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Suresh Viswanathan, Laura J. Frishman, John G. Robson; The Uniform Field and Pattern ERG in Macaques with Experimental Glaucoma: Removal of Spiking Activity. Invest. Ophthalmol. Vis. Sci. 2000;41(9):2797-2810.
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© 2016 Association for Research in Vision and Ophthalmology.
purpose. To determine whether the uniform field and pattern ERGs that are
reduced in macaque eyes with experimental glaucoma have the same
methods. ERGs were recorded from 14 anesthetized adult macaques using DTL
electrodes. Six monkeys had laser-induced experimental glaucoma, and
two others received intravitreal injections of tetrodotoxin (TTX, 6μ
M) to block spiking activity of inner-retinal neurons. The remaining
6 animals were normal. Uniform fields and grating patterns (0.1–3 cpd)
were square-wave modulated at 1.7 Hz (transient) and 8 Hz (steady
state). The test field (42° × 32°) had a mean luminance of 44
cd/m2 and a contrast of 10% to 82%.
results. In normal eyes transient ERGs to uniform fields contained photopic
negative responses (PhNR) after the b-wave and after the d-wave. Transient pattern electroretinograms (PERGs) at
each contrast reversal showed positive (P50) potentials
followed by negative (N95) potentials of time course
similar to that of the PhNR. The PhNR and N95 were greatly
reduced or eliminated by experimental glaucoma and by TTX. Summing
responses to luminance increments and decrements of the uniform field
could simulate the PERG to low spatial frequency stimuli. Further, the
PERG responses to high spatial frequencies were similar to the
simulation in shape but slightly delayed in time. Experimental glaucoma
and TTX had similar effects on the N95 of the simulated
PERG as to those on the actual PERG. However, P50 was more
reduced by experimental glaucoma than by TTX, indicating a nonspiking
contribution to P50. For the steady state condition, the
uniform field ERG, the simulated PERG, and the actual PERG all were
affected by experimental glaucoma and TTX, indicating that they
contained contributions from the spiking activity of ganglion cells.
conclusions. The changes in the uniform field and PERG responses produced by
experimental glaucoma are related and are largely a consequence of
reduced spiking activity of ganglion cells and their axons. These
findings raise the possibility that the uniform field ERG could serve
as a useful alternative to the PERG in the assessment of clinical
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