Evaluation of Intraocular Pressure and Other Biomechanical Parameters to Distinguish between Subclinical Keratoconus and Healthy Corneas.

Cristina Peris-Martínez,Susana Ortí-Navarro,María Dolores Pinazo-Durán,María Carmen García-Domene,María Amparo Díez-Ajenjo,María Ángeles Del Buey-Sayas,María José Luque-Cobija

doi:10.3390/jcm10091905

Abstract

(1) Purpose: To assess the main corneal response differences between normal and subclinical keratoconus (SCKC) with a Corvis® ST device. (2) Material and Methods: We selected 183 eyes of normal patients, of a mean age of 33 ± 9 years and 16 eyes of patients with SCKC of a similar mean age. We measured best corrected visual acuity (BCVA) and corneal topography with a Pentacam HD device to select the SCKC group. Biomechanical measurements were performed using the Corvis® ST device. We carried out a non-parametric analysis of the data with SPSS software (Wilcoxon signed rank-test). (3) Results: We found statistically significant differences between the control and SCKC groups in some corneal biomechanical parameters: first and second applanation time (p = 0.05 and p = 0.02), maximum deformation amplitude (p = 0.016), highest concavity radius (p = 0.007), and second applanation length and corneal velocity ((p = 0.039 and p = 0.016). (4) Conclusions: Our results show that the use of normalised biomechanical parameters provided by noncontact tonometry, combined with a discriminant function theory, is a useful tool for detecting subclinical keratoconus.

Highlights

Knowledge of corneal biomechanics is essential to understand corneal behaviour in certain diseases, surgical procedures, intraocular pressure (IOP) measurements, and in the early detection and treatment of subclinical keratoconus (SCKC).Keratoconus is a bilateral, inflammatory, asymmetric and progressive corneal ectasia disorder
Some studies found a good correlation between keratoconus and low corneal hysteresis (CH) and corneal resistance factor (CRF) in high grade keratoconus [7,8,9,10,11]
Diagnosis of SCKC was made when eyes had no clinical signs of keratoconus (Vogt’s striae, Fleischer rings or corneal scarring), their topography was normal with no asymmetric bowtie, and no focal or inferior steepening pattern

Summary

Introduction

Knowledge of corneal biomechanics is essential to understand corneal behaviour in certain diseases, surgical procedures, intraocular pressure (IOP) measurements, and in the early detection and treatment of subclinical keratoconus (SCKC). Keratoconus is a bilateral, inflammatory, asymmetric and progressive corneal ectasia disorder. The collagen network is mostly unorganised, with decreased fibrillar interweaving [3,4,5]. These changes reduce corneal stiffness [2,5]. The most commonly used device for analysing corneal biomechanical parameters is the Ocular Response Analyzer (ORA® , Reichert Ophthalmic Instruments, Inc., Buffalo, NY, USA) [4,5,6,7,8]. Some studies found a good correlation between keratoconus and low corneal hysteresis (CH) and corneal resistance factor (CRF) in high grade keratoconus [7,8,9,10,11]

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Methods

Conclusion