Reproducibility of Flap Thickness in Sub-Bowman Keratomileusis Using a Mechanical Microkeratome
To examine the predictability of flap thickness using a mechanical microkeratome (One Use-Plus) and identify factors related to variations in flap thickness insub-Bowman keratomileusis (SBK).
Patients with a stable refraction for 1 year, corrected distance visual acuity (CDVA) of at least 20/20 in each eye, and minimum central corneal thickness of 480 µm in each eye had microkeratome-assisted SBK. Parameters included manifest refraction, uncorrected distance visual acuity (UDVA), CDVA, pachymetry, and higher-order aberrations (HOAs).
Seventy eyes were enrolled. The mean flap thickness was 88.74 µm ± 15.40 (SD) and the mean change in HOAs, 0.11 ± 0.30 µm2. There was no correlation between flap thickness and age preoperative manifest refraction spherical equivalent (MRSE)preoperative cylinder, postoperative CDVA ,or postoperative change in HOAs. A strong positive correlation with preoperative pachymetry (r = 0.41) and a weak negative correlation with preoperative sphere (r = −0.21) were observed. There was no or a moderate negative correlation of pachymetry with age, preoperative sphere, cylinder, or MRSE.
The microkeratome was reliable with reasonable predictability for SBK flap creation. Extra caution in handling the flaps to avoid flap striae or tears is advised. Flap thickness correlated positively with preoperative pachymetry; however, the variation in flap thickness did not affect visual outcomes.