Intraoperative Noncontact Online Pachymetry for Measurement of Corneal Flap Thickness in LASIK Surgery
Narrative Responses:
Purpose
To evaluate the efficacy, predictability and accuracy of Non.Contact Online Pachymetry in LASIK surgery for measurement of flap and residual stromal bed thickness
Methods
In a prospective, nonrandomized, comparative clinical study of 237 eyes of 139 patients central corneal pachymetry was optically measured preoperatively (Pentacam) and intraoperatively using Online Non-Contact Pachymetry (Wavelight Ex-500 Excimer Laser). Corneal flap thickness was calculated by subtracting the corneal stromal thickness from the total corneal thickness. A single-use microkeratome head (Moria One) was used for creating a 90 or 130 µm corneal flap. The same surgeon performed all procedures using a new blade for each patient and the same surgical technique.
Results
The mean flap thickness using 130 µm microkeratome head was 136,5 µm ± 16,8 (SD) and with the 90 µm head was 98,7 µm ± 13,6 (SD) . The mean intraoperative central corneal thickness values were 13.7 μm lower than the preoperative optically determined values (Pentacam). There was a significant correlation (P<.001) between the postoperative flap (r = 0.79) and the estimated microkeratome head cut.
Conclusion
In planning the surgery, many surgeons make assumptions about flap thickness based on the manufacturer's labeling of the microkeratome. Based on previous reports, there is a degree of variation in flap thickness; an assumption about flap thickness may be unwise. Intraoperative no contact pachymetry is a safe and predictable tool for flap and residual stromal bed measurement.