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      Next Generation PERG Method: Expanding the Response Dynamic Range and Capturing Response Adaptation

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          Abstract

          Purpose

          To compare a new method for steady-state pattern electroretinogram (PERGx) with a validated method (PERGLA) in normal controls and in patients with optic neuropathy.

          Methods

          PERGx and PERGLA were recorded in a mixed population ( n = 33, 66 eyes) of younger controls (C1; n = 10, age 38 ± 8.3 years), older controls (C2; n = 11, 57.9 ± 8.09 years), patients with early manifest glaucoma (G; n = 7, 65.7 ±11.6 years), and patients with nonarteritic ischemic optic neuropathy (N; n = 5, mean age 59.4 ± 8.6 years). The PERGx stimulus was a black-white horizontal grating generated on a 14 × 14 cm LED display (1.6 cycles/deg, 15.63 reversals/s, 98% contrast, 800 cd/m 2 mean luminance, 25° field). PERGx signal and noise were averaged over 1024 epochs (∼2 minutes) and Fourier analyzed to retrieve amplitude and phase. Partial averages (16 successive samples of 64 epochs each) were also analyzed to quantify progressive changes over recording time (adaptation).

          Results

          PERGLA and PERGx amplitudes and latencies were correlated (Amplitude R 2 = 0.59, Latency R 2 = 0.39, both P < 0.0001) and were similarly altered in disease. Compared to PERGLA, however, PERGx had shorter (16 ms) latency, higher (1.39×) amplitude, lower (0.37×) noise, and higher (4.2×) signal-to-noise ratio. PERGx displayed marked amplitude adaptation in C1 and C2 groups and no significant adaptation in G and N groups.

          Conclusions

          The PERGx high signal-to-noise ratio may allow meaningful recording in advanced stages of optic nerve disorders. In addition, it quantifies response adaptation, which may be selectively altered in glaucoma and optic neuropathy.

          Translational Relevance

          A new PERG method with increased dynamic range allows recording of retinal ganglion cell function in advanced stages of optic nerve disorders. It also quantifies the response decline during the test, an autoregulatory adaptation to metabolic challenge that decreases with age and presence of disease.

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          Most cited references 37

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          Pattern electroretinography (PERG) and an integrated approach to visual pathway diagnosis.

          The pattern electroretinogram (PERG) provides an objective measure of central retinal function, and has become an important element of the author's clinical visual electrophysiological practice. The PERG contains two main components, a positivity at approximately 50ms (P50) and a larger negativity at approximately 95ms (N95). The P50 component is affected by macular dysfunction with concomitant reduction in N95. The PERG therefore complements the Ganzfeld ERG in the assessment of patients with retinal disease. In contrast, the ganglion cell origins of the N95 component allow electrophysiological evaluation of ganglion cell function both in primary disease and in dysfunction secondary to optic nerve disease, where selective loss of N95 can be observed. Both macular dysfunction and optic nerve disease can give abnormalities in the visual evoked cortical potential (VEP), and the PERG thus facilitates more meaningful VEP interpretation. This review addresses the origins and recording of the PERG, and then draws on extensive clinical data from patients with genetically determined retinal and macular dystrophies, other retinal diseases and a variety of optic nerve disorders, to present an integrated approach to diagnosis.
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            Electroretinographic responses to alternating gratings before and after section of the optic nerve.

             A Fiorentini,  L Mafei (1981)
            Electroretinographic (ERG) responses to sinusoidal gratings reversed in contrast (pattern-reversal ERG) were recorded from both eyes of cats before and after unilateral section of the optic nerve. In the eye ipsilateral to the section, the pattern-reversal ERG remained unaltered for a few days after the section, the progressively decreased in amplitude, first at low and then at high spatial frequencies, to disappear completely about 4 months after the section, when ganglion cell degeneration was practically complete. The flash ERG remained unaltered. No alteration was observed in the contralateral eye.
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              Progressive loss of retinal ganglion cell function precedes structural loss by several years in glaucoma suspects.

              We determined the time lag between loss of retinal ganglion cell function and retinal nerve fiber layer (RNFL) thickness. Glaucoma suspects were followed for at least four years. Patients underwent pattern electroretinography (PERG), optical coherence tomography (OCT) of the RNFL, and standard automated perimetry testing at 6-month intervals. Comparisons were made between changes in all testing modalities. To compare PERG and OCT measurements on a normalized scale, we calculated the dynamic range of PERG amplitude and RNFL thickness. The time lag between function and structure was defined as the difference in time-to-criterion loss between PERG amplitude and RNFL thickness. For PERG (P 90%). Post hoc comparisons demonstrated highly significant differences between RNFL thicknesses of eyes in the stratum with most severely affected PERG (≤50%) and the two strata with least affected PERG (>70%). Estimates suggested that the PERG amplitude takes 1.9 to 2.5 years to lose 10% of its initial amplitude, whereas the RNFL thickness takes 9.9 to 10.4 years to lose 10% of its initial thickness. Thus, the time lag between PERG amplitude and RNFL thickness to lose 10% of their initial values is on the order of 8 years. In patients who are glaucoma suspects, PERG signal anticipates an equivalent loss of OCT signal by several years.
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                Author and article information

                Journal
                Transl Vis Sci Technol
                Transl Vis Sci Technol
                tvst
                tvst
                TVST
                Translational Vision Science & Technology
                The Association for Research in Vision and Ophthalmology
                2164-2591
                22 May 2017
                May 2017
                : 6
                : 3
                Affiliations
                [1 ]Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
                [2 ]Jorvec Corp., Miami, FL, USA
                [3 ]Department of Biomedical Engineering, University of Miami, Miami, FL, USA
                [4 ]Johns Hopkins Wilmer Eye Institute, Columbia, MD, USA
                [5 ]Intelligent Hearing Systems Corp., Miami, FL, USA
                Author notes
                Correspondence: Vittorio Porciatti, Bascom Palmer Eye Institute, McKnight Vision Research Center, University of Miami Miller School of Medicine, Miami, FL, USA. e-mail: vporciatti@ 123456med.miami.edu
                Article
                tvst-06-03-05 TVST-16-0455
                10.1167/tvst.6.3.5
                5444497
                Copyright 2017 The Authors

                This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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