I read somewhere that a deficiency of Thiamin might make myopia or short sightedness worse, i think it was talking about the eye retaining too much water and therefore changing the refraction of the lens. This morning i awoke with a feeling of very dry in my right eye which has not happened before so i am linking it to the 1500mg of thiamine i took yesterday. I felt like i slept pretty well throughout the night but still awoke feeling run down and exhausted although maybe a little better as i'm happy to write this post which, normally, i would feel too lathargic to bother. The thiamine is supposedly required in helping an enzyme convert sugar to ATP in the cell which creates energy or some such similar process.