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Yao Nie, Qienyuan Zhou, Ben Jang, Danny Leung; Repeatability and Reproducibility of Central Corneal Power Measurement Using RTVue FD-OCT System. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4179.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the repeatability and reproducibility across instruments of central corneal power (CCP) measurement using RTVue with CAM (Optovue, Fremont, CA) and the impact of pupil alignment and fixation.
The study was conducted with 4 RTVue instruments, 10 subjects, and 1 operator, following an IRB approved study protocol. One eye per subject was randomly selected for the study. To evaluate repeatability and reproducibility, 3 CCP scans were acquired on each of the 4 RTVue instruments for each of the 10 study eyes with alignment centered on pupil and subject fixated on the fixation target center. To evaluate impact of pupil alignment and fixation, 3 CCP scans were acquired per test eye on one randomly selected instrument for 3 pupil alignment positions (central, offset-horizontally, and offset-vertically) with central fixation and for 3 fixation positions (central, offset-horizontally, and offset-vertically) with central pupil alignment. Variance components were calculated to assess repeatability and reproducibility. ANOVA model was used to compare central vs. offset pupil alignment and fixation.
Total 120 CCP measurements were acquired for the repeatability and reproducibility assessment. Variance component due to subject is 2.2323 (97.7%), variance component due to instrument is 0.008483 (0.4%), and residual variance is 0.04352 (1.9%); therefore, the repeatability is 0.209D (SD) and the reproducibility is 0.228D (SD). Ninety (90) CCP measurements were acquired for assessing pupil alignment and fixation impact respectively. With pupil shifted by approximately its radius horizontally or vertically, the measured CCP is reduced by approximately 0.2D on average, which is statistically significant (p<0.025). With fixation shifted from the center to the edge of the fixation target horizontally or vertically, the measured CCP is reduced by approximately 0.18D on average, which is statistically significant (p<0.004).
CCP measurement with RTVue is repeatable and reproducible across instruments. Pupil alignment and fixation could affect the measurement and operator should pay attention to the two factors during data acquisition.
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