Dry Eyes Support Group
Dry eyes is an eye disease caused by decreased tear production or increased tear film evaporation. Symptoms include burning and a sandy-gritty eye irritation that gets worse as the day goes on. The symptoms are often caused by a loss of water from the tears that results in tears that are too "salty" or hypertonic.

Given how widespread D-deficiency really is, and how hard it is to overdose on D3, I don't think this is a big deal.