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G. J. McLellan, C. B. Y. Kim, K. Seo, G. W. Heyne, J. N. Ver Hoeve; Pattern ERG Deficits in a Feline Model of Primary Congenital Glaucoma. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5482.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate inner retinal function in an inherited feline model of primary congenital glaucoma (PCG).
Pattern ERGs (PERG) were recorded in 12 normal adult cats and in 10 adult cats with PCG. Animals were anesthetized with ketamine / xylazine and pupils dilated with 1% tropicamide. The pattern display subtended 33 deg at a viewing distance of 50cm. The stimulus was aligned on the area centralis by back projection of the fundus on the screen. Refraction was optimized with trial lenses. Pattern stimuli were high contrast black and white horizontal stripes (at 5 spatial frequencies from 0.026-0.41 cpd) reversing at a rate of 4/sec. Responses were averaged over 100 stimulus presentations for each of two trials. Amplitudes and latencies of the waveforms equivalent to the N35, P50 and N95 were calculated for each test condition and results for both eyes of each cat averaged. Statistical differences between groups were evaluated by two-tailed student’s t-test with Bonferroni correction.
Transient PERG waveforms in normal cats were similar in shape to primate PERGs. Feline PERGs were characterized by a small amplitude, initial negative N35-like component, followed by larger positive (P50-like) and a negative N95-like component. Mean latencies at 0.204 cpd for N35-, P50- and N95-like components were 18.5+/-3.5, 51+/- 4.2 and 111+/-14.8 ms, respectively. The amplitude of the N95-like component was significantly reduced in glaucomatous cats at all 5 spatial frequencies tested (6.9+/-3.5µV, 0.026 cpd) compared to normal cats (16.3+/-3.9µV; p<0.00125). At the lowest spatial frequencies tested, the amplitude of the P50-like component was also significantly reduced in glaucomatous cats (9.4+/-4.1 µV, 0.026 cpd) compared to normal cats (15.9+/-3.3µV; p<0.00125). The latencies of the N35-like and P50-like components of the PERG were significantly prolonged in glaucomatous cats(means at 0.204 cpd: 33.7+/-7 and 58.5+/-3.2 ms, respectively)
PERG deficits were identified in all of the adult PCG cats tested. Reduction in the N95-like component of the PERG in affected cats is consistent with inner retinal dysfunction, that is likely attributable to early onset of IOP elevation that characterizes feline PCG. Our data indicate that feline PCG represents a promising model for the study of early functional changes in glaucoma, and for longitudinal evaluation of neuroprotective treatment strategies.
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