ABSTRACT
Paul J. Missel, John C. Lang, Denise P. Rodeheaver, Rajni Jani,
Masood A. Chowhan, James Chastain, and Terry Dagnon Alcon Research, Ltd., Fort Worth, Texas, U.S.A.
INTRODUCTION
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, optical coherence tomography (OCT)
instrument (Fig. 1), confocal microscope capable of viewing the single-layered corneal
endothelium, and various devices for measuring intraocular pressure (IOP), 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 (1)
(Fig. 2). In so doing, the ophthalmologist and diagnostic scientist often detect signs of
ocular or systemic disease long before sight-threatening or certain general health-
threatening disease states become intractable. With such specialized instrumentation, the
practitioner can view the activity of the drug product on the entire eye or the activity or
effect on a cell, a group of cells, or entire tissues for products administered to the internal
structure of the eye.
