Design and evaluation of controlled release systems for the eye

The in vivo behavior of new ophthalmic preparations was evaluated by measuring pharmacodynamic effects such as the miotic response in man and rabbit. A gamma scintigraphy technique was used to measure the distribution of formulations over the ocular surface. New formulations such as a pH-sensitiue dispersion, a temperature setting gel and a natural mucopolysaccharide (hyaluronic acid) belonging to the class of glycosaminoglycans were extensively studied. The latter plays an essential role in tissue hydration and lubrication. This natural polymer, due to its capacity to retain water, seems to bind to cell membranes and can therefore be used as a suitable vehicle for controlled drug delivery to the eye.