Can vitamin D protect against age-related macular degeneration or slow its progression?

Dietary vitamin D plays an important role in maintaining proper vision. Age-related macular degeneration (AMD) is a complex eye disease with unknown pathogenesis. Studies on dietary supplementation and AMD occurrence and progression have produced conflicting results. In its advanced stage, AMD may be associated with apoptosis, pyroptosis or necroptosis of retinal cells. Vitamin D has been reported to play a role in modulating each of these programmed death pathways. Vitamin D is a modulator of the immune system and it acts synergistically with two members of the regulators of complement activation family H and I, whose specific variants are the most important genetic factors for AMD pathogenesis. Angiogenesis is an essential component of the neovascular form of AMD, the most devastating type of the disease and vitamin D is reputed to possess antiangiogenic properties. Cellular DNA damage response is weakened in AMD patients and so it is another process that can be modulated by vitamin D. Finally, impaired autophagy is claimed to play a role in AMD and emerging evidence suggests that vitamin D can influence autophagy. Therefore, several pathways of vitamin D metabolism and AMD pathogenesis overlap, suggesting that vitamin D could modulate the course of AMD.