Vitamin D and Ocular Diseases: A Systematic Review

Abstract

The contributory roles of vitamin D in ocular and visual health have long been discussed, with numerous studies pointing to the adverse effects of vitamin D deficiency. In this paper, we provide a systematic review of recent findings on the association between vitamin D and different ocular diseases, including myopia, age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), dry eye syndrome (DES), thyroid eye disease (TED), uveitis, retinoblastoma (RB), cataract, and others, from epidemiological, clinical and basic studies, and briefly discuss vitamin D metabolism in the eye. We searched two research databases for articles examining the association between vitamin D deficiency and different ocular diseases. One hundred and sixty-two studies were found. There is evidence on the association between vitamin D and myopia, AMD, DR, and DES. Overall, 17 out of 27 studies reported an association between vitamin D and AMD, while 48 out of 54 studies reported that vitamin D was associated with DR, and 25 out of 27 studies reported an association between vitamin D and DES. However, the available evidence for the association with other ocular diseases, such as glaucoma, TED, and RB, remains limited.

Keywords: age-related macular degeneration; dry eye syndrome; glaucoma; myopia; ocular disease; retinoblastoma; thyroid eye disease; uveitis; vitamin D; vitamin D receptor.

Figure 1

Schematic illustration of vitamin D synthesis pathway. Moreover, 7-dehydrocholesterol in the epidermis layer of skin absorbs UV-B radiation and is converted to pre-vitamin D₃. Vitamin D₃, by either the isomerization of pre-vitamin D₃ in the epidermal basal layers or intestinal absorption from the diet, binds to vitamin D-binding protein (DBP) in the bloodstream, transported to the liver. Vitamin D₃ is hydroxylated by 25-hydroxylase or sterol 27-hydroxylase. The resultant calcidiol (25(OH)D₃) is 1α-hydroxylated in the kidney by 1α-hydroxylase, yielding biologically active vitamin D (1,25(OH)₂D₃).

Figure 2

Systematic review flow diagram.