Purpose:

To study the changes in posterior corneal astigmatism in myopic femto-flap LASIK & SMILE over 3 months postoperative period.

Methods:

Prospective longitudinal study of posterior corneal imaging [average keratometry (avKM) & posterior corneal astigmatism (PCA)] with Cassini Raytracing & Pentacam Scheimpflug imaging in 38 LASIK eyes & 36 SMILE eyes at preoperative, postoperative month (M) 1 & 3. Details on uncorrected & best corrected visual acuity (UCVA, BCVA), mean refractive spherical equivalent (MRSE), ablation depth (AD), flap thickness (FT), percentage tissue altered (PTA), was noted. Vector analysis of posterior corneal astigmatism was done.

Results:

Mean avKM changed from -6.53D to -6.28D & -6.46D in LASIK; from -6.42D to -6.39D & -6.42D in SMILE at M1&3 respectively in Raytracing imaging. In Scheimpflug imaging avKM changed from -6.23D to -6.26D & -6.21D in LASIK; from -6.29D to - 6.26D & -6.26D in SMILE at M1 & 3 respectively. Vector analysis showed a change in J0 from -0.13 in LASIK to -0.03 and -0.13 at M 1(p=0.04) & M3(p=0.02) ; from -0.1 in SMILE to -0.1and -0.09 at M1(p=1) & M3(p=1). J45 showed a change from 0.01 in LASIK to 0.02 and 0.00 at M1(p=1) & M3(p=0.67); from 0.00 in SMILE to 0.02 and -0.01 at M1(p=1) & M3(p=1) by Ray tracing imaging. Vector analysis did not show significant changes in J0 and J45 by Scheimpflug imaging.

Conclusions:

Raytracing imaging of posterior cornea over 3month postoperative period detected significant PCA changes in myopic femto-flap LASIK but not in SMILE. Scheimpflug’s imaging did not detect any statistically significant PCA changes in both LASIK and SMILE.