Purpose: To compare the posterior keratometry (PK) values obtained with three instruments based on optical coherence tomography (Anterion [Heidelberg Engineering], IOLMaster 700 [Carl Zeiss Meditec AG], and MS-39 [CSO]), and one Scheimpflug camera biometer (Pentacam AXL Wave; Oculus Optikgeräte GmbH). The average keratometry (Kave), total corneal power (TCP), anterior-to-posterior ratio (A/P ratio), and posterior corneal astigmatism (PCA) were also compared.
Methods: Measurements by the four instruments, expressed in diopters (D), were compared using repeated measures analysis of variance, when they were normally distributed, or Friedman's test, when they were not.
Results: One hundred eyes (100 consecutive patients) scheduled to undergo cataract surgery were prospectively enrolled. Statistically significant differences among the Anterion, IOLMaster 700, MS-39, and Pentacam AXL Wave were detected for PK: Anterion: -6.08 ± 0.23 D, IOLMaster 700: -5.77 ± 0.23 D, MS-39: -6.15 ± 0.26 D, and Pentacam AXL Wave: -6.26 ± 0.26 D (P < .0001); for Kave: Anterion: 43.19 ± 1.50 D, IOLMaster 700: 43.35 ± 1.49 D, MS-39: 43.36 ± 1.53 D, and Pentacam AXL Wave: 43.22 ± 1.55 D (P < .0001); for the A/P ratio: Anterion: 1.19 ± 0.02, IOLMaster 700: 1.12 ± 0.02, MS-39: 1.20 ± 0.03, Pentacam AXL Wave: 1.22 ± 0.03 (P < .0001); and for TCP: Anterion: 42.69 ± 1.51 D, IOLMaster 700: 43.36 ± 1.49 D, MS-39: 42.92 ± 1.52 D, and Pentacam AXL Wave: 42.35 ± 1.55 D (P < .0001). PCA revealed significant differences for the KP(45) and KP(0) vectors (P < .0001).
Conclusions: The four instruments showed different PK values. The largest difference was observed with the IOL-Master 700, which provided the flattest PK and the lowest A/P ratio. The measurements cannot be considered interchangeable, and this should be considered when entering PK values into calculators using this parameter for IOL power.