An Investigation into the Relationship between Vitamin D Deficiency and the Incidence of Glaucoma

Abstract

Glaucoma is a common cause of irreversible blindness, with multiple factors contributing to its pathogenesis, including genetics, vasculature, and metabolism. Vitamin D insufficiency has been increasingly proposed as a modifiable risk factor, owing to its neuroprotective, anti-inflammatory, and vascular properties. Nevertheless, studies on its link with glaucoma have been contradictory. The purpose of this study is to explore the association between serum vitamin D concentration and primary glaucoma in adults. This hospital-based case–control study comprised 300 participants, who were aged ≥40 years (150 glaucoma cases and 150 matched controls) in West Libya. Cases had been diagnosed with primary open-angle or primary angle-closure glaucoma according to standardised international criteria, and the controls had no clinical signs of glaucoma. Serum 25-hydroxyvitamin D levels were assayed by means of chemiluminescent immunoassay and stratified into deficiency (<20 ng/mL), insufficiency (20–29 ng/mL), and sufficiency (≥30 ng/mL). Demographic, clinical, lifestyle, and biochemical data were recorded. Unconditional logistic regression was used to calculate crude and adjusted odds ratios with adjustment for possible confounders. Vitamin D deficiency was much more common in patients with glaucoma as opposed to controls (55.3% vs. 32.0, p < 0.001). Cases had significantly lower levels of vitamin D in the serum as compared to the controls (19.6 ± 8.4 vs. 26.8 ± 9.7 ng/mL). The independent effects of vitamin D deficiency on glaucoma were observed to be still significant after multivariate adjustment (adjusted OR = 2.21, 95% CI: 1.31-3.74, p = 0.003). Vitamin D deficiency was independently associated to a high probability of primary glaucoma. This evidence confirms the assumption that poor vitamin D status can contribute to the pathogenesis of glaucoma and requires future research to establish causality and the possible benefits of supplementation.