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Repeatability and reproducibility of corneal biomechanical measurement with dynamic Scheimpflug Analyzer in virgin and post-PRK eyes
Session Title: Corneal biomechanics
Session Date/Time: Tuesday 08/10/2013 | 08:00-10:30
Paper Time: 09:20
Venue: Elicium 1 (First Floor)
First Author: : X.Chen NORWAY
Co Author(s): : A. Stojanovic Y. Hua J. Wang T. Jiang T. Zhang T.
To determine if the corneal biomechanical response measurements obtained by Corvis®ST, a dynamic Scheimpflug analyzer, can be reliably repeated and reproduced in virgin and post-PRK eyes.
SynsLaser Clinic, Norway
The Corvis ST utilizes ultra-high speed Scheimpflug camera to record the horizontal corneal deformation under an air puff indentation. Twenty-one right virgin eyes and 30 post-PRK right eyes underwent Corvis®ST measurement performed by two technicians. Repeatability was evaluated by comparing three consecutive measurements by technician A. Reproducibility was determined by comparing the first measurement by technician A with the one performed by technician B. Intraobserver and interobserver intraclass correlation coefficient (ICC), within-subject coefficient of variation (COV), and within-subject standard deviation (Sw) were calculated.
The most repeatable and reproducible parameters were intraocular pressure ([IOP], virgin/post-PRK group: ICC 0.947/0.895 and 0.928/0.895; COV 4.09%/4.43% and 4.15%/4.07%; Sw 0.58/0.54 and 0.59/0.50 for repeatability and reproducibility, respectively); central corneal thickness ([CCT], virgin/post-PRK group ICC 0.985/0.981 and 0.984/0.895; COV 1.01%/1.99% and 0.88%/0.80%; Sw 5.39/9.43 and 4.72/3.84), 1st applanation time ([A1T], virgin/post-PRK group ICC 0.952/0.895 and 0.948/0.900; COV 1.16%/1.29% and 1.09%/1.23%; Sw 0.08/0.09 and 0.08/0.08), 2nd applanation time ([A2T], virgin/post-PRK group ICC 0.927/0.808 and 0.882/0.725; COV 0.80%/0.83% and 0.82%/0.92%; Sw 0.17/0.18 and 0.18/0.20), and deformation amplitude ([DA], virgin/post-PRK group ICC 0.924/0.883 and 0.916/0.870; COV 3.84%/3.43% and 3.67%/3.51%; Sw 0.04/0.04 and 0.04/0.04). The other parameters showed poor repeatability and reproducibility. Comparing the measurement results of the two groups, the virgin eyes showed higher IOP, CCT, A1T values, and lower A2T and DA values, compared to the post-PRK group. IOP correlated positively with CCT and A1T, and negatively with A2T and DA in both groups.
Corvis®ST demonstrated repeatable and reproducible measurements for IOP, CCT, A1T, A2T and DA. The measurement results in virgin eyes and post-PRK eyes differed in most of these parameters.