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Glenwood G. Gum, Pamela P. Ko, Robert Sun, Valerie K. Ackley, Ricardo A. de Carvalho; The Effect of Monochromatic Filter Combinations for Optimizing the Photopic Negative Response in Normal Dichromatic New Zealand White Rabbits. Invest. Ophthalmol. Vis. Sci. 2011;52(14):701.
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© ARVO (1962-2015); The Authors (2016-present)
To develop an optimal procedure for a full-field electroretinogram(ERG) using the most appropriate background and stimulus filter combination in obtaining the photopic negative response (PhNR) in normal New Zealand White rabbits.
Six New Zealand White rabbits were used in this study, ages were between 15 weeks to 6 months, weighing at least 2.5 Kg at the time of the experiment. All rabbits were scotopically adapted for 60 minutes prior to the ERG procedures. ERGs were recorded with a 20 msec stimulus of photopic luminance. Initially the experiments determined the optimal background, in which the ERGs were recorded using white, green or blue background. After selecting the optimal background setting, the next experiments determined the most appropriate monochromatic filter and stimuli combination, where animals were light adapted for 10 minutes under a fixed background and paired with different filters at different stimuli (range -8 dB to +7.5 dB). Experiments were done in triplicate at three different time points. Statistical analysis was performed to determine the most sensitive and reproducible PhNR. An ANOVA and Tukey's multiple comparsion procedures were used for statistical analysis.
The blue background with green filter combination produced the most consistent, reliable and optimal PhNR amplitude for dichromatic rabbits. Optimal PhNR amplitudes were recorded at a stimulus setting of -2 dB with a range of 35 - 40 µV. The PhNR amplitudes decreased as the stimulus intensity increased from -2 dB to + 7.5 dB using the blue background with green filter combination. The yellow filter with blue background combination produced consistent result with smaller PhNR when compared to the green filter with blue background. The blue background with red filter which is used typically in other animal models or trichromatic retinal animals produced smaller PhNR with inconsisitent amplitudes. The blue or green background with white stimulus produced no recordable PhNR.
Based on the result of study, the most appropriate monochromatic filter for evaluating PhNR in the dichromatic rabbits is the blue background and green filter combination. Optimal PhNR amplitude is achieved at -2 dB stimulus intensity in the New Zealand White rabbit. The blue-, green- color coded retinal ganglion cells and the rods to cones ratio of 15:1of the dichromatic rabbit appears to provide the physiological bases of these results.
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