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 µm vs 243.04 µm, P=0.03) and outer retina (124.26 µm vs 123.08 µm, P=0.01) than eyes without DR. When stratified by DR severity, thicker macula (250.24 µm vs 242.88 µm, P=0.011) and outer retina (126.4 µm vs 123.0 μm, 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.
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WD and YCT contributed equally.
Contributors WD and YCT: substantial contributions to the analysis and interpretation of data, drafting the work and revising it critically for important intellectual content and final approval of version to be published. NC, MY, NYQT, C-YC, JJW, PM, CS and TYW: substantial contributions to analysis and interpretation of data, revising the article critically for important intellectual content and final approval of version to be published. C-YC: substantial contributions to the conception and design of study, analysis and interpretation of data, revising the article critically for important intellectual content and final approval of version to be published and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Funding This work was supported by grants from Agency for Science, Technology and Research (grant number: 08/1/35/19/550) and National Medical Research Council (grant numbers: NMRC/1249/2010 and NMRC/CIRG/1371/2013).
Competing interests None declared.
Patient consent Obtained.
Ethics approval Singapore Eye Research Institute Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.