INTRODUCTION
Medical treatment of glaucoma began in the late 1800s with the use of eserine and pilocarpine. In the United States, glaucoma treatment is typically begun with topical medications. The short-term goal of medications is to lower intraocular pressure (IOP). The long-term goals are to prevent symptomatic visual loss while minimizing the side effects from the treatments.
DESCRIPTION AND PHYSIOLOGY
Unless there are extreme circumstances, such as an IOP higher than 40 mm Hg or an impending risk to central fixation, treatment is started using a so-called one-eyed therapeutic trial. Typically, one type of drop is started in only one eye with reexamination in 3 to 6 weeks to check for effectiveness. Effectiveness is determined by comparing the difference in IOP in the two eyes before therapy with the difference in IOP after initiating therapy. For example, if IOP is 30 mm Hg OD (oculus dexter; in the right eye) and 33 mm Hg OS (oculus sinister; in the left eye) before treatment, and, following treatment of the right eye, IOP is 20 mm Hg OD and 23 mm Hg OS, the drug is not having any effect. If the IOP after starting treatment is 25 mm Hg OD and 34 mm Hg OS, then the drug is having an effect.
It should be noted that the monocular trial when instituting medical therapy has been the topic of intensive studies over the past few years. Realini has reported that the monocular drug trial is of little clinical value in patients being treated with latanoprost. Bhorade and colleagues came to a similar conclusion in their study of prostaglandin analogues. Regardless, it is common practice to initiate medical therapy once glaucomatous optic neuropathy is diagnosed, and a firm understanding of the limited number of glaucoma therapeutics is necessary to choose the best therapy for each individual patient.
There are several different classes of medications. All medications work to lower IOP through varying pharmacologic mechanisms. IOP is determined by the balance between secretion and drainage of aqueous humor. All medications either decrease secretion or increase outflow. In the subsequent sections, the mechanism of action, common side effects, and contraindications for the different classes of medications are presented.
Table 21-1 lists the medications
within each class that are available in the United States as of 2010 to 2011.
The side effects and contraindications described in this chapter are not a complete listing. I recommend that all clinicians read the package insert before prescribing any medication. The figures show sample bottles of medications available in the United States.
