Glaucoma’s future prevalence higher than previously thought

CHARLESTON, S.C. — By 2020, nearly 80 million people worldwide will have some form of glaucoma, researchers estimate. Presenters here at this year’s American Glaucoma Society meeting emphasized early identification of the disease, effective treatment strategies and patient education about family risk.

Harry A. Quigley, MD, discussed the increase in the number of patients with glaucoma. In 2010, 60.5 million people worldwide will have glaucoma, and that number will increase to nearly 80 million by 2020, he said.

Dr. Quigley noted that these numbers are much higher than previously published estimates. “Most of the counts of how many people might have glaucoma were using those kinds of blindness prevalence surveys which are heavily weighted in favor of identifying cataracts, but not glaucoma,” he said, referring to an estimate he himself did 10 years ago, as well as others.

His new forecast was based on data only from studies in which the eye was specifically examined for visual acuity and visual field, Dr. Quigley said in an interview with Primary Care Optometry News sister publication, Ocular Surgery News.

The data were divided into those from different ethnic groups, including Chinese, African and those of European descent, he said.

Dr. Quigley said the biggest change in the number of people affected by glaucoma would be detectable in India. He noted that Africans are the most heavily affected by open-angle glaucoma, while angle-closure glaucoma disproportionately affects the Chinese population.

“Angle-closure is one-third as common as open-angle, but blinds almost as many people because it is a more aggressive disease,” Dr. Quigley said.

Overall, he said, glaucoma is the second leading cause of blindness worldwide, disproportionately affecting some populations.

As with cataracts and trachoma, “women are also disproportionately affected by glaucoma,” he said. “World blindness is a problem that women suffer from much more than men.”

Dr. Quigley added that, in the developed world, 50% of glaucoma cases are diagnosed correctly and the patient is properly educated on the disease. In the developing world, “95% of the people have no idea they have glaucoma,” he said.

“I knew my previous work was wrong because we didn’t have the [power] to do the study, so this is a much better estimate,” he said. “I’ll stick by this until we have more studies.”

OHTS results validated by similar study

Results of a landmark U.S. study of ocular hypertension treatment were validated by similar results in a European trial, according to one of the key researchers.

Michael A. Kass, MD, said results of the Ocular Hypertension Treatment Study (OHTS) were recently compared to those from the European Glaucoma Prevention Study Group (EGPS), and “interesting coincidences and divergences” were found.

“They were similar enough to compare, but different enough to be worth it,” Dr. Kass said.

Only eyes that were untreated were included in the comparison of the two studies, he said. The incidence of progression to primary open-angle glaucoma in untreated eyes in the OHTS was 12.6%, and the incidence in the EGPS placebo group was 11.7%, he said.

In addition, the hazard ratios were “remarkably similar” between the two studies, he said. Hazard ratios for risk factors including age, heart disease, IOP, cup-to-disc ratio and central corneal thickness were not significantly different between the two studies.

“If you look at the hazard ratios, the thing that strikes you is how extraordinarily similar they are,” Dr. Kass said. “If they were any more similar, I think people would have accused us of fudging this data, of having made it up. It is remarkably similar across the two studies.”

Dr. Kass said researchers will now pool data from the two studies to tighten confidence intervals. He said a joint analysis of the two studies is currently being planned for presentation at the American Academy of Ophthalmology meeting this fall.

Use existing patients to identify family members at risk

Using current glaucoma patients to target family members gives eye care practitioners quick access to a high-risk population in need of testing and possibly treatment, according to a poster.

Constance Nduaguba, MD, recommends clinicians use their existing patients as a means of identifying family members at high risk. “We’d be targeting a population of people for screening who are already at a higher risk than the general population,” she said.

Dr. Nduaguba obtained a list of family members from current patients, and solicited them for glaucoma testing. The group that was subsequently tested was small and well educated, which Dr. Nduaguba said might have skewed the results. However, nearly one-third of the well-educated 102 original patients in this study had not recommended their family members to be tested. About 20% of those surveyed – original patients and family members – were not aware that glaucoma runs in families.

“We always ask in our assessment if anyone in their family has glaucoma,” she said. Patients do not always realize that, if they have glaucoma, their relatives are at a higher risk and should be tested.

Dr. Nduaguba said reaching out to this high-risk population through their family members is a straightforward way to find potential glaucoma patients.

“It’s easy to approach these people,” she said. “It’s easy to get contact information from the patients you’re already seeing. We need to actively tell them their family members are at risk and need to be assessed because they have a 10-fold increase if they’re a blood relative compared with the general population.”

Fixed brimonidine/timolol is effective

A fixed combination of two leading glaucoma medications is as effective as the two prescribed together and more effective than either prescribed alone, said E.R. Craven, MD. He said that the fixed combination of brimonidine 0.2%/timolol 0.5% was more effective in his study than either brimonidine and timolol singularly or in combination.

“The brimonidine/timolol fixed combination twice a day is as effective as the concurrent use of brimonidine and timolol,” Dr. Craven said. “And it is significantly more effective than either of the monotherapies given alone.”

In addition, he said, half as many patients discontinued use of the fixed combination drug as the brimonidine as a result of ocular allergy.

A total of 385 patients on the fixed combination drug were compared with 382 patients on brimonidine monotherapy and 392 patients on timolol monotherapy. This group was followed for 12 months. A second trial compared 188 patients on the fixed combination to 183 patients on concomitant brimonidine and timolol.

Dr. Craven said the fixed combination was not only better than results with either medication solely or with concomitant dosing, the fixed combination was also better than brimonidine monotherapy treatment in both long-term safety and ocular allergy issues.

IOP discrepancies found post-LASIK in thick corneas

Patients with thick corneas who undergo LASIK have greater discrepancies in Goldmann tonometer measurements postoperatively than patients with thinner corneas, according to a presentation here.

In a poster, Nina A. Goyal, MD, compared preoperative and postoperative Goldmann applanation tonometry readings in patients undergoing refractive surgery for myopia. She found inconsistencies between the preop and postop readings, with lower IOPs postoperatively in the patients with thicker corneas.

“It was the people with the thick corneas … who had the biggest discrepancies,” Dr. Goyal said. “If you’re going to do LASIK on these patients, and they’re glaucoma suspects, and you’re getting pressures of 12 mm Hg, you might be lulled into thinking that the pressure is fine. But we found these are the people you probably want to watch,” she said. “It’s counterintuitive, and we don’t know why.”

Greater IOP fluctuation may mean higher risk

A greater fluctuation in IOP may be associated with a significantly higher rate of glaucoma progression. The Advanced Glaucoma Intervention Study found that greater IOP fluctuation as measured by standard deviation was associated with a higher likelihood of visual field progression. Paul Lee, MD, of Duke University Eye Center, and colleagues sought to replicate these findings in a clinical population receiving ordinary care.

According to the study abstract, 151 randomly selected patients from 12 eye care practices across the United States were followed for at least 5 years. Information on visual field progression, ocular medications and IOP were gathered for 302 eyes. Necessary data were available for 84 eyes of 55 patients. The mean age was 62.9 years. Visual field progression occurred among 19% of eyes.

Using the Cox proportional hazards model to evaluate the association between progression and IOP fluctuation, increasing IOP standard deviation was found to be associated with an increasing risk of progression. The researchers stated that with each unit increase in IOP standard deviation, a 3.2 times higher rate of glaucoma progression was seen.

Anecortave acetate can reduce IOP for months

The effects of anecortave acetate can last months and can help lower IOP by more than 30% when combined with other medications, according to a presentation.

Alan L. Robin, MD, said eyes with intravitreal triamcinolone acetonide-induced glaucoma are complicated to treat because of months-long elevated IOP levels. “Over the past few years we have seen an almost epidemic of the use of intravitreal and subtenon steroids for a variety of retinal diseases,” he said.

Dr. Robin said the side effect of this type of treatment is an acute and long-lasting IOP rise. However in spite of maximum therapy, the patients he studied were still in need of surgery to lower IOP levels.

Dr. Robin injected anecortave acetate through an anterior juxtascleral depot in six patients whose mean IOP was nearly 40 mm Hg. In this patient group, Dr. Robin found more than a 10-mm Hg decrease in IOP. The drug itself, Dr. Robin said, stayed in the eye for about 3 months, and the effect lasted for as long as 10 months.

“All of these patients were surgical candidates,” he said. “We really showed that in six of seven, pressure lowered and three of six avoided surgery … It may have potential for other indications.”

Alcon will market the drug as Retaane in the United States when it receives regulatory approval. Retaane was submitted for U.S. and European approvals in 2004; however, Alcon recently withdrew its European application. Alcon is seeking approval of the drug as a treatment for patients with subfoveal choroidal neovascularization due to age-related macular degeneration.

Phaco-ECP combination effective

Combining cataract surgery with an endoscopic glaucoma treatment may be beneficial for patients with both cataract and moderate glaucoma, according to Stanley J. Berke, MD, FACS. Dr. Berke reviewed the results of a large, long-term study of phacoemulsification combined with endoscopic cyclophotocoagulation (ECP). The technique, which he has been performing for 6 years, is most suitable for patients with well-controlled glaucoma who need cataract surgery, he said.

“If they’re already having cataract surgery and they have glaucoma, I am immediately considering ECP,” Dr. Berke said in an interview with Ocular Surgery News. He also considers other factors such as how many medications the patient is taking, his or her tolerance for the medications, the status of the glaucoma and whether it is controlled.

Eyes that have well controlled, moderate glaucoma make the best candidates for phaco-ECP, Dr. Berke said.

He presented data on 707 eyes – 626 in the phaco-ECP group and 81 in a phaco-only control group – that were followed for up to 5 years. The phaco-ECP group had significantly lower mean IOP than the phaco-only group, Dr. Berke said.

The phaco-only group experienced an initial lowering of IOP, but levels “drifted back to where they were” by the end of 3 years of follow-up, he said.

“ECP is not a competing technology. It’s just an additional technology,” Dr. Berke said. “It’s better than doing nothing, but not as drastic as doing a trabeculectomy. … It’s nice to have something in the interim.”

This article also appeared in Ocular Surgery News, another SLACK Inc. publication.