Aims To investigate the function and the corresponding neurovascular structures in patients with diabetes without clinically detectable retinopathy. Methods Sixty-six patients with type 2 diabetes without retinopathy (NDR) and 62 healthy controls were recruited. The 16 and 32 Tds flicker electroretinography (ERG) was performed using a mydriasis-free, full-field flicker ERG recording device (RETeval). The vessel density (VD) of superficial capillary plexus (SCP) and deep capillary plexus (DCP), FD300 and ganglion cell complex (GCC) thickness in the macula were quantified using optical coherence tomography angiography (OCTA). The retinal nerve fibre layer (RNFL) thickness and the radial peripapillary capillary (RPC) density in the peripapillary area were also measured with OCTA. Results Parafoveal and perifoveal VD in both SCP and DCP decreased in NDR group in comparison to control group (all p<0.01). However, macular GCC thickness was comparable between the two groups (p=0.661). Peripapillary RNFL thickness and RPC density were significantly lower in NDR group (p<0.001 and p=0.009, respectively). With regard to ERG parameters, delayed implicit time and decreased amplitude were found in NDR group in comparison to the control group (all p<0.01). In the multiple linear regression analyses, delayed implicit time for 16 and 32 Tds stimuli was significantly correlated with increased HbA1c (β=0.350, p<0.001; β=0.328, p<0.001, respectively) and decreased VD of SCP in the parafoveal region (β=−0.266, p=0.013; β=−0.253, p=0.005, respectively). However, delayed implicit time for 16 and 32 Tds stimuli was not correlated with the thickness of GCC (β=−0.008, p=0.818) in multiple linear regression analyses. Conclusion Functional and structural impairments have already started in diabetic retina even in the absence of visible retinal lesions. Subtle microvascular abnormalities rather than ganglion cell loss might be associated with early functional changes in NDR patients. Poor control of blood glucose was associated with delayed implicit time of flicker ERG in preclinical diabetic retinopathy.

Background and objectives The association of diabetic retinopathy (DR) and diabetic macular oedema (DME) with renal function in southern Chinese patients with diabetes is poorly understood. So we aimed to study the correlation between stage of DR and DME with stage of estimated glomerular filtration rate (eGFR) and stage of urine albumin-to-creatinine ratio (UACR), and to explore the systemic risk factors for DR and DME. Design and setting This single-centre retrospective observational study was conducted from December 2017 to November 2018. Participants 413 southern Chinese patients with type 2 diabetes mellitus. Outcome measures The correlations between stage of DR and DME with stage of eGFR/UACR were assessed by Spearman’s or χ² analyses and represented with histograms. Risk factors associated with the occurrence of DR and DME were performed by logistic regression and represented with nomograms. Results Stage of DR had a positive correlation with stage of eGFR (r=0.264, p<0.001) and stage of UACR (r=0.542, p<0.001). With the stage of eGFR/UACR being more severe, the prevalence of DME became higher as well (both p<0.001). The risk factors for DR were DM duration (OR 1.072; 95% CI 1.032 to 1.114; p<0.001), stage of UACR (OR 2.001; 95% CI 1.567 to 2.555; p<0.001) and low-density lipoprotein (LDL) (OR 1.301; 95% CI 1.139 to 1.485; p<0.001), while risk factors for DME were stage of UACR (OR 2.308; 95% CI 1.815 to 2.934; p<0.001) and LDL (OR 1.460; 95% CI 1.123 to 1.875; p=0.008). Conclusions Among southern Chinese patients, stage of DR and DME were positively correlated with renal function, while stage of UACR performed a better relevance than stage of eGFR.