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C. Samarawickrama, S. C. Huynh, G. Burlutsky, J. B. Jonas, P. Mitchell, Sydney Childhood Eye Study, Sydney Myopia Study; Correlation of Optic Disc Parameters Measured by Digital Retinal Photographs and Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):636.
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© ARVO (1962-2015); The Authors (2016-present)
To compare measurements of optic disc parameters assessed from digital photographic images and from optical coherence tomography (OCT) in normal children.
The Sydney Childhood Eye Study assessed 1740 6-year old children from 34 randomly selected primary schools during 2003-5. Digital retinal images were acquired using a Canon fundus camera (CF-60Uvi)/ EOS 10D. Optic disc parameters were measured from these digital images using the Image J program. Optic disc parameters were acquired from OCT3 (Stratus) images using the "fast" optic disc protocol. To date, retinal images of 320 children have been graded by both methods and are included in the analyses. Optic disc and cup area, vertical and horizontal disc and cup diameters as well as cup/disc ratios were calculated using both modalities. The magnification by the optic media was corrected using appropriate formulae.
The mean vertical and horizontal disc and cup diameters and the mean disc and cup areas as measured by OCT (1.76, 1.50, 0.71 and 0.68mm and 2.15 and 0.47mm2, respectively) were significantly (P<0.0001) lower than those measured by digital fundus photography (1.89, 1.70, 0.77 and 0.76mm and 2.51 and 0.53mm2, respectively). The vertical and horizontal cup/disc diameter ratios and the cup/disc area ratio did not vary significantly (P>0.05) between the 2 methods (0.41, 0.45 and 0.22 versus 0.41, 0.44 and 0.21, respectively). All parameters were strongly correlated for both modalities (r≥0.50, p<0.0001) with the exception of vertical disc diameter, which was least correlated (r=0.20, p=0.0003) followed by horizontal disc diameter (r=0.38, p<0.0001).
Linear optic disc measurements of children are about 10% smaller when measured using OCT than by planimetry of fundus photographs, depending on the methods used for correcting the magnification of fundus images by the optic media. Since the ratios of measurements such as the cup/disc ratio did not differ between both methods, the differences in primary measurements between them may be mainly due to differences in correction of the magnification rather than differences in the definition and outlining of the disc structures.
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