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I.J. Kelly, N.J. L. Sheen, J.E. Morgan, D.R. Owens, J.M. Wild, R.V. North; REPRODUCIBILITY OF MACULAR IMAGES USING THE HRT II SCANNING LASER OPHTHALMOSCOPE AND THE INFLUENCE OF ASTIGMATISM ON THE Z PROFILE SIGNAL WIDTH. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2994.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To (i) evaluate the reproducibility of Z profile based retinal thickness estimation using the HRT II macula oedema software, (ii) determine the effect of astigmatic correction on measurements derived from the macula oedema software. Methods: 24 normal healthy eyes from subjects aged 20–30 years were imaged through undilated pupils at a working distance of 10mm. To assess repeatability of the HRT II the following groups were imaged (7 images per subject) as follows: (i) Group A, 7 eyes with minimal astigmatism (mean 0.21DC, range 0 – 0.50DC). (ii) Group B, 7 eyes with moderate astigmatism (mean 1.39DC, range 0.75 – 1.75DC) corrected using cylindrical lenses provided by the manufacturer. To assess the influence of uncorrected astigmatism, ten eyes (Group C) with greater than 0.50DC of astigmatism (mean 1.20DC, range 0.75–1.75DC) were imaged three times with, and without, astigmatic correction with the cylindrical lenses. All images for the three groups were analysed with the Heidelberg Macula Edema Module Version 1.1.0. A circle contour 2mm in diameter was drawn on each image, centred on the fovea, and the mean Z profile signal width within this circle was recorded for all scans. Results: The mean COV for Z profile signal width for Group A was 8.62% (SD 4.32) and 9.19% (SD 4.23) for Group B. No significant difference was found in Z profile signal width measurements within eyes for Group A, p = 0.192, or for Group B, p = 0.277 (ANOVA). Mean Z profile signal width was found to be significantly increased when eyes in Group C were imaged without astigmatic correction, p < 0.05 (paired T–test). Conclusions: There is good repeatability for Z profile signal width measurements using the HRT II and it is not affected by the correction of astigmatism with the Heidelberg cylindrical lenses. The Z profile signal width is significantly increased with astigmatism greater than 0.50DC. When imaging the macula using the HRT II, astigmatism greater than 0.50DC requires correction. This information is of importance when imaging macular oedema in conditions such as diabetes mellitus. CR: None Support: The BUPA Foundation
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