Air-puff induced corneal dynamics in normal, forme fruste and keratoconic eyes measured with OCT-based optical biometry.

• High-speed optical biometry enables assessment of the eye reaction to air-puff stimulus. • The eyes with keratoconus showed higher and longer displacements of the cornea. • No significant differences in extracted parameters between forme fruste keratoconus and normal eyes was revealed. The aim of this study was to characterize corneal dynamic response in normal subjects (NL), patients with forme fruste keratoconus (FFKC) and patients with clinical keratoconus (KC) using air-puff OCT-based optical biometry. This cross-sectional study included 50 normal eyes (NL), 15 forme fruste eyes (FFKC) and 31 eyes with early and moderate keratoconus (KC). Keratometry and pachymetry were performed with MS-39 (CSO, Italy). The dynamic response of the corneal apex to air-puff stimulus was imaged with an optical biometer combined with the air-puff system allowing correction for whole eye retraction. The amplitude and duration of corneal displacement, the maximum velocity of the cornea during loading and recovery and hysteresis loop area were extracted from the data. The differences between NL, FFKC and KC groups were tested and the correlation between extracted biomechanical parameters and age, intraocular pressure (IOP) or corneal geometry was assessed for each group. Maximum corneal displacement was higher in the KC eyes than in the NL eyes (p < 0.001), corneal response was longer and maximum velocity of corneal apex was higher in KC eyes (p < 0.05). No significant difference in extracted parameters was detected between FFKC and NL eyes. The parameters of corneal biomechanical response depended mostly on IOP and corneal thickness in NL eyes. Weaker correlation patterns were found in KC and FFKC eyes. High-speed optical biometry combined with an air-puff stimulation allows for the evaluation of the corneal biomechanics. Keratoconus affects corneal biomechanics but the parameters measured could not effectively distinguish forme fruste keratoconus from normal eyes. [ABSTRACT FROM AUTHOR]