Visual field loss and gain comparable at 5 years in open-angle glaucoma patients

Control of IOP may not only stabilize the visual field but also allow improvement.

Issue: September 25, 2014

Rates of visual field loss and gain are comparable 5 years after baseline treatment in patients with open-angle glaucoma, according to an evaluation of the Collaborative Initial Glaucoma Treatment Study.

Study authors compared visual field gains and losses in patients who underwent treatment for open-angle glaucoma with either trabeculectomy or topical medications. Although the study emphasized that rates of improvement and loss were comparable during early follow-up, upon continued follow-up after 5 years, visual field loss became more predominant.

“Our study provides evidence to support advising patients with newly diagnosed open-angle glaucoma that the visual field loss they now have will not only stabilize but may also improve with effective IOP-reducing treatment,” David C. Musch, PhD, MPH, told Ocular Surgery News. “This can serve to augment the positive counsel clinicians should convey to patients upon diagnosing open-angle glaucoma.”

Case series analysis

The prospective, comparative case series published in the American Journal of Ophthalmology included 607 patients with newly diagnosed open-angle glaucoma who were randomized to treatment with trabeculectomy or topical medications. IOP levels for all patients from baseline through an average of 7 years were recorded. Control of IOP helps predict visual field improvement, the study concluded.

“Patients who presented at diagnosis with more advanced visual field loss were more likely to show improvement in the amount of loss over time when they received initial surgical treatment vs. medical management,” Musch said.

Researchers evaluated the change from baseline to follow-up in the mean deviation from visual field testing. Clinically substantial improvement or loss was defined as change in mean deviation of 3 dB or more, although visual field testing results are subjective and influenced by patient attentiveness, fatigue and anxiety, as well as how the test is administered and who is administering the test.

Follow-up outcomes

At follow-up years 1, 3 and 5, visual field loss was seen in 6.6%, 10.9% and 14.5% of patients, respectively, compared with visual field improvement in 7.5%, 12.7% and 13.9% of patients, respectively.

“The long-held premise that visual field loss, once documented, cannot be reversed is challenged by our findings, but in reality what we found makes sense,” Musch said. “We know that glaucoma affects retinal ganglion cell function. In some newly diagnosed patients, the function of these cells is not yet irreversibly affected and can be restored upon removing the negative influence of high IOP.”

The authors found that 18.7% of visits during the first 5 years in patients with a maximum IOP of 13 mm Hg or less, 13.4% of visits in patients with maximum IOP of 14 mm Hg to 17 mm Hg, 10.6% of visits in patients with maximum IOP of 18 mm Hg to 21 mm Hg, and 8% of visits in patients with maximum IOP of 22 mm Hg or more showed gains in mean deviation.

“While a definition of ‘good IOP’ must be tailored to the individual patient, our findings support what clinicians have known — that the measures of better IOP control, such as a lower IOP, a lower minimum IOP and sustained lower levels of IOP over time, are indicative of benefit in preventing further visual field loss,” Musch said.

The likelihood of visual field gains was greater in patients with low maximum IOP values compared with those with higher maximum IOP values.

“While glaucoma is indeed a chronic disease that requires treatment and monitoring, clinicians should convey encouraging counsel to patients that with adherence to treatment recommendations, their visual function can be retained and in some cases improve long term,” Musch said. – by Nhu Te

Reference:

Musch D, et al. Am J Ophthalmol. 2014;doi:10.1016/j.ajo.2014.04.003.

For more information:

David C. Musch, PhD, MPH, can be reached at the University of Michigan, Kellogg Eye Center, 1000 Wall St., Ann Arbor, MI 48105; email: dmusch@med.umich.edu.

Disclosure: Musch is a data and safety monitoring board member for Ivantis and a consultant to Glaukos and InnFocus.