Impact of quality indicators on variability of keratometry measurements using a SS-OCT-based optical biometer

Purpose: To characterize the variability of keratometry measurements on the IOLMaster 700 and relate it to device image quality indicators (QIs). Setting: 2 academic centers and 1 private practice. Design: Multicenter, retrospective consecutive case series. Methods: Measurements from 3 sites, obtained between December 2015 and July 2023, were included. Surgery-naïve phakic eyes with same-day sequential measurements on the same eye were identified. Repeat measurement pairs were grouped by IOLMaster QIs (success vs warning), and changes in mean standard keratometry (ΔKmean) and total keratometry (ΔTKmean) as well as standard astigmatism (ΔKastig) and total astigmatism (ΔTKastig) vectors were calculated. Results: Analysis was performed on 3222 eyes of 1890 patients. Measurement “success” was associated with a smaller DKmean (0.09 ± 0.14 diopters [D]) and DTKmean (0.11 ± 0.16 D) when compared with pairs in which both measurements had a “warning” (0.25 ± 0.32 D and 0.14 ± 0.17 D, respectively; P <.0001). A similarly smaller ΔKastig (0.26 ± 0.28 D) and ΔTKastig (0.28 ± 0.30 D) were observed with measurement “success” vs “warning” (0.77 ± 0.79 D and 0.42 ± 0.41 D, respectively; P <.0001). Even when both measurements were successful, the proportion of measurement pairs that had a ΔKastig >0.50 D increased from 14% to 24% to 32% when Kmean SD was ≥0.01, 0.05, and 0.10 D, respectively. Conclusions: When measurement quality is poor, TK varies less than standard K measurements. Clinicians may use the SD of Kmean/ TKmean to estimate the repeatability of measurements and balance this against their tolerance for performing repeat measurements.