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Anna L. Moore, Ariba Bhuvad, Bhukhan Preeti, Sudhindra Gadagkar, Vladimir Yevseyenkov; Reliability of the iTrace Ray Tracing Wavefront Aberrometer and Corneal Topographer as an Indirect Measure of Contrast Sensitivity. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3597.
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To determine whether the iTrace ray tracing wavefront aberrometer and corneal topographer reliably measures contrast sensitivity and refractive error.
Twenty-five visually normal adults (n=50 eyes;mean age = 27.56 ± 3.2 years; age range 25-39 years), were tested on the iTrace ray tracing wavefront aberrometer and corneal topographer. Each measurement was repeated 3 times and testing was conducted uncorrected. All subjects had BCVA of 20/20 OD and OS and were free of any ocular pathology. Normal contrast sensitivity was verified utilizing subjective measurement MARS chart at a distance of 40 cm, with mean luminance of 85 cd/m2.
Test-retest reliability was confirmed utilizing Cronbach’s alpha analysis. Cronbach alpha for point spread function analysis was 0.912 OD and 0.886 OS, modulation transfer function was 0.936 for OD and 0.898 OS, Mean Root Square was .921 OD and .942 OS. Refractive status for sphere, cylinder and axis was also analyzed by Cronbach’s alpha analysis and all values were above 0.9 for both the right and left eyes. A 95% confidence interval for the mean of the point spread function ranged from 0.3116 to 0.4837 with an average of 0.392 , for modulation transfer function 0.47 to 0.572 with an average of 0.547 , and for root mean squared 3.43 to 4.00 with an average of 3.81.
Using Cronbach’s alpha analysis, we were able to confirm the reliability of the iTrace ray tracing wavefront aberrometer and corneal topographer to measure point spread function, modulation transfer function, and root mean square outputs, which are all indirect measurements of contrast sensitivity. Limits of agreement of 95% showed very little variation among normal adults, indicating that measurements of 0.392 for PSF, 0.547 for MTF, and 3.81 for RMS may be considered "normal" values and useful in comparison with a diseased population to determine contrast sensitivity loss.
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