Comparative study of stromal bed quality by using mechanical, IntraLase femtosecond laser 15-and 30-kHz microkeratomes

Purpose: To evaluate corneal stromal bed quality of lamellar keratectomy in laser in situ keratomileusis (LASIK) procedures by using mechanical and femtosecond laser microkeratomes. Methods: LASIK corneal flaps were created in 9 fresh human globes not suitable for transplantation. We grouped the samples into 3 different groups of 3 globes each. Group 1 was the control group, in which the flaps were created using a Hansatome microkeratome with a 160-mu m head. Groups 2 and 3 consisted of flaps created at the 110-mu m flap thickness setting using the IntraLase 15- and 30-kHz femtosecond laser, respectively. All the flaps were removed, and the corneal stromal beds were prepared for scanning electron microscopy (SEM). Qualitative surface roughness (QISR) of the SEM images was graded using a roughness grading scale from I to 5 by 3 masked observers. Quantitative surface roughness (QnSR) of the SEM images was also assessed using software designed for roughness analysis. Mann-Whitney nonparametric statistical analysis was performed to compare groups. Results: There was no statistically significant difference in QISR and QnSR scores between group 2 and group 1 (brand-new blade only). Group 3 30-kHz IntraLase samples showed a smoother stromal bed compared with group 1 and 2 samples. This was a statistically significant difference for Q1SR (Q1SR = 1.1 +/- 0.17, P < 0.001) and showed borderline significance for QnSR (QnSR = 24.4 +/- 0.96, P = 0.05). Conclusions: The IntraLase 15-kHz femtosecond laser 110-mu m flaps and the Hansatome 160-mu m head using a new blade both produced smooth, good-quality, compact stromal beds as assessed qualitatively by masked observers and quantitatively by image analysis software. The 30-kHz femotsecond laser permits a tighter spot/line separation and lower energy per pulse, which creates smoother corneal stromal beds.