Comparison of keratometry measurements using the Pentacam HR, the Orbscan IIz, and the TMS-4 topographer.
OBJECTIVE
To compare and evaluate the agreement between keratometry readings using three devices: the Pentacam HR, the Orbscan IIz, and the TMS-4 topographer.


METHODS
In this prospective comparative study, 115 eyes from 115 healthy refractive surgery candidates were sequentially examined using three devices. Fourier analysis was used to evaluate corneal astigmatism in these subjects. The outcome measures comprised steep and flat keratometry readings, corneal astigmatism, the mean keratometry reading, and the J0 and J45 components. Repeated-measures analysis of variance (RM-anova) and Bland-Altman plots with 95% limits of agreement were used to evaluate the difference between measurements.


RESULTS
The mean keratometry readings were 43.89 ± 1.51, 43.52 ± 1.48, and 43.79 ± 1.50 D using the TMS-4 topographer, the Orbscan IIz, and the Pentacam HR, respectively (p < 0.001; RM-anova). The mean keratometric astigmatism was 1.27 ± 0.87, 1.20 ± 0.86, and 1.21 ± 0.82 D using the TMS-4 topographer, the Orbscan IIz, and the Pentacam HR, respectively (p = 0.007; RM-anova). The J0 measurements were higher using the TMS-4 topographer compared with the Orbscan IIz (p = 0.021; Bonferroni test). The mean, steep, and flat keratometry data were in better agreement using the TMS-4 topographer and the Pentacam HR. In general, the Orbscan IIz device measured lower values than either the TMS-4 topographer or the Pentacam HR. However, the corneal astigmatism measurements and the J0 component showed the best agreement using the TMS-4 topographer and the Orbscan IIz.


CONCLUSIONS
The TMS-4 topographer and the Pentacam HR produced similar readings and can be used interchangeably to measure simulated keratometry values in young, healthy eyes. To measure corneal astigmatism, the TMS-4 topographer and the Orbscan IIz produced values that were similar and could be used interchangeably.
International Branch, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Zahra
Z
Tajbakhsh
Ramin
R
Salouti
Mohammad H
MH
Nowroozzadeh
Mohammad
M
Aghazadeh-Amiri
Seyedmehdi
S
Tabatabaee
Mohammad
M
Zamani
D000328:Adult; D000704:Analysis of Variance; D001251:Astigmatism / Q000473:pathology*; D003316:Corneal Diseases / Q000473:pathology*; D019781:Corneal Topography / Q000295:instrumentation*; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D011446:Prospective Studies; D055815:Young Adult