AS ANYONE who has examined a dirty eyedropper bottle retrieved from deep within a patient's pocket or purse knows, the preservatives added to the formulation of antiglaucoma medications play a crucial role in preventing ocular infection among patients receiving long-term therapy. The preservatives must have sufficiently broad spectrum to prevent the growth of bacteria, fungi, and other pathogenic organisms in multidose bottles opened and stored under less than ideal conditions. In many cases, the preservative must remain potent for many months.