Assessment of corneal biomechanics, tonometry and pachymetry with the Corvis ST in myopia

Xiaorui Wang,Colm Mcalinden,Jie Yan,Hongbing Zhang,Shengjian Mi,Wei Wei,Dan Wang

doi:10.1038/s41598-020-80915-9

Abstract

To evaluate the repeatability of Corvis ST corneal biomechanical, tonometry and pachymetry measurements, and agreement of pachymetry measures with the Pentacam HR and RTVue OCT. Three consecutive measurements of the right eye of 238 myopic subjects were acquired with the Corvis ST, Pentacam HR, and RTVue OCT. Repeatability of Corvis ST was evaluated by within-subject standard deviation [Sw] and repeatability limit [r]. The agreement of central corneal thickness (CCT) measurements were compared among the three instruments using the Bland–Altman limits of agreement. Comparisons were further stratified by CCT (Corneathin ≤ 500 µm; Corneanormal = 500–550 µm; Corneathick > 550 µm). Sw was below 1 mmHg in Corneathin, Corneanormal, and Corneathick groups for IOP and bIOP. Sw for SP-A1 were 4.880, 6.128, 7.719 mmHg/mm respectively. Sw for CBI were 0.228, 0.157, 0.076, and correspondingly Sw for TBI and SSI were 0.094 and 0.056, 0.079 and 0.053, 0.070 and 0.053. The Bland–Altman plots for CCT implied poor agreement with mean differences of 29.49 µm between Corvis and OCT, 9.33 µm between Pentacam and OCT, and 20.16 µm between Corvis and Pentacam. The Corvis ST showed good repeatability with the exception of CBI in the various CCT groups. The CCT measured by Corvis ST was not interchangeable with Pentacam HR and RTVue OCT.

Highlights

Corneal biomechanics play an important role in the diagnosis and characterization of ocular diseases such as corneal ectasia, evaluation for corneal laser refractive surgery candidacy, and post refractive surgery monitoring[1,2,3]
No significant differences in Km or corneal diameter were detected among those three groups
Corneal biomechanical measurement is of significant importance in terms of early detection of corneal ectatic diseases such as keratoconus and post corneal refractive surgery ectasia

Summary

Introduction

Corneal biomechanics play an important role in the diagnosis and characterization of ocular diseases such as corneal ectasia, evaluation for corneal laser refractive surgery candidacy, and post refractive surgery monitoring[1,2,3]. There are some technologies available for the measurement of the ocular biomechanical response, including air-jet infrared light technology (Ocular Response Analyzer, ORA; Reichert, Inc., Depew, NY, USA), air-puff Scheimpflug imaging system (Corvis Scheimplug Tonometer, Corvis ST, Oculus Optikgeräte GmbH, Wetzlar, Germany), air-puff optical coherence tomographer (OCT) (not commercially available) and air-puff biometry (not commercially available)[12,13]. The dynamic Scheimpflug imaging analysis system, Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany), is a device allowing visualization and measurement of the corneal biomechanical response to a standardized air puff pressure concurrently. High-speed imaging allows for analysis of the detailed movement of the cornea during the deformation process, may provide clinically relevant parameters correlated with the biomechanical properties of the cornea. The agreement of CCT measurements using the Corvis ST with the Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany, software version.1.2r43) and the RTVue OCT (Optovue Inc., Fremont, California, USA, software version.2018.0.0.18) centered on the corneal apex were compared

Methods

Results

Conclusion