Sensitivity and specificity of photography and direct ophthalmoscopy in screening for sight threatening eye disease: the Liverpool diabetic eye study

Abstract

Objective: To evaluate different methods for community based screening for sight threatening diabetic eye disease. Design: Prospective study. Setting: Mobile screening unit visiting inner city community clinics; hospital assessment clinic (tertiary centre). Subjects: 395 diabetic patients registered with four general practices in an inner city location. Interventions: Community based photography with mydriasis and direct ophthalmoscopy through dilated pupils by an experienced ophthalmologist, both compared with reference standard of slit lamp biomicroscopy by a consultant specialist in medical retinal disease. Main outcome measures: Sensitivity and specificity of screening method and prevalence of sight threatening diabetic eye disease (moderate preproliferative retinopathy, circinate maculopathy, exudate within 1 disc diameter of fixation, other diabetes related eye disease). Results: 358 subjects underwent photography, 326 attended hospital clinic for ophthalmoscopy, and six were ungradable on photographs and biomicroscopy, leaving 320 for analysis. Of these 295 (91%) attended clinic within four months of photography. Sensitivity of detection of eye disease by photography was 89% (95% confidence interval 80% to 98%), significantly better than for direct ophthalmoscopy (65% (51% to 79%)). Analysis of patients with false negative results indicated possible improvement of photographic sensitivity to 93% by addition of stereoscopic macular pair photographs. Specificity of detection of sight threatening eye disease was 86% (82% to 90%) for photography and 97% (95% to 99%) for direct ophthalmoscopy. Conclusions: Since high sensitivity is essential for an effective screening programme, a photographic method should be considered as preferred option in national, community based screening programmes. Even in the hands of an experienced ophthalmologist, direct ophthalmoscopy is limited by weaknesses inherent to the instrument.