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N. Gupta, K. L. Fry, B. L. Tannen, P. S. Hersh; Normal Values and Variability of Central Corneal Thickness and Biomechanical Parameters. Invest. Ophthalmol. Vis. Sci. 2008;49(13):644.
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To determine values and variability for central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF)
Retrospective chart review was carried out on 1316 eyes that presented for refractive surgery. CCT was measured using ultrasound pachymetry. Biomechanical measures of CH and CRF were obtained using the Ocular Response Analyzer. CCT was stratified by patient age and manifest refraction spherical equivalent (MRSE). CH and CRF were stratified by age, refraction and CCT. Age was grouped into decades. MSRE was grouped into 3-diopter intervals. Statistical analysis was performed to evaluate potential correlations between subgroups.
Mean patient age was 39.8 years (SD 12.3; range 18 to 80). Mean MRSE was -3.94 diopters (SD 3.34; range -16.25 to 5.25). Mean CCT was 542.4 microns (SD 33.5; range 415.0 to 695.0). Mean CH was 10.6 mmHg (SD 1.78; range 3.7 to 17.5) and mean CRF was 10.3 mmHg (SD 1.89; range 2.5 to 17.3).There was no statistically significant difference in CCT among patients grouped by age or MRSE. Likewise, CH and CRF stratified by age and MRSE showed no statistical difference among subgroups. CH and CRF were positively correlated with CCT (lower CH and CRF values were observed in eyes with thinner CCT).
Although CCT does not statistically vary by age or MRSE, a positive relationship exits between CCT and CH and CRF. Normative values for CCT, CH and CRF may identify outliers requiring further investigation, particularly in screening patients for refractive surgery.
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