Reproducibility, and repeatability of corneal topography measured by Revo NX, Galilei G6 and Casia 2 in normal eyes

Abstract

PurposeTo test the repeatability and reproducibility of the topography module in posterior segment spectral domain optical coherence tomography with Revo NX (new device) and to compare keratometry values obtained by a Scheimpflug tomography (Galilei G6) and a swept source OCT (Casia 2). MethodsIn this prospective study, healthy subjects with nonoperated eyes had their central corneal thickness (CCT), anterior and posterior K1/K2 corneal power measured with the new device. Two operators made 6 measurements on the new device to check intraobserver repeatability and reproducibility, and measurement on Casia 2 and Galilei G6. Bland-Altman plots were used to assess the agreement between the devices for each analyzed variable. Results94 eyes (94 patients) were studied. All devices produced significantly different mean CCT, the highest for Galilei 569.13±37.58 μm followed by Casia 545.00 ±36.15 μm and Revo 537.39±35.92 μm. The mean anterior K1 was 43.21 ± 1.37 for Casia 2 43.21 ± 1.55 for Revo NX and 43.19 ± 1.39 for Galilei G6, and the differences were insignificant p = 0.617. The posterior K1 for Revo NX was -5.77 ± 0.25 whereas for Casia 2 it was -5.98±0.22 and for Galilei G6-6.09±0.28 D p< 0.0001. The Revo NX showed intraclass correlation coefficient ranging from 0.975 for the posterior K2 surface, and 0.994 for anterior K1 and 0.998 for CCT. ConclusionsRevo NX is independent of the user and offers a high level of repeatability for the anterior and posterior cornea. The wide range of differences between the devices suggests they should not be used interchangeably.

Comparison of ocular biometric measurements in patients with cataract using three swept-source optical coherence tomography devices

“…Considering that the 0.5 D is the currently used IOL power step, the total keratometry values derived from each device should not be interchanged when calculating IOLs. The discrepancy of the three devices in total keratometry could be caused by the different algorism for calculating total keratometry in each device [5,8,19]. IOLMaster 700 obtains anterior keratometry with 18 reflected spots in hexagonal patterns at three zones (1.5 mm, 2.5 mm, and 3.5 mm) and posterior keratometry with SS-OCT tomography [16,20].…”

<p>Repeatability of OCT-Based versus Scheimpflug- and Reflection-Based Keratometry in Patients with Hyperosmolar and Normal Tear Film</p>

“…41,42 Wylegala et al reported a CR of anterior and posterior corneal power (in two meridians) with a spectral domain OCT (Revo NX) to be 0.33-0.46 and 0.10-0.11, respectively. 24 One study reported a CR with the Pentacam for K1/K2 and astigmatism to be 0.07 and 0.39-0.44, respectively, for both SimK and TCP, and 0.11 and 0.12, respectively, for PCP. 43 Another study found that repeatability was worse for anterior elevation but better for posterior elevation with the Casia compared to the Pentacam.…”

“…While combined systems offer lower price and higher resolution due to shorter wavelength of light, the lack of collimated light at the cornea makes the measurements distance-dependent. 24 Dedicated AS systems offers better tissue penetration and imaging depth due to of higher wavelength of light, and also larger measurement diameter. 24,25 The aim of this study was to compare the repeatability of keratometry between different instruments in patients with a hyperosmolar tear film and a control group of patients with a normal tear film.…”

“…24 Dedicated AS systems offers better tissue penetration and imaging depth due to of higher wavelength of light, and also larger measurement diameter. 24,25 The aim of this study was to compare the repeatability of keratometry between different instruments in patients with a hyperosmolar tear film and a control group of patients with a normal tear film. Our hypothesis was that keratometers that do not rely on reflections from the precorneal tear film would be less dependent on tear-film quality than traditional reflection-based keratometers.…”

Refractive Precision of Ray Tracing IOL Calculations Based on OCT Data versus Traditional IOL Calculation Formulas Based on Reflectometry in Patients with a History of Laser Vision Correction for Myopia

“…However, some studies have shown lower repeatability of OCT-based keratometry compared to reflectometry or Scheimpflug-based keratometry. 26–29 …”