Biomechanics:
Determination of Corneal Elasticity Coefficient Using the ORA Database

Sergei E. Avetisov, MD, PhD; Ivan A. Novikov; Irina A. Bubnova, MD; Alexei A. Antonov, MD and Vladimir I. Siplivyi, MD

PURPOSE

To propose a new approach for the study of corneal biomechanics using the Reichert Ocular Response Analyzer (ORA) database, which is based on changes in velocity retardation in the central cornea at the peak of flattening.

METHODS

The ORA applanation curve was analyzed using a mathematical technique, which allowed calculation of the elasticity coefficient (Ke), which is primarily characteristic of the elastic properties of the cornea. Elasticity coefficient values were obtained in patients with presumably different biomechanical properties of the cornea: “normal” cornea (71 eyes, normal group), keratoconus (34 eyes, keratoconus group), LASIK (36 eyes, LASIK group), and glaucoma with elevated and compensated intraocular pressure (IOP) (38 eyes, glaucoma group).

RESULTS

The mean Ke value in the normal group was 11.05±1.6, and the corneal thickness correlation coefficient r² was 0.48. In the keratoconus group, the mean Ke value was 4.91±1.87 and the corneal thickness correlation coefficient r² was 0.47. In the LASIK group, Ke and r² were 5.99±1.18 and 0.39, respectively. In the glaucoma group, the same eyes that experienced a two-fold reduction in IOP developed a statistically significant reduction in the Ke (1.06 times lower), whereas their corneal hysteresis value increased 1.25 times.

CONCLUSIONS

The elasticity coefficient calculated using the ORA applanation curve can be used in the evaluation of corneal biomechanical properties. [J Refract Surg. 2010;26(7):520-524.]

AUTHORS

From the Research Institute of Eye Diseases of the Russian Academy of Medical Sciences, Moscow, Russia.

Supported by a grant from the Russian Foundation for Basic Research, “Elaboration of methods of mathematical simulation, of experimental and clinical research of biomechanical (strength) properties of cornea” (07-04-01710-a).

The authors have no financial interest in the materials presented herein.

Correspondence: Irina A. Bubnova, MD, 11-a Rossolimo St, Moscow, Russia, 119021. Tel: 79166209921; Fax: 74992480125; E-mail: bubnovai@mail.ru

Received: December 14, 2008; Accepted: September 22, 2009

Posted online: November 2, 2009

doi:10.3928/1081597X-20091030-01