Studies that assessed the accuracy of photography or examination-based retinopathy screening (in patients with diabetes or diabetic retinopathy) were eligible for inclusion. Studies measured sensitivity and specificity for the detection of diabetic retinopathy, sight-threatening diabetic retinopathy or macular oedema using either seven-field mydriatic photography or dilated fundus examination (by an ophthalmologist or equivalent specialist) as the reference standard. Studies of automated analysis methods were excluded.
Approximately half of the included studies were conducted in Europe; most of the others were conducted in the USA or Canada. Study settings were primary healthcare, diabetes clinics or hospitals. The mean age of study participants was 58 years (range 48 to 68.8 years). The mean proportion of male participants was 55.2% (range 31% to 98.4%). The mean duration of diabetes was 10.9 years (range 3.7 to 17.7 years).
Screening methods assessed were: digital photography; film photography; direct examination; Polaroid photography; various combinations of camera types or camera plus examination and scanning laser ophthalmoscope. Most assessments used pharmacological mydriasis in some or all participants. For the camera methods, single-field photography was most common and images were most frequently taken by a photographer or technician and interpreted by an ophthalmologist. Most assessments used dilated fundus examination as the reference standard.
Two reviewers independently screened studies for inclusion; disagreements were resolved by consensus or by consultation with an ophthalmologist.