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N. Bourla, N. Lee, D. R. Hamilton; Biomechanical Measurements in Corneal Ectatic Disorders. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1850.
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Patients with corneal ectatic disorders possess impaired corneal biomechanics. The Ocular Response Analyzer (Reichert) measures the biomechanical metrics corneal hysteresis (CH) and corneal resistance factor (CRF). This study compares CH and CRF measurements in ectatic corneas (e.g. keratoconus, pellucid marginal degeneration, post-LASIK ectasia) with normal corneas.
CH and CRF were measured for 141 eyes in two groups. Group 1 consists of 97 eyes defined as normal based on clinical and topographic findings. Group 2 consists of 44 eyes defined as ectatic based on clinical and topographic findings (26 eyes with keratoconus, 8 eyes with pellucid marginal degeneration, and 10 eyes with post-LASIK ectasia). Statistical analysis was performed to examine differences between groups.
Both CH and CRF measurements were significantly lower in eyes with ectatic disorders (7.09+1.65, 7.61+1.24, respectively) compared with normal eyes (11.25+1.56 and 11.52+1.66 respectively, P < 0.001). No significant difference in CH and CRF values was found between the keratoconus, pellucid marginal degeneration and post-LASIK ectasia eyes.
The CH and CRF measurements in eyes with corneal ectatic disorders are significantly lower when compared to eyes with normal corneas. The biomechanical metrics CH and CRF may assist with the identification of abnormal corneas and allow for quantification of biomechanical differences between normal and ectactic corneas.
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