Intraocular pressure measurements and corneal biomechanical properties using a dynamic Scheimpflug analyzer, after...

To evaluate the biomechanical properties of the cornea and their impact on intraocular pressure (IOP) measurement after lamellar keratoplasty, compared to healthy eyes, using a non-contact tonometer with a Scheimpflug camera.

This study, from 2014 to 2015, included 22 primary DSAEK, 5 DALK, 6 DSAEK after PK, and 50 control eyes. Using a non-contact tonometer with a high-speed Scheimpflug camera (CORVIS ST, Oculus Optikgeräte GmbH, Wetzlar, Germany), several biomechanical parameters were recorded, including radius at highest concavity (R_hc) and defomation amplitude (DA). Central corneal thickness (CCT) and uncorrected IOP, were also recorded. For the control eyes only, a corrected IOP was calculated, based on age, central corneal thickness, and biomechanical parameters.

R_hc was significantly lower after DALK (R_hc=5.54±0.71, P=0.007) and DSAEK (R_hc=6.26±0.77, P=0.042) compared to control eyes (R_hc=6.82±0.76). DA was higher after DALK and DSAEK, but not significantly (respectively 1.24±0.09 P=0.41 and 1.22±0.15, P=0.923) compared to normal eyes (1.18±0.15). Uncorrected IOP was not significantly different between post-keratoplasty and control eyes. In control eyes, the corrected IOP (15.23±1.88) was lower than the uncorrected IOP (16.10±2.34); a statistically significant positive correlation between R_hc and CCT (R²=0.6020, P<0001), and a significant negative correlation between DA and CCT (R²=-0.641, P<0.0001) were found.

Our study showed that, after lamellar keratoplasty, corneal biomechanics are altered. Corneas with higher ocular rigidity will show a lower DA and a higher R_hc.