability of flap thickness was seen with the SKBM and Moria M2, which both use a second motor for advancement. Flap predictability is important in minimizing flap striae and other complications associated with thin flaps, and ectasia associated with thick flaps that compromise the threshold of residual stroma. The greatest variability noted with the Moria CB was probably due to the manual translation feature and places further importance on the second motor and automation.
Commercial Relationship: D.B. Miranda, None; S. Smith, None; R.R. Krueger, ALCON R.
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