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T. M. Harding, J. F. Florez-Arango, L. D. Hubbard, R. P. Danis, A. E. Mosher, M. K. Swift, D. P. Murach, H. K. Li; Mosaic of Wide-Angle Digital Color Images vs. ETDRS Stereo 7 Field Images for Grading Diabetic Retinopathy Severity. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2737.
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© ARVO (1962-2015); The Authors (2016-present)
To compare diabetic retinopathy (DR) severity levels graded from mosaicked 9-field, wide-angle, digital color retinal images to those graded from standard ETDRS 7-field stereo 35o color images, both digital and film.
Selected for a full range of diabetic retinopathy, 141 eyes of diabetic persons were imaged with two different protocols. Nine 45o color monoscopic fields (M9 - disc/macula surrounded by 8 peripheral views) were taken with Topcon TRC-NW6S (10.1 megapixels, 3008x2000 pixels), and auto-mosaicked with IMAGEnet (3564x3600 pixels). To preserve detail, adjoining edges were not smoothed. Seven color stereo 35o fields (7SF per ETDRS) were taken with Topcon TRC-50EX/IX, both digital (D7SF - 6 megapixel sensor, 2392x2048 pixel image, uncompressed) and film (F7SF) . Three graders determined ETDRS DR level on calibrated 20" LCD monitors from M9 and D7SF (the latter with hand-held stereo viewers). Image tonal parameters were enhanced according to the AREDS2 image model, and images examined also in green-channel breakout. DR was graded from F7SF using slides on light boxes with Donaldson viewers. Order and timing of evaluations were controlled by software to minimize recall. DR levels within each medium were defined by central tendency among graders.
From FSF images, graders classified DR as follows: no DR = 24 eyes; non-proliferative DR (NPDR) = 88 eyes (microaneurysms only/mild/moderate/severe = 6/32/23/27); and proliferative DR (PDR) = 29 eyes (mild/moderate/severe = 9/10/10). Comparing M9 to both F7SF/D7SF for specific ETDRS level (9-step scale) yielded the following agreement: exact, 65.2%/68.8% - unweighted Κ = 0.60/0.63 (SEΚ ≤ 0.05); +1 step, 85.8%/97.9 - linear weighted Κ - 0.83/0.86 (SEΚ = 0.03). For comparison, agreement between F7SF and D7SF was 66.7% exact (unweighted Κ = 0.61 [SEΚ = 0.03]), and 95.7% +1 step (linear weighted Κ = 0.86 [SEΚ = 0.02]). Comparing M9 to F7SF for 1-step DR difference in 42 eyes, M9 was higher in 30 and 7SF was higher in 12.
Nine-field wide-angle digital color mosaics appeared comparable to both F and D 7SF for DR severity grading, although in disagreements M9 tended to be higher than F7SF (former captures more retina). Practical advantages of M9 are fewer flashes for the patient (9 vs. 14 for 7SF), and more economical file transmission/storage.
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