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A. Kotecha, D. Sinapis, A. Sinapis, D. F. Garway-Heath; Factors Affecting Corneal Biomechanics Measured With the Ocular Response Analyzer - Interim Analysis. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5554. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The Reichert Ocular Response Analyzer (ORA; Reichert Inc, USA) generates 2 measures of corneal biomechanics: corneal hysteresis (CH), a measure of the viscous dampening properties of the cornea, and the corneal response factor (CRF) which is thought to more reflect corneal elastic properties. The purpose of this study was to explore parameters associated with CH and CRF.
One hundred and forty eight eyes of 148 (of a target 240) participants (average age 46, range 19 to 80, standard deviation 20 years) with no ocular pathology were examined. Each eye had three ORA measurements and the average CH and CRF were used in the analysis. Axial length (AL) and keratometry (K) measurements were made using the IOL Master. The Pascal dynamic contour tonometer (DCT; Swiss Microtechnology AG, Switzerland) is thought to be less affected by variations in corneal biomechanics and thus was used as a surrogate measure of IOP. Parameters explored included age, DCT IOP, central corneal thickness (CCT), AL and K. Data were analysed using MedCalc version 10.3.2.0.
Multiple regression analysis showed that of the factors explored, only age and CCT were significantly associated with CH ( -0.24 mmHg reduction CH per decade advancing age, r = -0.21, p = 0.0003; 0.21 mmHg increase CH per 10 micron increase CCT, r = 0.35, p < 0.0001). Age, CCT and AL were significantly associated with CRF (-0.26 mmHg reduction CRF per decade, r = -0.21, p < 0.0001; 0.26 mmHg CRF increase per 10 micron increase CCT , r = 0.48, p < 0.0001; -0.29 mmHg reduction CRF per mm increase axial length, r = -0.19, p = 0.01).There were no associations between age and IOP or CCT.
These preliminary analyses indicate that both CH and CRF are positively associated with CCT and negatively associated with age. Our finding that CRF reduces with age agrees with other ORA studies, but is contradictory to experimental studies which show that the cornea becomes stiffer with advancing age. This suggests that the CRF may not be a measure of corneal elasticity. Further work is required to elucidate the ocular interactions that may explain this finding.
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