Pattern ERG useful for detecting early to moderate glaucoma

MIAMI — Retinal response measured with pattern electroretinogram may serve as a complementary diagnostic tool to detect early glaucoma, according to a physician speaking here.

Lori Ventura, MD, delivered a presentation on the new technology at Bascom Palmer Eye Institute's Inter-American Course in Clinical Ophthalmology.

Pattern electroretinogram (PERG) is a retinal response test that directly and objectively measures retinal ganglion cell function, Dr. Ventura said. Instead of using a flash of light, like a standard electroretinogram, PERG uses light and dark bars rapidly alternating at a frequency of 16 Hz to elicit a mass cell response, she said.

In studies, Dr. Ventura and colleagues at Bascom Palmer have shown that patients with apparently normal visual function may have abnormal structures that can be detected using PERG.

"The IOP threshold for damage to the retinal nerve fiber layer differs from patient to patient," Dr. Ventura said. "There is no way for us to know what the true pressure threshold is. The cutoff of 21 mm Hg was a myth for open angle glaucoma, and the targets we establish in our day-to-day practices are based on assumptions that our patients ... will match the profiles of studies done in the past," she said.

PERG technology has been available for several years, but it has never been widely applied because it requires electrodes to be placed directly on the surface of the eye, Dr. Ventura said. Vittorio Porciatti, DSc, also a faculty member at Bascom Palmer, modified the device so that the electrodes can be placed on the skin, and now the test takes only 3 minutes, she said.

"PERG is not designed to replace visual field tests or optical coherence tomography," she said. "All these tests provide complementary information to the clinician."