Biomechanical Properties of the Cornea Using a Dynamic Scheimpflug Analyzer in Healthy Eyes

PURPOSE: To investigate biomechanical properties of the cornea using a dynamic Scheimpflug analyzer according to age. MATERIALS AND METHODS: In this prospective, cross-sectional, observational study, participants underwent ophthalmic investigations including corneal biomechanical properties, keratometric values, intraocular pressure (IOP), and manifest refraction spherical equivalent (MRSE). We determined the relationship of biomechanical parameters and ocular/systemic variables (participant's age, MRSE, IOP, and mean keratometric values) by piecewise regression analysis, association of biomechanical parameters with variables by Spearman's correlation and stepwise multiple regression analyses, and reference intervals (RI) by the bootstrap method. RESULTS: This study included 217 eyes of 118 participants (20–81 years of age). Piecewise regression analysis between Corvis-central corneal thickness (CCT) and participant's age revealed that the optimal cut-off value of age was 45 years. No clear breakpoints were detected between the corneal biomechanical parameters and MRSE, IOP, and mean keratometric values. Corneal velocity, deformation amplitude, radius, maximal concave power, Corvis-CCT, and Corvis-IOP exhibited correlations with IOP, regardless of age (all ages, 20–44 years, and over 44 years). With smaller deformation amplitude and corneal velocity as well as increased Corvis-IOP and Corvis-CCT, IOP became significantly increased. We provided the results of determination of confidence interval from RI data using bootstrap method in three separate age groups (all ages, 20–44 years, and over 44 years). CONCLUSION: We demonstrated multiple corneal biomechanical parameters according to age, and reported that the corneal biomechanical parameters are influenced by IOP.

Corneal biomechanical properties after femtosecond laser assisted LASIK with the corneal visualization Scheimpflug technology and ocular response analyzer / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To investigate the changes of corneal biomechanical properties before and after femtosecond laser assisted LASIK(FS-LASIK)using Corneal Visualisation Scheimpflug Technology(Corvis ST)and Ocular Response Analyzer(ORA), and the correlation with other myopic parameters. <p>METHODS:Sixty three patients(63 eyes)who had myopic femtosecond laser assisted LASIK(FS-LASIK)were enrolled in the study. The right eye of each patient was analyzed in this study. The corneal biomechanical parameters pre-operative and 1mo post-operative was measured with the Corvis ST(Oculus, Wetzlar, Germany)and ORA(Reichert, Buffalo, New York, USA). Comparison of the biomechanical property values before and after surgery was peformed using Paired <i>t</i>-test or Mann-Whitney <i>U</i>. Pearson or Spearman correlations were used to evaluate the relationship between parameters.<p>RESULTS: The postoperative 1^st A-time, Vin, 2^nd A length, Vout, HC time and Radius demonstrate significant decreases comparing with preoperative values(<i>P</i>=0.00, <i>P</i>=0.00, <i>P</i>=0.00, <i>P</i>=0.00, <i>P</i>=0.00, <i>P</i>=0.00 respectively). The postoperative 2^nd A-time, DA and PD significantly increases(<i>P</i>=0.00, <i>P</i>=0.00, <i>P</i>=0.00), however, the 1^st A length had no significant difference after surgery. The CH and CRF were significantly lower after FS-LASIK(<i>P</i>=0.00, <i>P</i>=0.00). A statistically significant correlation coefficient was found between preoperative central corneal thickness(CCT)with postoperative-preoperative changes of 1^st A-time, 2^nd A-time, DA and Radius respectively(<i>P</i>=0.01, <i>P</i>=0.04, <i>P</i>=0.03, <i>P</i>=0.01). <p>CONCLUSION:There were significantly changes of corneal biomechanical properties after FS-LASIK surgery. The changes of corneal biomechanical properties after FS-LASIK can be reflected by some parameters of Corvis ST and ORA. The mainly influence of corneal biomechanical alteration was possibly correlation with corneal thickness.