Repeatability of a novel corneal indentation device for corneal biomechanical measurement

PurposeThe aim of the study was to evaluate the repeatability of a new device for measuring corneal biomechanics. MethodsTwenty-nine normal subjects aged 20-28years (23.41.7years) underwent measurements of corneal stiffness and tangent elastic modulus using a novel corneal indentation device. Corneal topography, axial biometry and Goldmann applanation tonometry were also performed during the visit. Subjects returned after about 1week, at approximately the same time, and with the corneal biomechanics, corneal topography and Goldmann applanation tonometry measured again. Both the intrasession and intersession repeatability was assessed. ResultsBoth the corneal stiffness and tangent elastic modulus demonstrated good intrasession repeatability (corneal stiffness: coefficient of variation=7.32%, intraclass correlation coefficient=0.75; tangent elastic modulus: coefficient of variation=7.34%, intraclass correlation coefficient=0.84). The mean modulus after normalised to normal intraocular pressure of 15.5mmHg was 0.755 +/- 0.159MPa. There was no significant difference between the two visits (paired t-tests: p>0.05). The repeatability [1.96 times the standard deviation (S.D.) of the intersession difference] of the corneal stiffness and the tangent elastic modulus was 0.0022Nmm(-1) and 0.197MPa, respectively. ConclusionThe corneal indentation device has good intrasession and intersession repeatability. It has good potential to measure corneal biomechanics clinically, even at different corneal regions.