Can digitised colour 35 mm transparencies be used to diagnose diabetic retinopathy?

Retinal photography is an adjunct to ophthalmoscopy in screening for diabetic retinopathy (DR). Digital retinal cameras allow a retinal image to be displayed immediately on a high resolution video display monitor. We conducted a pilot study to investigate the agreement in retinopathy grading from digitized images in comparison to original colour transparencies as 35 mm slides. One hundred and fifty macula-centred, 45 degree, non-stereoscopic retinal images were digitized onto CD ROM by Kodak at base resolution of 768 x 512 pixels. The anonymized images were displayed on a 17" monitor running Windows at 800 x 600 resolution in 64,000 colours (PC images) and graded in random order. Alternatively the transparencies were graded on a Slidex viewer. A quality control set were also graded with exact agreement in 93% of cases (91% (73/80) of PC images and 94% (75/80) of slide images). Compared to colour transparencies, 95% (84/88) of sight threatening diabetic retinopathy (STDR) and 100% (62/62) of non-STDR cases were diagnosed using the PC. One case of pre-proliferative DR and three cases of non-proliferative DR were graded as non-STDR from the PC. There was good agreement between PC displayed digitized retinal images and 35 mm colour transparencies.