ABSTRACT
Any modern text on the design and evaluation of therapeutic products must place into unique perspective the nature of the eye and requirements of ophthalmic dosage forms. The eye, perhaps better than any other bodily organ, serves as a model structure for the evaluation of drug activity. In no other organ can a practitioner, without surgical or mechanical intervention, so well observe the activity of an administered drug. With such modern instrumentation as the biomicroscope (Fig. 1), the specular microscope (Fig. 2), the confocal microscope capable of viewing the singlelayered corneal endothelium, and various devices for measuring intraocular pressure, blood flow, and electroretinal response, the ophthalmologist can readily track changes in ocular structures from the cornea to the retina and monitor their function and physiology. In so doing, the ophthalmologist and diagnostic scientist often detect signs of ocular or systemic disease long before sight-threatening or certain general healththreatening disease states become intractable. With such specialized instrumentation, the practitioner can view the activity of the drug product on the entire eye or, for those products administered to the internal structure of the eye, the activity or effect of the drug product on a cell, a group of cells, or entire tissues.
