Baseline characteristics of the transient pattern electroretinogram in non-human primates: inter-ocular and inter-session variability

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This study assessed the inter-ocular and inter-session variability of the transient pattern electroretinogram (PERG) in a group of non-human primates. The transient PERG was measured both eyes of 29 non-human primates, and again after three months in 23 eyes of 23 of these animals. Signals were elicited using a contrast (90%, 75 cd m−2) reversing (5 reversals sec−1) checkerboard pattern (0·56 cpd). PERGs were also measured for stimuli of varied spatial frequency (n=8, 0·07–2·22 cpd), contrast (n=4, 20–100%), mean luminance (n=4, 4·7–75 cd m−2) and defocus (n=5, +1, +2, +3 diopters). The inter-eye and inter-session limits-of-agreement (LOA; 95%) were determined for each PERG parameter. Variability was also compared with previous studies using the coefficient-of-variability (COV). Pharmacological blockade of the inner retinal contributions to the PERG measured under these conditions was conducted in one animal using intravitreal injection of tetrodotoxin (∼6 μM) and N-methyl-d-aspartic acid (∼6 μM). The N95 component of the primate transient PERG showed spatial tuning, with a peak between 0·14 and 0·28 cpd. This spatial tuning was not as apparent for the P50 component. A linear relationship between P50 and N95 amplitude was found with contrast and mean luminance. Both components were attenuated with the introduction of +2 diopters or more of defocus. The inter-session COV for the P50 and N95 components were 23·8 and 19·2%, respectively, while the LOA were 58 and 46%, respectively. The N95:P50 ratio had smaller inter-session variability, was robust to changes in contrast, mean luminance and defocus, and was effective for characterization of inner-retinal dysfunction after pharmacologic block.

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