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John R Hetling, Shresta Patangay, Oksana Persidina; Simultaneous recording of local (sector) responses in peripheral pattern ERG (pPERG). Invest. Ophthalmol. Vis. Sci. 2019;60(9):2507.
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© ARVO (1962-2015); The Authors (2016-present)
Components of the pattern ERG (PERG) response reflect the function of retinal ganglion cells (RGC). A PERG stimulus was developed to probe RGC function in the peripheral retina (peripheral PERG, pPERG; Patangay et al., TVST 2018). The pPERG stimulus can be configured to probe sectors of the peripheral retina, useful for measuring local changes in function. The response from each sector is proportionally smaller in amplitude, requiring additional averaging to achieve acceptable signal to noise ratio; probing multiple sectors in series significantly extends the test time compared to using the full pPERG stimulus. Here we evaluate a technique for reducing the test time required to measure local RGC function by recording multiple sectoral responses simultaneously.
The pPERG stimulus is hemispherical, with 4 annular rows of 30 checks each. For each subject (n=4), the eye was positioned such that the inner and outer rows of checks appeared at 25 and 55 degrees (half angles) of eccentricity, respectively, and each check subtended approximately 5 degrees. The inner and outer rows defined two ring sectors; the middle two rows were turned off. Responses to each sector were recorded separately, at both 4.1 and 4.6 reversals per second (RPS). Then both sectors were turned on, each driven at a different reversal rate (4.1 or 4.6 RPS), and the response recorded to this mixed stimulus. The continuously recorded mixed response was parsed twice, using windows corresponding to the 4.1 and 4.6 RPS stimuli, and then each set of equal length windows was averaged.
Responses to the inner and outer ring sectors had very distinct waveforms (amplitudes and implicit times). For a given sector, the responses to 4.1 and 4.6 RPS stimuli were indistinguishable. When driving both sectors simultaneously but at different reversal rates, the appropriately parsed response (4.1 or 4.6 RPS) was indistinguishable from the response recorded from that sector when recorded separately.
Given the local or sectoral dysfunction and damage that characterizes glaucoma and other diseases, and the local rescue expected from certain therapies, measuring local responses is important for early diagnosis and monitoring. Here we describe a method of acquiring multiple local pPERG responses simultaneously, in the time previously required to acquire a single local (i.e. sector) response.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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