Association between renal function and retinal neurodegeneration in Chinese patients with type 2 diabetes mellitus

Background Chronic kidney disease (CKD) and diabetic retinopathy (DR) are two serious complications of diabetes. However, the association between retinal neurodegeneration in DR and renal function decline is still unclear. Our objective was to evaluate the association by measure estimated glomerular filtration rate (eGFR), macular ganglion cell-inner plexiform layer (GC-IPL), and ganglion cell complex (GCC) thickness in patients with type 2 diabetes mellitus (T2DM). Methods We analyzed the baseline data of the Guangzhou Diabetic Eye Study. T2DM patients from communities in Guangzhou were enrolled and all participants went through ophthalmic and general examinations. The thickness of the macular GC-IPL and GCC in their right eyes were measured by swept-source optical coherence tomography. CKD was defined as eGFR <60 mL/min/1.73 m2. Results One thousand three hundred and nine patients were included (mean age 64.4±7.6 years, 59.1% female), and fifty-eight (4.4%) of them had CKD. Average macular GC-IPL thickness was significantly thinner in CKD patients (96.5±9.1 µm) than non-CKD patients (101.3±9.2 µm) (P<0.01). Average macular GCC thickness was also significantly thinner in CKD patients (123.5±13.2 µm) than non-CKD patients (129.9±12.8 µm) (P<0.01). The significant thinning of macular GC-IPL and GCC thickness presented in every gird in the macula (all, P<0.05) except for central grid (P≥0.05). In the patients without DR, the eGFR was linearly correlated with the average macular GC-IPL thickness [β=0.07 (95% CI, 0.02-0.12), P<0.01] and GCC thickness [β=0.09 (95% CI, 0.03-0.16), P<0.01] after adjustment for age, sex, axial length, intraocular pressure (IOP) and combination of hypertension. However, no linear correlation was found between eGFR and macular GC-IPL or GCC thickness in DR patients. Conclusions Renal function decrease is associated with the thinning of the macular GC-IPL and GCC in T2DM patients, suggesting the potential value of ganglion cell lose to detect early function decline in the kidney in diabetic patients, especially in patients without DR.