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T Farra, E Hertzmark, JS Schuman; The Correction of HRT Parameters for Scan Angle . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3412.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To find a correction factor for the HRT global parameters that are affected by scan angle. Methods: The sample consisted of 10 normal subjects. One eye of each subject was randomly selected and 3 scanning laser tomography images were taken using the Heidelberg Retinal Tomograph at each of 10, 15 and 20 degree scan angles. Topographic images were generated using software version 2.01. For each subject, a contour line was drawn on the first image, and was imported to the rest of the images for that subject. Optic nerve head global parameters were calculated using the standard reference height. The parameters were analyzed using a repeated measures regression with scan angle treated as a continuous variable. Correlation coefficients were calculated for each parameter affected by scan angle. Results: The relationships between the affected measures and scan angle are shown in the table below. View OriginalDownload SlideView OriginalDownload Slide Conclusion: In the longitudinal analysis of HRT parameters, disc area, mean radius, effective area, volume above surface, mean cup depth, cup shape, and mean height of contour must be corrected if images taken at different scan angles are being compared.
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