Detection of diabetic retinopathy: a comparison between red-free digital images and colour transparencies.
BACKGROUND
The aim of this study was to compare how diabetic retinopathy was detected from red-free digital images and colour transparencies.


METHODS
Two ophthalmologists graded two-field, nonstereoscopic, 60 degrees red-free digital images and colour transparencies utilizing an ETDRS-based grading scale, from 107 mainly type 2 diabetic patients. The discordantly scored eyes were graded by the graders together to obtain a consensus level of retinopathy for each method. The eyes with discordant consensus grading results were further graded using all available photographic material to reach a final consensus level of diabetic retinopathy. Intermethod variations were presented as percentages and using kappa (k) and weighted kappa (wk) statistics. The errors of the two consensus gradings with respect to the final consensus grading were compared using McNemar's test.


RESULTS
For the colour transparencies there was an agreement between the individual and the consensus grading results in 93% (k=0.90, wk=0.97) and 86% (k=0.79, wk 0.88) for grader 1 and grader 2. Corresponding figures for red-free digital images were 88% (k=0.83, wk=0.96) and 84% (k=0.78, wk 0.91). Agreement between methods was obtained in 76/107 eyes (71%; k=0.58 and wk=0.79). In the 31 discordantly graded eyes the level of retinopathy was underestimated in 20/31 (64%) vs 7/31 eyes (23%) and overestimated in 1/31 (3%) vs 3/31 eyes (10%) from colour transparencies and red-free digital images, respectively. The error tendencies were significantly lower when using red-free digital images (p<0.008).


CONCLUSIONS
Red-free digital images are comparable with two-field colour transparencies in the identification of mild to moderate nonproliferative diabetic retinopathy.
von Wendt
Gunvor
G
Department of Vitreoretinal Diseases, St Eriks Eye Hospital, Polhemsgatan 50, 112 82, Stockholm, Sweden. gunvor.von.wendt@sankterik.se
Summanen
Paula
P
Hallnäs
Kerstin
K
Algvere
Peep
P
Heikkilä
Kauko
K
Seregard
Stefan
S
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003930:Diabetic Retinopathy / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010781:Photography / Q000379:methods*; D015203:Reproducibility of Results
Acta Ophthalmol Scand. 1999 Dec;77(6):638-47
10634555
Graefes Arch Clin Exp Ophthalmol. 1996 Aug;234 Suppl 1:S13-7
8871144
Am J Ophthalmol. 2002 Aug;134(2):261-3
12140033
Diabet Med. 2003 Jul;20(7):528-34
12823232
Acta Ophthalmol Scand. 2000 Apr;78(2):164-8
10794249
Am J Ophthalmol. 2002 Aug;134(2):204-13
12140027
Acta Ophthalmol Scand. 2002 Aug;80(4):372-8
12190778
Can J Ophthalmol. 2001 Jun;36(4):187-96
11428527
Diabet Med. 1998 Mar;15(3):250-3
9545127
Diabetes Care. 2000 Mar;23(3):345-8
10868863
Ophthalmology. 2002 Mar;109(3):595-601
11874767
Biometrics. 1977 Mar;33(1):159-74
843571
Acta Ophthalmol Scand. 2000 Feb;78(1):14-20
10726781
Ophthalmology. 1991 May;98(5 Suppl):823-33
2062515