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In-office pattern electroretinogram efficient for glaucoma diagnosis
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In-office electrophysiology with pattern electroretinogram technology is an effective, less invasive and time-efficient tool to diagnose glaucoma in patients with mild to moderate forms of the disease, according to one glaucoma specialist.
An in-office electrophysiology procedures takes about 20 minutes to complete, compared with the procedure in the clinical setting, which takes nearly an hour, Brian A. Francis, MD, told Ocular Surgery News.
“Traditionally, in terms of real clinical practice, even in academic centers, there is limited accessibility for glaucoma patients to get PERG, or electrophysiology, in general just because it is a more time-consuming exam. You have to have specialized equipment and a dedicated, trained person to do the testing,” Francis said.
However, the in-office technology scales down the equipment for easier access, and placement of the electrodes is less invasive for patients, he said.
Detecting dysfunction
Electrophysiology can potentially detect dysfunction in the retinal ganglion cells before structural loss or atrophy, which can be a sign of early glaucoma, Francis said.
The technology uses a pattern reversal stimulus with a fast temporally modulated stimulus of greater than 10 per second. This establishes a steady-state PERG instead of a transient wave pattern, Francis said.
“What the technology does is measure the steady-state response to the reversal stimulus,” he said. “It measures not only the magnitude of the waveform response but also the phase. So you could have someone with early disease who has a good magnitude response, but because there is some dysfunction, the repeat responses are out of phase, so there is a bit of a lag time. That is called ‘magnitude D,’ or ‘mag D.’ The mag D to mag ratio is the number we use clinically.”
Early detection
PERG can identify and detect glaucoma in many cases before it can be detected using OCT or visual fields, Francis said.
The technology also offers potential treatment endpoints for patients, he said.
“Because it can detect disease very early, there is a potential for reversal of the abnormality on PERG,” Francis said, citing a case example in which a patient with ocular hypertension showed abnormal PERG, and after IOP lowering with selective laser trabeculoplasty, the dysfunction was reversed.
“There is a potential for a treatment endpoint instead of just IOP where you can measure a functional endpoint change in these patients. That’s an exciting new area of data and research,” he said.
Future of PERG
The future of PERG and in-office electrophysiology will be improved, and uses will likely be expanded for glaucoma diagnosis, Francis said.
“Just like any other technology, like OCT, the technology will improve so that repeatability is better, variability is reduced, and tests will be increasingly more accurate,” he said. – by Robert Linnehan
- For more information:
- Brian A. Francis, MD, can be reached at Doheny Eye Institute, UCLA Department of Ophthalmology, Los Angeles, CA 90033; email: bfrancis@doheny.org.
Disclosure: Francis reports he is a consultant for Diopsys.