This chapter focuses on specific pharmacodynamic, pharmacokinetic, and drug delivery issues relevant to ocular therapy and imparted by the unique anatomy and function of this sensory organ, introduced at the outset of this chapter. Many of the pharmacological agents discussed here have been discussed in earlier chapters. Autonomic agents have several uses in ophthalmology, including diagnostic evaluation of anisocoria and myasthenia gravis, as adjunctive therapy in laser and incisional surgeries, and in the treatment of glaucoma | is surgical iridectomy, either by laser or by incision, but short-term medical management may be necessary to reduce the acute intraocular pressure elevation and to clear the cornea prior to laser surgery. As mentioned in other chapters, acute angle-closure glaucoma may be induced rarely in anatomically predisposed eyes by anticholinergic, sympathomimetic, and antihistaminic agents. Interestingly, however, individuals with those susceptible angles do not know they have them. As far as they know, they do not have glaucoma and are not aware of a risk of angle-closure glaucoma. Yet, drug warning labels do not always specify the type of glaucoma for which this rare risk exists. Thus, unwarranted concern is raised among patients who have open-angle glaucoma, by far the most common form of glaucoma in the United States, and who need not be concerned about taking these drugs. In any event, in anatomically susceptible eyes, anticholinergic, sympathomimetic, and antihistaminic drugs can lead to partial dilation of the pupil and a change in the vectors of force between the iris and the lens. The aqueous humor then is prevented from passing through the pupil from the posterior chamber to the anterior chamber. The result can be an increase in pressure in the posterior chamber, causing the iris base to be pushed against the angle wall, thereby closing the filtration angle and markedly elevating the intraocular pressure.
