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Maxime Delbarre, Mikhael Lussato, Bénédicte Blavier, Corine Leduc, Pascale Crepy, Françoise Froussart-Maille, Jean Claude Rigal-Sastourné; Delay Between The Inward And The Outward Signal Peaks Of The Ocular Response AnalyserTM In Normal And Keratoconic Eyes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5171.
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Compare the delay between the inward and the outward signal peaks extracted from the signal curves of the ocular response analyser (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA) in keratoconic eyes and in a control group.
This retrospective, comparative study included every patients with unilateral or bilateral keratoconus examined in our center between January 2008 and June 2010. This serie included 23 patients with keratoconus and 54 age- and sex- matched controls who underwent a complete clinical eye examination, corneal topography, and biomechanical evaluation. Every patient was subjected to examination (between 3 and 5 measures/per eye) by the ORA. Corneal hysteresis (CH), corneal resistance factor (CRF), and time duration between « in » and « out » signal peaks were compared between the two groups.
Corneal hysteresis was 8.58+/- 1.82 mmHg (range: 5.21 to 17.1 mmHg) in the keratoconus group and 10.54+/- 1.81mmHg (range: 2.7 to 22.1 mmHg) in the control group (P<0.001). Corneal resistance factor was 7.59+/- 2.06 mmHg (range: 4.1 to 15.1 mmHg) in the keratoconus group and 10.6 +/- 2.03 mmHg (range: 4.10 to 23.70 mmHg) in the control group (P<0.001). Time duration between « in » and « out » signal peaks was 11.36+/- 0.70 ms (range: 9.9 to 14.5 ms) in the keratoconus group and 10.82+/- 0.51 ms (range: 8.7 to 12.6 ms) in the control group (P<0.001).
Corneal hysteresis and corneal resistance factor were statistically lower in the keratoconus group compared with the control group as it was already showed in former studies. Time duration between "in" and "out" signal peaks is statistically significantly higher in the keratoconus group. This is a new data on the evaluation of corneal biomechanical properties.
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