Early Treatment to Prevent Glaucoma

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For decades doctors have been lowering the pressure within the eye with drugs or surgery to prevent blindness in people with glaucoma. Unfortunately, there was no evidence to prove these treatments actually work. Uncertainties surrounded the question of whether treatment even delayed the onset of vision loss. Some people with glaucoma progress to blindness despite having their intraocular pressure brought under control. And some people with normal pressure develop glaucoma.

In a recent commentary for the British Medical Journal, ophthalmologist R. Wormald, MD, described the ethical dilemma facing researchers, "Evidence was lacking that lowering pressure was effective, yet it was considered unethical to withhold treatment from a control group." Researchers found ways to circumvent the problem, according to Dr. Wormald, by being selective about the study participants. The definition of glaucoma involves not only high intraocular pressure but also optic nerve damage. Therefore, one option is to design a trial solely for people with normal-pressure glaucoma, a group that would not be treated anyway; another is a trial including people with ocular hypertension but no evidence of optic nerve damage. The latter research route produced the first clinical trial to show that the standard practice of prescribing topical glaucoma drugs is more effective than leaving people untreated. The 1,600 participants had elevated intraocular pressure and no optic nerve damage. All were at risk for developing primary open-angle glaucoma. They were randomly assigned to take topical anti-glaucoma medication or no treatment. After five years, 4.4% of those on the drug developed open-angle glaucoma, compared with 9.5% of those who did not take a drug.

Another newly published trial conducted in Sweden took on the question of whether reducing intraocular pressure in people with primary open-angle glaucoma prevents the disease from progressing. The 255 participants, aged 50 to 80 years and in the early stages of glaucoma, agreed to be randomly assigned to laser surgery plus topical medication, or no treatment. After six years, the disease progressed in 58 of the 129 treated people, compared with 78 of 126 untreated people. The most frequently prescribed anti-glaucoma drugs, used in this trial and sold under many brand names, are beta-blockers, or topical versions of anti-hypertension drugs. Two treated people in the Swedish study developed asthma, a known risk of this anti-glaucoma drugs; and the treated people had a higher rate of "nuclear cataracts," a newly identified risk thought to be due to the drug.

Though these two trials provide important new information, they did not last long enough to show whether treatment prevents blindness.

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