Early microvascular and neuro-retinal alterations in type 2 diabetic patients without diabetic retinopathy

Purposeto evaluate and correlate the alterations of microvascular and chorioretinal structure in Type 2 diabetes mellitus (T2DM) patients without clinical signs of DR. MethodsT2DM patients were randomized sampled from Guangzhou Diabetic Eye Study and healthy controls from the community of Guangzhou, China were recruited in this cross-sectional study. Demographic, clinical and ocular parameters were regularly obtained. Retinal thickness (RT), retinal nerve fiber layer (RNFL) thickness, ganglion cell-inner plexiform layer (GC-IPL) thickness, outer retina layer (ORL) thickness and choroid thickness (CT) were automatically evaluated by swept-source optical coherence tomography (SS-OCT) in the 1, 3, and 6 mm centered on fovea. Vessel density (VD) was obtained by OCT angiography (OCTA) in the 1 and 3 mm centered on the fovea. Results1,444 eyes of 1,444 individuals (722 T2DM patients and 722 healthy controls) were included in the final analyses. Macular average RNFL was thinned (P < 0.001), average GC-IPL was thickened (P < 0.001), and ORL was thickened (P = 0.012) in DM patients compared with healthy controls independent of confounding factors. VD was significantly increased in diabetic patients without DR. Correlations were found between VD and specific layers of retina both in DM patients and in healthy controls. Especially in DM patients, average RT in positively related with parafoveal VD ({beta}= 0.010, 95%CI: 0.003 to 0.017) and total average VD ({beta}= 0.010,95%CI: 0.003 to 0.016). Specifically, RNFL thickness is inversely related with VD, while both GC-IPL and ORL thickness are positively related with VD in diabetic patients without DR. ConclusionThis study reports and correlates the early alterations of chorioretinal structure and retinal superficial vessels in T2DM patients even before the onset of clinical signs of DR. Findings of this study may provide novel insights to explore the pathogenesis of DR.