Vitamin D and Glaucoma: A Critical Review of the Literature

Figure 1

Normal vitamin D metabolism. Vitamin D can either be produced in the skin from 7-dehydrocholesterol under the influence of UV light, so-called vitamin D3 (cholecalciferol), or from ergosterol or directly absorbed from the diet as vitamin D3 and vitamin D2 (ergocalciferol). Either form is then hydroxylated to 25-hydroxycholecalciferol (calcidiol or calcifediol, 25(OH)D) in the liver by the cytochrome P450 (CYP) 27A1. It is then transformed mainly in the kidney by 25-hydroxyvitamin D3-1α-hydroxylase (CYP27B1) into 1α,25-dihydroxyvitamin D (1,25(OH)₂D or calcitriol).