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Impact of quality indicators on variability of keratometry measurements using a SS-OCT-based optical biometer
Nathan T Cannon1, David L Cooke, Jascha A Wendelstein
1From the Department of Ophthalmology, Penn State College of Medicine, Hershey, Pennsylvania (Cannon, Lehman, Pantanelli); Great Lakes Eye Care, St. Joseph, Michigan (Cooke); Institute of Experimental Ophthalmology, Saarland University, Homburg, Germany (Wendelstein); Institut für Refraktive und Ophthalmo-Chirurgie (IROC), Zurich, Switzerland (Wendelstein); Department for Ophthalmology and Optometry, Kepler University Hospital GmbH, Linz, Austria (Wendelstein); Johannes Kepler University Linz, Medical Faculty, Linz, Austria (Wendelstein).
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 (∆Kmean) and total keratometry (∆TKmean) as well as standard astigmatism (∆Kastig) and total astigmatism (∆TKastig) vectors were calculated.
Results:
Analysis was performed on 3222 eyes of 1890 patients. Measurement "success" was associated with a smaller ΔKmean (0.09 ± 0.14 diopters [D]) and ΔTKmean (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 ∆Kastig (0.26 ± 0.28 D) and ∆TKastig (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 ∆Kastig >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.
