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Momoyo Menz, Michael Fendick, Erich Sutter; Electrophysiological Test for the Assessment of Dysfunction in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5128.
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To assess the glaucomatous optic nerve dysfunction using the multifocal ERG (mfERG) with an algorithm that provides a quantitative assessment of nerve fiber function, based on a ratio of an optic nerve component and a retinal component in the same eye. This is advantageous over the multifocal VEP (mfVEP) that requires a comparison to the fellow eye.
MfERG testing was performed on 10 normal subjects and 10 patients with asymmetrical glaucoma. One eye, "affected eye", of each patient had a well-established visual field defect mapped with full-threshold perimetry with a Humphrey Visual Field (HVF) instrument. The fellow eye, having no field defects, is labeled "unaffected". A special mfERG stimulation protocol (global flash paradigm) was used to enhance a contribution to the ERG originating from ganglion cell fibers at the optic nerve head (Optic Nerve Head Component, ONHC). A new algorithm now, available in VERIS 6.4, separates the ONHC from retinal response contribution and estimates its relative magnitude. At each stimulus location the ratio ONHC/Retinal response is used as an estimate of nerve conduction.
The mfERG demonstrated ONHC abnormalities in the "affected eye" of all 10 patients in support of the HVF results, sometimes exceeding the field defects seen with the HVF. Lesser abnormalities were also seen in some of the "unaffected" patient eyes.
Our results suggest that global flash mfERG stimulation combined with an algorithm for component separation can be used to objectively map loss in nerve fiber function. Unlike the mfVEP this test does not require a comparison to the fellow eye. Instead it uses the ratio of two response components from the same eye. It thus holds promise as a sensitive test in bilateral disease.
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