Macular thickness profile and diabetic retinopathy: the Singapore Epidemiology of Eye Diseases Study

Background To evaluate retinal thickness profiles in eyes with and without diabetic retinopathy (DR) using spectral-domain optical coherence tomography (SD-OCT) among individuals with diabetes. Methods Participants were recruited from the Singapore Epidemiology of Eye Diseases Study, a population-based study among Chinese, Malays and Indians aged 40 years or older residing in Singapore. All participants underwent standardised systemic and ophthalmic examinations. Average thickness of the macula, ganglion cell-inner plexiform layer and outer retina layer (from the outer plexiform layer to the retinal pigment epithelium layer) were measured using SD-OCT. DR status and severity were graded based on fundus photographs using the modified Airlie House classification system. Participants with macular oedema were excluded. Results 2240 eyes from 1280 participants were included. Of these, 1764 (78.7%) eyes had no DR, 351 (15.7%) eyes had minimal or mild DR and 125 (5.6%) eyes had moderate or worse DR. After adjusting for age, gender, ethnicity, axial length, hypertension, glycated haemoglobin, body mass index, total cholesterol and diabetes duration, eyes with DR had thicker macula (245.44 mu m vs 243.04 mu m, P=0.03) and outer retina (124.26 mu m vs 123.08 mu m, P=0.01) than eyes without DR. When stratified by DR severity, thicker macula (250.24 mu m vs 242.88 mu m, P=0.011) and outer retina (126.4 mu m vs 123.0 mu m, P=0.006) were observed in eyes with moderate or worse, but not minimal or mild DR, compared with eyes without DR. Conclusions Even in the absence of macular oedema, eyes with DR, particularly those with more severe DR, had thicker macular and outer retinal layers than eyes without DR.