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X. Luo, N. B. Patel, R. S. Harwerth, L. J. Frishman; Correlation Between Multifocal Electroretinogram (mfERG) Measures and Focal Retinal Ganglion Cell/Inner Plexiform Layer (RGC/IPL) Thickness in Macaques. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1075.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate relationhips between focal measures of inner retinal function and RGC/IPL thickness in the central retina.
Ketamine and xylazine (IM) were used to anesthetize rhesus-macaque monkeys for laser treatments and functional/structural examinations. Unilateral ocular hypertension (OHT) was induced in animal eyes by argon laser trabecular treatments. The assessment of inner retina, which started before the laser treatments, included functional tests using mfERG (slow-sequence and global-flash protocols), and structural analysis using Spectralis HRA+OCT (raster and 3.4-mm circular scans) with a semi-automated segmentation of the RGC/IPL complex. For the slow-sequence recordings, RGC function estimates were based on the high-frequency oscillatory potential (OPs, 110-224 Hz) root mean square (RMS) amplitudes, and multifocal photopic negative response (mfPhNR) amplitudes after OPs were excluded with a 50 Hz low-pass filter. For the global-flash recordings, RGC function estimates was based on the low-frequency component (LFC) RMS amplitudes, for which the optic nerve head component is a major contributor.
For the three rings of hexagons of the mfERG stimulus array that covered the central 20° (diameter) of the retina (foveal hexagon excluded), the r2 values determined by linear regression between focal functional measures of the inner retina and RGC/IPL thickness measures generally varied from 0.5 to 0.8 (highest for mfPhNR) before laser treatment (p<0.0001). The preliminary data from eyes with OHT revealed concurrent reductions in the amplitudes of the functional measures and the thinning of the RGC/IPL layer, which improved the r2 values from regression analysis by 0.2, on average.
The relation between focal functional measures of inner retinal activity and RGC/IPL thickness could be adequately predicted by a linear model in central 20° of the retina.
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