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R. A. Stone, G.-S. Ying, D. Pearson, M. Bansal, M. Puri, the CODA Study Group; Utility of Stereo Digital Images for Optic Disc Evaluation. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5808.
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© ARVO (1962-2015); The Authors (2016-present)
To assess digital stereo optic disc images as a reference standard for glaucoma.
We acquired contemporaneous stereo color optic disc images in both digital (OIS Winstation 5000; 4.9 megapixel camera) and 35mm slide (Fuji Velvia) formats from 29 subjects with various cup:disc ratios (range 0.26-0.76; median 0.475). Using a high resolution, broad gamut, regularly calibrated NEC MultiSync digital monitor, the primary digital stereo images were separately compared to each subject’s 35mm slides, to scanned images of the same 35mm slides (Nikon 5000 ED scanner; SilverFast Ai software) and to gray scale conversions of the digital images (Photoshop channels mixer: G-85%; B-15%). The digital image sets to be compared were mounted in Photoshop on a black background as stereo pairs, one above the other. Four experienced observers compared the stereo image sets using a 5-point scale for 18 criteria designed to assess image quality, the ease of defining optic disc features important for glaucoma and the comparative diameters of the optic cup. Statistics accounted for multiple grading of the same images (GEE) and multiple comparisons (Bonferroni).
Overall, the quality of primary digital color images was judged superior to 35mm slides, including improved stereo (p<0.001), and superior to scanned digitized images of the same slides for some criteria (p<0.001). In defining optic disc features, the primary digital images were judged better than 35mm slides for most criteria (p≤0.002) but equivalent to the scanned images of the slides. Color digital images were largely equivalent to their gray scale conversions except that peripapillary atrophy was best seen in color (p<0.0001) and the nerve fiber layer, in gray scale (p<0.0001). Stratifying images as greater or less than the median cup:disc ratio resulted in minor differences in the grading. Image format had little impact on comparative assessments of the optic cup diameters.
Digital images are replacing film in ophthalmic photography. Digital stereo optic disc images are useful for evaluating the optic disc and can be substituted as the "gold standard" of film images in observer assessments for glaucoma.
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