Treating glaucoma: There's life after beta-blockers

Issue: February 1996

[videoangiogram] --- Detecting glaucoma: Videoangiogram of retinal circulation obtained with the scanning laser ophtalmoscope.

BALTIMORE—Beta-blockers remain a first-line treatment for adult open-angle glaucoma, but optometrists must choose another therapy if they lose effectiveness. Some glaucoma experts prefer apraclonidine (Iopidine, Alcon) if beta-blockers fail to achieve IOP targets; others opt for dorzolamide (Trusopt, Merck) in selected patients.

A new first-line therapy, latanoprost (Xalatan, Pharmacia-Upjohn), is also on the horizon. In December, a Food and Drug Administration advisory panel recommended its approval for first-line glaucoma therapy.

Start with an IOP target

According to Alan L. Robin, MD, a glaucoma researcher here, the primary goal in glaucoma therapy is to control IOP to "prevent patients' vision from deteriorating," he said. "That goal is either a 30% drop in pressure or an IOP under 16 mm Hg, depending on where they start."

Robin sets this goal after considering the potential benefits and risks for each patient. A young patient with a family history of blindness caused by primary open-angle glaucoma, he said, should be considered high risk, and treatment should be aggressive. Other high-risk patients include those with high pressure without disease or other syndromes, such as pigmentary dispersion syndrome; African-American patients; and patients with a disk or Drance hemorrhage.

Once patients reach the target IOP, Robin examines them "at different frequencies depending on how compliant I think they are with their medication, their degree of optic nerve function and the type of disease they have."

FDA approval of latanoprost could change the equation in as soon as a few months. Robin said, "When latanoprost becomes available, it will probably be my first-line therapy."

Apraclonidine vs. dorzolamide

When beta-blockers fail to meet the IOP goal, Robin adds either pilocarpine or Iopidine. Adding Iopidine can lower IOP an additional 20%, he said. He may also add Propine (dipivefrin HCl, Allergan), but he said, "If the patient's on a nonselective beta-blocker, there's really no additivity with Propine."

Jimmy D. Bartlett, OD, of the University of Alabama in Birmingham, has begun to use Trusopt—a topical carbonic anhydrase inhibitor (CAI)—as a drug of second choice. He said many patients develop an allergic reaction to Iopidine, and tachyphylaxis is a problem as well. He believes Trusopt offers good pressure-lowering effects "without all of the side effects" of systemic CAIs.

Robin believes Trusopt and Iopidine are both good drugs, but for second-line therapy he is concerned about Trusopt's long half-life in the eye's red blood cells: about 140 days. Also, while the allergic reaction to Iopidine is straightforward, patients taking Trusopt must be monitored for moodiness, depression and central nervous system problems even though only 5% are allergic to it. "There are advantages and disadvantages to both," Robin said. "For my personality and my way of treating people, I like to know what I'm dealing with."

Robin said that when his patients develop allergic reactions to Iopidine, he switches them to pilocarpine. He said Ocusert (Alza) is an underutilized delivery system for pilocarpine, and it often works in patients where pilocarpine drops do not.

With Ocusert, the pilocarpine is in a small wafer that is placed under the lid and lasts for up to six days. "This treatment is better for people who would not be able to tolerate the browache, miosis or accommodative spasm," he said. "It works in about 60% to 70% of people."

If pilocarpine does not work, Robin then turns to either Trusopt or argon laser trabeculoplasty (ALT).

Systemic CAI as last resort

If Trusopt is not effective, Robin usually offers his patients the choice of ALT or a systemic CAI. A systemic CAI may be appropriate for patients who have had multiple failed filters, said Robin, who prefers to avoid systemic CAIs if possible.

One ALT procedure may not help the patient reach the target IOP. "If ALT doesn't work initially, it's not worth repeating," he said. "But if the procedure works, and after three years the pressure again has risen from the target pressure, then it is worth repeating."