Comparison of keratometry using SS-OCT and dual Scheimpflug-Placido imaging in postmyopic corneal refractive surgery eyes

PURPOSE: To compare simulated (SimK) and total (True-K) keratometry and corneal astigmatism values between the IOLMaster 700 (IOLM) and Galilei G4 (G4) devices in postmyopic laser refractive surgery eyes. SETTING: Methodist Eye Associates, Blanton Eye Institute, Houston Methodist Hospital, Houston, Texas. DESIGN: Retrospective cohort study. METHODS: A chart review was conducted on patients with prior myopic laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK), undergoing phacoemulsification at a single institution from May 2019 through January 2022, who underwent imaging with both the IOLM and G4. Exclusion criteria were prior radial keratotomy, keratoectatic diseases, and inability to obtain a reliable image. Mean, flat, and steep SimK and True-K (TK from the IOLM and TCP IOL from the G4) values and astigmatism magnitude were compared. RESULTS: 50 eyes of 50 patients were included. The mean difference in SimK and True-K between devices (IOLM - G4) was -0.04 (95% CI -0.13 to 0.06; P > .05) diopters (D) and 1.14 (95% CI 1.02 to 1.25; P < .05) D, respectively. The IOLM measured steeper True-K values than the G4. There were no statistically significant differences between devices for all other SimK values, whereas for True-K there were significant differences in flat K and steep K ( P < .05), but not astigmatism magnitude. CONCLUSIONS: Despite an overall good correlation in postmyopic laser refractive surgery eyes in keratometry and astigmatism measurements, there is a significant difference in True-K, with the IOLM measuring steeper values by about 1.0 D compared with the G4, similar to prior studies on nonrefractive surgery eyes.