Vitamin A is a family of fat-soluble vitamins. Retinal is one of the most active, or usable, forms of vitamin A. It plays an important role in vision, bone growth, reproduction, cell division and differentiation. It maintains the surface linings of eye and respiratory, urinary, and intestinal tracts. Vitamin A may help lymphocytes a type of white blood cell that fights infections, function more effectively. It also may help prevent bacteria and viruses from entering body by maintaining the integrity of skin and mucous membranes.