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Clinicians have an array of techniques and devices available to them for assessing progression of glaucoma, and more are under development. Such tools rely on either subjective or objective measurements, with the latter generally providing more reliable results. Frequent, long-term follow-up with one or more of those approaches will increase the likelihood of detecting progression early.
New Orleans-The recognition of glaucomatous progression is the principal goal of patient management and can be accomplished with an assortment of tools, with more in the development stage that have the potential to enhance clinicians' detection skills.
The essential elements of monitoring progression include an optic nerve head evaluation at every patient visit as well as photography of the optic nerve and, if available, imaging every 6 to 12 months, according to Joel S. Schuman, MD, FACS, who described techniques for detection of progression in a presentation here at the annual meeting of the American Academy of Ophthalmology.
Other steps to detect progression include annual visual field testing in stable patients and more frequent testing in those who have a high risk of progression. Structure-function correlation with imaging, if possible, also can be helpful in taking care of patients, said Dr. Schuman, the Eye and Ear Foundation professor and chairman of ophthalmology, UPMC Eye Center, Eye & Ear Institute, University of Pittsburgh Medical Center.
Tools for objective, quantitative evaluation of the optic nerve and RNFL also have been developed. Those devices are roughly equivalent in their ability to distinguish a glaucomatous eye from a healthy one. However, longitudinal evaluation with those devices is a less mature field, according to Dr. Schuman, who briefly described several current technologies.
Confocal scanning laser ophthalmoscope assessment of the optic nerve at baseline has been shown to be a strong predictor of subsequent visual field loss that might not occur for many years. A a confocal laser scanning microscope (Heidelberg Retina Tomograph, Heidelberg Engineering) is a good choice for assessing the topography of the optic nerve. Recently upgraded software has greater sensitivity and specificity that should result in a better grasp of the degree of progression, Dr. Schuman said.
Scanning laser polarimetry is a technology used for RNFL assessment; software for assessing progression with this device is in clinical trials and not yet commercially available. It evaluates progression by both trend and event analysis, for example by marking differences in RNFL thickness between exams or displaying areas of change on an RNFL thickness map. It also can provide predictions and data on trends over time.
Optical coherence tomography (OCT), which Dr. Schuman helped develop, is one of the most powerful tools for glaucoma management available to clinicians. It has been evaluated for longitudinal assessment of patients. A recent paper showed that more progression events were detected with OCT than with visual field exams in a group of glaucoma patients followed over time.
"That does not mean that all of the patients who were detected by OCT actually had disease that was getting worse," he continued. "That doesn't say anything about specificity, but the sensitivity was higher. On the other hand the converse is true as well, since we really don't have any good gold standards for assessing progression."
In another study, the authors analyzed baseline RNFL thickness measurements taken with OCT and looked for subsequent development of glaucomatous visual field loss. They concluded that OCT was a predictor of future visual field loss, Dr. Schuman said. Technology for progression assessment with OCT is not commercially available, although clinical studies are underway.
"One of the benefits of imaging technologies is that they standardize the interpretation of the ocular structure at the expert level," Dr. Schuman said, explaining that they enable less experienced clinicians to interpret the objective signs of progression as well as their more adept peers.
"These technologies should be used as a method to drive us back to the patient when they identify areas that may be abnormal, and have us take a second look if we didn't see that area before," Dr. Schuman continued. "We should be looking for structure-function correspondence."