Corneal biomechanical changes in patients with thin cornea

Abstract

Objectives The aim of this study was to evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in healthy eyes with a central corneal thickness of 470–500 μm with matched keratoconus (KC) and keratoconus suspect (KCS) cases. Background The ocular response analyzer is a device developed in recent years that reveals the biomechanical properties of the cornea. It reflects certain biomechanical properties of the cornea, such as CH and CRF. Patients and methods A total of 66 eyes in three groups were included prospectively based on clinical examination and topography: the normal (NL), KC, and KCS groups. CH and CRF were measured using the ocular response analyzer. CH and CRF were compared between the three groups using the analysis of variances test. Results The three groups consisted of 32 NL, 15 KC, and 19 KCS eyes. The mean CH measured was 8.55 ± 1.77, 9.03 ± 1.119, and 8.06 ± 0.85 mmHg in NL, KCS, and KC eyes, respectively. The mean CRF was 8.39 ± 1.47, 8.27 ± 1.09, and 7.24 ± 1.27 mmHg in NL, KCS, and KC eyes, respectively. On controlling the central corneal thickness (470–500 μm) and sex, only mean CRF was significantly different between the NL and KC groups (P 0.05). Conclusion Only CRF can be helpful in differentiating KC from NL eyes; however, it is not valuable for detecting KCS, which is the main concern for refractive surgery. CH is not beneficial in differentiating between the study groups. Future studies focusing on more accurate tests for identifying KCS using a consistent grading scale for defining KC and KCS are still warranted.