Corneal Biomechanical Alterations in Eyes After Radial Keratotomy Compared With Keratoconus

To investigate the corneal biomechanical characteristics of eyes after radial keratotomy (RK) versus eyes with keratoconus.

In this retrospective case-control study, 15 eyes of 8 post-RK patients, 20 eyes of 20 age-matched patients with keratoconus, and 20 eyes of 20 normal control participants were assessed. Using an air pulse device with dynamic Scheimpflug imaging, corneal biomechanical parameters, including time, velocity, deformation amplitude, and deflection amplitude/length/area, were measured during deformation. Parameters for comprehensive biomechanical screening and ectasia detection were also recorded. In total, 27 corneal biomechanical parameters among the post-RK, keratoconus, and control groups were compared.

There were statistically significant differences in 21 parameters between the post-RK and keratoconus groups and 18 parameters between the post-RK and control groups (P < .05, all). Seventeen of the 21 parameters, including deflection amplitude/length/area, were significantly greater in the post-RK group than in both the keratoconus and control groups (P < .05). Eight parameters in both the post-RK and keratoconus groups were significantly different from those in the control group (P < .05, all). Although less corneal stiffness was observed in the post-RK and keratoconus groups than in the control group, radius-related parameters, the ratio between the deformation amplitude at the apex and at 2 mm, and the difference in corneal thickness from the center to the periphery differed between the post-RK and keratoconus groups.

Dynamic Scheimpflug imaging quantitatively demonstrated that the mechanism of decreased corneal biomechanical characteristics in post-RK eyes differs from that in eyes with keratoconus, which generally causes localized corneal thinning and protrusion around the corneal apex.