Vitamin D supplementation in diabetic retinopathy: an optical coherence tomography angiography study of changes in macular perfusion

Observational studies suggested a link between vitamin D deficiency (VDD) and diabetic retinopathy (DR). However, evidence from interventional studies on possible effects of VDD correction on retinal microvasculature in DR is scarce. This single-arm exploratory interventional study included 60 eyes from 30 patients with VDD and type 2 diabetes mellitus (DM), without DR or with mild or moderate non-proliferative DR (NPDR). Participants received oral vitamin D3 (50,000 IU/week for 8 weeks) followed by a daily maintenance dose (800 IU). Optical coherence tomography angiography (OCTA) imaging was performed before and three months after vitamin D repletion. Outcome measures were macular perfusion parameters and best-corrected visual acuity (BCVA). Linear mixed effects models were used to evaluate the association between changes in outcome measures with change in serum 25(OH)D3 levels. The mean serum 25(OH)D3 level increased significantly post-intervention (14.20 ± 4.04 to 55.82 ± 6.79 ng/mL; p < 0.001), and VDD was corrected in all patients. A small improvement was noted in BCVA with marginal statistical significance (0.12 ± 0.13 to 0.10 ± 0.13 Logarithm of the Minimum Angle of Resolution; p = 0.051). Other than a small reduction in parafoveal superficial vessel density at the superior quadrant (-3.23 ± 6.66%, p = 0.011), none of the perfusion metrics had changed three months after VDD correction. Linear models yielded no association between changes in serum 25(OH)D3 levels and alterations in BCVA or OCTA macular perfusion metrics. Based on this non-controlled interventional study, short-term effects of VDD correction in people with DM without severe DR does not appear to significantly influence the visual acuity or macular perfusion profile on OCTA.