METHODOLOGY FOR RETINAL PHOTOGRAPHY AND ASSESSMENT OF DIABETIC-RETINOPATHY - THE EURODIAB IDDM COMPLICATIONS STUDY

We present the methodology for 45 degrees retinal photography and deta il the development, application and validation of a new system of 45 d egrees field grading standards for the assessment of diabetic retinopa thy. The systems were developed for the EURO-DIAB IDDM Complications S tudy, part of a European Community funded Concerted Action Programme i nto the epidemiology and prevention of diabetes (EURODIAB). Assessment of diabetic retinopathy was carried out centrally by a trained reader of colour retinal photographs using the newly-developed system. The s ystem proved to be acceptably accurate, repeatable and relatively simp le to apply. It compared well with the recognised 'gold standard' 7-fi eld 30 degrees stereo photography (assessed using a modified Airlie Ho use classification scheme), against which the new system was validated in a series of 48 eyes. Selection was as a stratified random sample b ased on clinical retinopathy status: 5, no retinopathy; 25, non-prolif erative retinopathy; 16, proliferative or photocoagulated; plus 2, eye s with potentially confounding lesions (vein occlusion). Simple presen ce of retinal lesions was correctly detected by both systems in 43 of the 48 eyes, giving 100 % agreement on detection. Both systems correct ly identified the two known cases of confounding vein occlusion. In ey es with diabetic retinopathy (n = 41), when severity was expressed in three groups: mild background, moderate/severe background and prolifer ative/ photocoagulated, at least one grader (out of five) using the ne w system matched the verified results in 38 out of 41 (93 %) eyes and three or more graders matched in 31 (76 %) eyes. Individually the five graders' 2-field allocations agreed well with the verified levels (me dian number of agreements 37, range 28-43). Repeatability was assessed by measures of within and between observer variation using randomly s elected samples of 10 % (n = 252 eyes) and 5 % (n = 123 eyes) of the m ain study, respectively, expressed as a resultant kappa value for chan ce-corrected proportional agreement. Within observer assessment yielde d a kappa of 0.85 and between observers a value of 0.83 indicating ver y good agreement for both measures. The method is particularly useful for large epidemiological studies, in which participating centres have a limited experience in retinal photography.