MALIK Y. KAHOOK, LISA S. GAMELL, and JOEL S. SCHUMAN
After diagnosing a patient with glaucoma, in the United States the clinician usually prescribes topical medication as the initial treatment regimen. Ophthalmologists are fortunate to have many drugs in their arsenal today that are effective at lowering intraocular pressure (IOP) while requiring less frequent dosing and causing fewer systemic and ocular side effects than previous generations of glaucoma medications. While this provides the clinician with more options, it can also cause confusion. The ophthalmologist must choose one from among more than a handful of drops as initial single therapy. This decision is more clear-cut when patients have relative contraindications to particular drugs, such as avoiding beta blockers in patients with asthma or heart block or trying alternatives to carbonic anhydrase inhibitors (CAIs) in patients who are sulfa allergic. Otherwise, decisions may often be based upon experience or the clinician's comfort level with a particular medication.
More difficult decisions arise when disease progresses and a change in therapy is indicated. Options include adding additional medications, substituting one medication for another, or performing a surgical procedure, such as laser or filtration surgery. Which path the ophthalmologist follows depends not only upon clinical parameters such as disease severity but also upon patient parameters, including age, compliance, and quality-of-life issues. Preceding chapters provide pharmaco-logic information on the various classes of drugs: adrenergic agents, beta blockers, CAIs, cholinergics, osmotics, and prostaglandin analogs (PAs). The goal of this chapter is to guide the clinician in using these drugs to the patient's maximal benefit.
11.1 ADJUNCTIVE THERAPY: FIRST-LINE DRUGS
Which drug to use as initial single therapy depends on many factors, including the patient's health, allergies, and the amount of pressure reduction needed to reach target pressure. In the past (1980s, 1990s, and very early twenty-first century), beta blockers were the preferred first-line glaucoma drug because they were effective for lowering IOP and were relatively well tolerated when compared to other available medications. In addition, until the introduction in the United States of apraclonidine in 1989 and PAs in 1996, beta blockers and direct- and indirect-acting cholinergics were the most potent topical agents available. The current list of medications for glaucoma, including alpha agonists, CAIs, and PAs, provides multiple alternatives for initial therapy. Most ophthalmologists would agree that PAs, with once-daily dosing, excellent IOP-lowering effect, and few side effects, have replaced beta blockers as the most commonly used agent for first-line therapy.
Regardless of which drug is chosen as the first-line agent, the clinician should have a clear goal for IOP reduction in mind. The term target pressure is not the most accurate, since there is no magic number that will guarantee disease stability. A reasonable goal is approximately a 20-30% reduction in IOP;1 it is often useful to perform a monocular drug trial, where the drop is given in one eye alone to see if an adequate IOP-lowering effect is achieved.2 If an acceptable IOP reduction results, the drug may be added to the other eye. If the drug does not appear to be efficacious, an alternative drug may be tried. Bear in mind that a monocular trial provides the most information when the IOP is similar in both eyes. In addition, caution should be used if the IOP is very high in a patient with notable retinal nerve fiber layer or visual field damage. In such a patient, a monocular trial is not appropriate, and the clinician should attempt to quickly and effectively lower IOP in both eyes.
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