Allergan Education Forum
Pursuing Early Glaucoma Detection
New research and technologies are improving how physicians diagnose and track the disease.
ANNE L. COLEMAN, M.D., PH.D. * LEON W. HERNDON, M.D. * JOEL S. SCHUMAN, M.D.
Recent research has underscored the value of regular optic nerve evaluation and illustration. However, the latest studies of conformance with preferred practice patterns in glaucoma indicate that this approach isn't yet universal. One study that looked at chart reviews found that only 53% of patients had an optic nerve photograph or drawing at their initial evaluation.
"For half of patients, physicians don't examine and document the optic nerve, yet research has shown we can detect glaucoma by this means far sooner than we'll notice resulting visual field loss," says Anne L. Coleman, M.D., Ph.D., professor of ophthalmology at the Jules Stein Eye Institute, University of California Los Angeles School of Medicine.
"In fact, studies show some people who go blind from glaucoma had no visual field loss 10 or 20 years earlier," says Dr. Coleman. "We need to look at the optic nerve regularly to document any changes."
|ANNE L. COLEMAN, M.D., Ph.D. LOS ANGELES||LEON W. HERNDON, M.D. DURHAM, N.C.||JOEL S. SCHUMAN, M.D. PITTSBURGH|
Leon W. Herndon, M.D., associate professor of ophthalmology at Duke University Eye Center, Durham, N.C., also sees a gap between best practice and the learning curve among physicians and other eyecare professionals.
"When we consider the current evidence, it's clear that primary open-angle glaucoma is undertreated, particularly patients with normal-tension glaucoma," says Dr. Herndon. "I'm often asked to comment on patients whose glaucoma was missed by a pressure check. Doctors haven't looked at the optic nerve soon enough to realize that glaucoma was present."
Dr. Herndon explains how the Ocular Hypertension Treatment Study (OHTS) found important differences in functional changes (visual field) versus structural changes (the optic nerve) in glaucoma patients. Patients may exhibit defects in their visual field at one visit, and then have different results in later tests. In contrast to this fluctuation, closely following retinal nerve fiber layer (RNFL) imaging studies can help physicians more accurately diagnose glaucoma and follow its progression.
"Tracking optic nerve changes, in tandem with a higher index of suspicion for detecting glaucoma will help us detect the disease earlier and respond to its progression."
--Leon W. Herndon, M.D.
What to look for
As physicians concentrate more closely on optic nerve evaluation, they're becoming more adept at recognizing subtle glaucomataous optic nerve changes.
"Focus on more than just the cup-to-disc ratio," advises Joel S. Schuman, M.D., director of the University of Pittsburgh School of Medicine Eye Center. He suggests checking neural rim integrity for thinning and notching and assessing any loss in the RNFL. Physicians also should look at the contour, cupping and curvature of the optic nerve, says Dr. Schuman, as well as hemorrhage on the disc margin, which suggests damage.
"Rim thickness typically follows the ISNT rule -- inferior thickest, to superior, to nasal, to temporal thinnest," says Dr. Schuman, "and we need to be suspicious if it doesn't."
Of course, RNFL changes can be tracked over time only with appropriate documentation. "Physicians need to document patients' optic nerve through observations, photos and drawings to establish a baseline for future analysis," says Dr. Schuman.
Dr. Herndon agrees, "Tracking optic nerve changes, in tandem with a higher index of suspicion for detecting glaucoma will help us detect the disease earlier and respond to its progression."
New technology is an important aspect of making optic nerve evaluation a routine part of glaucoma diagnosis and management. "It's essential for physicians to pursue early glaucoma detection by routinely examining the optic nerve, and imaging technology can be a big help," says Dr. Schuman. "Several studies have shown that imaging devices perform at least as well as the expert observer, so they offer an excellent opportunity to examine the optic nerve at an expert level and standardize the assessment."
According to Dr. Schuman, one advantage of imaging devices is they provide an objective, quantitative assessment of the RNFL and the optic nerve. The images are revealing and the devices' software can offer data analysis and trending.
Advanced perimetry technologies also can aid diagnosis. According to Dr. Coleman, "If you see cupping of the optic nerve but no visual field problem, you can try a selective functional test. Short-wavelength automated perimetry or frequency-doubling perimetry can detect visual field loss 3 to 5 years before standard perimetry."
After diagnosis: Lowering IOP
While physicians who are evaluating the optic nerve are achieving earlier, more accurate diagnoses, they're also improving their ability to preserve vision. Studies such as the Advanced Glaucoma Intervention Study, the OHTS and the Early Manifest Glaucoma Trial have shown the importance of lowering IOP even a small amount, and this knowledge has applications for target pressures.
"There is ample weight in the literature to support telling our patients that lowering IOP even 1 mm Hg may limit their visual field loss over time," Dr. Herndon explains. "Our goal now is to establish target pressures according to the evidence in these studies."
Earlier diagnosis leads to earlier treatment, says Dr. Herndon. In the past, physicians didn't treat patients with preperimetric glaucoma. By acknowledging that optic nerve changes are often the first signs of glaucoma and that these changes affect patients' real-life vision, physicians are creating an opportunity to establish early IOP control.
More focus for the future
By carefully evaluating the optic nerve and integrating imaging technology, physicians now can diagnose glaucoma earlier, giving them the opportunity to halt or slow disease progression.
"It's important to pay attention to quality-of-life issues, as well," says Dr. Coleman. "We're finding that the severity of visual field loss correlates with a patient's perceived visual disability. This causes trouble with daily tasks, which can increase the risk of falls, fractures, loss of independence and social isolation."
Quality of life is yet another reason for earlier intervention in glaucoma.