Tomographic Analysis of Anterior and Posterior and Total Corneal Refractive Power Changes After Femtosecond Laser–Assisted Keratotomy

Abstract

To analyze the effect of penetrating femtosecond laser-assisted keratotomy (pFLAK) during laser lens surgery on anterior and posterior corneal astigmatism and total corneal refractive power (TCRP) astigmatism (CAant, CApost, CATCRP) measured with Scheimpflug tomography. Prospective, interventional case series. This institutional study included 27 eyes of 23 patients (aged 65 ± 8 years) with low-to-moderate CATCRP determined with Scheimpflug tomography (Pentacam HR; Oculus, Wetzlar, Germany) after penetrating femtosecond laser-assisted keratotomy (pFLAK) and laser lens surgery. The CAant, CApost, and CATCRP were determined before and 1 and 3months after surgery. Vector analysis according to the Alpins method was used to calculate surgically induced astigmatism (SIA). The mean preoperative CAant (0.97 ± 0.30 diopter [D]) was significantly reduced to 0.63 ± 0.34 D (P < .001). SIAant was 0.71 ± 0.37 D. The CApost showed no significant change, from preoperative 0.26 ± 0.12 D to 0.26 ± 0.10 D postoperatively (P= .625). In line with this finding, SIApost was low (0.12 ± 0.07 D). The CATCRP showed similar results as CAant. pFLAKs planned according to Scheimpflug-based CATCRP result in a significant reduction of the CAant and CATCRP, but do not affect the posterior corneal curvature significantly, as measured by Scheimpflug tomography. Further research is required to develop a new valid nomogram for laser-assisted lens surgery.