Comparison of reliability and repeatability of corneal curvature assessment with six keratometers

• Published in: Clinical and experimental optometry 2016-11, Vol.99 (6), p.583-589
• Main Authors: Hamer, Catriona A, Buckhurst, Hetal, Purslow, Christine, Shum, Gary L, Habib, Nabil E, Buckhurst, Phillip J
• Format: Article
• Language: English
• Subjects: Adult; astigmatism; Astigmatism - diagnosis; Cornea - anatomy & histology; corneal curvature; corneal topography; Corneal Topography - instrumentation; Female; Humans; keratometry; Lenses, Intraocular; Male; Middle Aged; Observer Variation; Reproducibility of Results
• ISSN: 0816-4622; 1444-0938
• DOI: 10.1111/cxo.12329

Keratometric methodology varies between instruments and the differences may have a clinical impact. We investigated the agreement and reproducibility of six keratometers. Keratometry was performed on 100 subjects at two separate sessions with IOLMaster 500, Pentacam, OPD scanner, Medmont E300, Javal-Schiøtz and TMS-5. A second observer assessed 30 subjects to determine inter-observer variability. A single individual was assessed on 10 separate sessions to determine intra-observer variability. Data were analysed using coefficient of variation (CV) and intra-class correlation coefficient (ICCC) for intra-observer variation. Inter-observer concordance was evaluated by the ICCC. Bland-Altman plots, Pearson's correlation coefficient and repeated measures analysis of variance were used to assess agreement of data produced by the instruments. OPD scanner and Javal-Schiøtz mean spherical equivalent (MSE) results were systematically different (p < 0.001) from other instruments (flatter and steeper, respectively). J 0 /J 45 were similar for all instruments (p < 0.05). Bland-Altman comparison plots indicated that Pentacam and IOLMaster demonstrated greatest level of agreement (ICC results MSE = 0.992, J 0 = 0.934 and J 45 = 0.890). Agreement (ICC) between observers for MSE ranged from 0.955 to 0.995 for all instruments; lower levels of agreement were found for J 0 /J 45 (0.289 to 0.901). IOLMaster showed greatest correlation and Medmont the lowest. All instruments showed high intra-observer repeatability of MSE (CV 0.1 to 0.3 per cent). The J 0 /J 45 readings showed greater variability (CV range 8.8 to 57.6 per cent). When considering MSE alone IOLMaster, Pentacam, OPD scan and Medmont may be considered interchangeable; however, assessment of astigmatism shows greater variability between instruments, sessions and observers.