Diabetic macular edema (DME) remains a leading cause of vision impairment in individuals with type 2 diabetes mellitus (T2DM). A retrospective case-control study published in Diabetes, Metabolic Syndrome and Obesity evaluated whether serum vitamin D3 levels were associated with DME after accounting for demographic, metabolic, and clinical factors.

The study included patients with T2DM attending a tertiary ophthalmology clinic. Cases had clinically and optical coherence tomography–confirmed DME, while controls had no DME. Patients with severe nonproliferative diabetic retinopathy (NPDR) or higher stage were excluded. Variables collected included age, sex, diabetes duration, glycated hemoglobin (HbA1c), body mass index (BMI), smoking status, vitamin D3 levels, comorbidities, and vitamin D supplementation. Vitamin D3 levels were categorized as <10 ng/mL, 10–30 ng/mL, and >30 ng/mL. Logistic regression identified independent predictors of DME.

Among 332 participants, 148 had DME and 184 served as controls. Individuals with DME had longer diabetes duration (17.21 vs 12.91 years; P<0.001) and lower mean vitamin D3 levels (16.71 vs 25.16 ng/mL; P<0.001). Vitamin D3 deficiency (<10 ng/mL) was independently associated with increased odds of DME, whereas vitamin D3 sufficiency (>30 ng/mL) was associated with lower odds. Cigarette smoking was associated with lower odds of DME.

These findings indicate an association between vitamin D3 deficiency and DME in this cohort. Interpretation should remain cautious due to potential selection bias, unmeasured confounding, and lack of adjustment for diabetic retinopathy severity. Further research is needed to clarify the relationship and the role of supplementation.