Products to be instilled into the eye, while not parenteral by definition, have many similar and often identical characteristics. The formulation of stable, therapeutically active ophthalmic preparations requires high purity of ingredients as well as freedom from chemical, physical (particles), and microbial contaminants. These preparations usually require buffers to stabilize the pH of the product, additives to render it isotonic or nearly so, and stabilizers such as antioxidants for the particular ingredients.
Those ophthalmics used in larger quantities, such as eye irrigants, or in the case of devices such as contact lenses, are usually relatively uncomplicated solutions similar to large volume parenteral. One characteristic critical for ophthalmics is their freedom from pyrogens since pyrogens are not absorbed systemically from the eye: however, insofar as pyrogens are indicative of a microbiologically clean process, they should not be present.
Keywords: Ophthalmic, Eye drops, Eye emulsion, Contact lenses, Ocuserts