Correlation between renal function and peripapillary choroidal thickness in treatment naïve diabetic eyes using SS-OCT

Purpose: To investigate the association between the estimated glomerular filtration rate (eGFR) and peripapillary choroidal thickness (pCT) and retinal nerve fibre layer (pRNFL) thickness in diabetic patients by using swept-source optical coherence tomography (SS-OCT). Methods: Ocular treatment-naive patients with type 2 diabetes mellitus registered in the community health system in Guangzhou, China were recruited to participate in this prospective cross-sectional study. The eGFR was determined using the Xiangya formula, and the renal function was categorized into non-chronic kidney disease (non-CKD), mild CKD, and moderate to severe CKD (MS-CKD) according to the guidelines. The pCT and pRNFL thicknesses at 12 o9clock were obtained using a SS-OCT by a circular scan with a diameter of 3.4 mm centring on the optic nerve head, and the data from only one eye in each patient were used. Results: This study included 1,408 diabetic patients, with a mean age of 64.4±7.8 years. The average pCT decreased with renal function deterioration, with 126.0 μm ± 58.0 μm for non-CKD, 112.0 μm ± 51.2 μm for mild CKD and 71.0μm ± 22.9 μm for MS-CKD, respectively (P<0.001). The pCT was found to be significantly thinner in CKD patients in all quadrantes (P < 0.05 in all regions) with the exception of the inferior quadrant, and the average pCT was positively correlated with eGFR (β = 0.3, 95%CI = 0.0 to 0.6, p = 0.021) after making adjustments for other factors. The pRNFL thickness in the nasal quadrant was significantly reduced in patients with CKD, and pRNFL thickness was positively correlated with eGFR (β = 0.1, 95%CI = 0.0-0.2, p = 0.009) after adjusting for other factors. Conclusion: Impaired renal function was associated with a reduction of pCT and pRNFL thickness in patients with type 2 diabetes. The measurement of pCT and pRNFL may provide additional information for predicting renal impairment.