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D. Descovich, M.-H. Roy-Gagnon, P. St-Onge, M. Lesk; Reproducibility of Pulsatile Ocular Measurements, IOP and Choroidal Blood Flow, and of Corneal Hysteresis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5866.
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© ARVO (1962-2015); The Authors (2016-present)
Pulsatile phenomena in the eye can be used to estimate ocular rigidity using the Freidenwald Equation. We studied the reproducibility of ocular IOP pulse amplitude (OPA) and of the pulsatility of choroidal blood flowmetry measurements. We also studied the reproducibility of a direct measure of corneal biomechanical properties, corneal hysteresis.
32 subjects (16 normals and 16 open angle glaucoma) had repeated measures one hour apart. OPA was determined with the Pascal Dynamic Contour Tonometer. Choroidal blood velocity (VEL), volume (VOL) and flow (FLO) were measured in the sub-foveolar choroid using single-point laser Doppler flowmetry (Oculix). The pulsatility of VEL, VOL and FLO was determined with automated software using, for example, the formula (systolic VEL- diastolic VEL) / systolic VEL. Corneal hysteresis was determined using the Reichert Ocular Response Analyser (ORA). For each parameter, we first examined reliability graphically using a scatter diagram and a Bland-Altman plot. We then calculated the intraclass correlation coefficient (ICC) with bootstrap 95% confidence interval (CI) as well as the coefficient of variability (CV).
The ICC of OPA was 0.84 (95% CI: 0.73 - 0.92). The ICCs of the pulsatility of choroidal flowmetry were: VEL: 0.79 (0.65 - 0.88); VOL: -0.06 (-0.45 - 0.39); FLO: 0.80 (0.65 - 0.89). The ICC of CH was 0.81 (CI 0.60 - 0.91). CVs were between 6.5 and 10.6% for all parameters except VOL (20.6%).For comparison purposes, the ICC and CV for mean IOP as measured with the Pascal were 0.91 (0.84 - 0.95) and 3.3%, while they were 0.87 (0.73 - 0.94) and 5.4% for IOPg measured with the ORA.
For pulsatile choroidal flowmety, reproducibility was better for VEL and FLO than for VOL. OPA and CH had good reproducibility. These parameters can be used to develop new estimates of ocular biomechanical properties.
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