Strong Correlation of Renal Function with Choroidal Thickness in Patients with Type 2 Diabetes: Retrospective Cross-Sectional Study

The purpose of this study was to analyze the correlation between renal function and subfoveal choroidal thickness (SFChT) in treatment-naive proliferative diabetic retinopathy (PDR) patients. This study included 85 eyes of 52 treatment-naive PDR patients who underwent kidney function testing and urinalysis and 42 eyes of 33 age-matched controls. Treatment-naive eyes with PDR were categorized into pachychoroid and leptochoroid groups based on the SFChT of the control group. Kidney function profiles were compared between pachychoroid and leptochoroid groups; the relationship between kidney function profile and SFChT was evaluated using regression analysis. Compared with the pachychoroid group, the leptochoroid group had significantly higher serum creatinine (p = 0.026), cystatin C (p = 0.004), and phosphorus (p < 0.001) levels and a lower estimated glomerular filtration rate (eGFR) (p < 0.001). Multivariate linear regression analyses showed that SFChT was positively correlated with eGFR (Cystatin C) (p = 0.007) and negatively correlated with serum phosphorus (p = 0.001). SFChT of patients with eGFR < 30 mL/min/1.73 m2 and serum phosphorus level ≥4.0 mg/dL was less than that of patients with higher eGFR and lower serum phosphorus level. The choroidal thickness of treatment-naive PDR patients is closely affected by renal function. Kidney function test should be considered if SFChT of patients with treatment-naive PDR is reduced.