Colour slides or digital photography in diabetes screening – a comparison
The aim of this study was to compare digital images with slides in detecting and grading diabetic retinopathy, and to assess the retinopathy screening performed by ophthalmic nurses.
283 consecutive patients were examined using digital colour and redfree photography (Topcon Imagenet System 1.53) and 35 mm slides (Topcon TRC-50 VT fundus camera, Kodachrome 64 colour film). The images were graded by the worst eye according to the Wisconsin classification by an ophthalmologist and ophthalmic nurse independently.
There was exact agreement between grades obtained from the colour slides and the digital colour images in 82% (weighted kappa 0.88; 95% CI 0.80–0.96), and in 85% when redfree images were used as an adjunct to the digital colour images. There was a tendency towards undergrading of the digital colour images and overgrading of the digital redfree images, compared with the colour slides. Inter- and intragrader agreement (weighted kappa) varied between 0.77 and 0.84 for digital photography and between 0.88 and 0.90 for colour slides.
Good to excellent agreement was found between the grading of colour slides and digital colour images, the latter, however, associated with a slightly lower reliability. The adjunct of redfree images seemed to facilitate the detection of retinopathic lesions.