The distinction of corneal water in free and bound fractions

The corneal water is studied by NMR measurements. There are two fractions of water, one more strongly bound to relaxation centres of proteoglycanes and the other almost freely diffusible as liquid bulk water. A quantitative analysis shows that the bound fraction makes up a very small part (less than 1%) of the total water. So nearly all the water is available for the nutrition of the cornea by diffusion.