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F.M. Moreno–Carmona, M.F. Costa, D.F. Ventura, P.S. M. Barros; Grating Visual Acuity Development of Brazilian Terriers Using the Sweep–VEP Method . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4313.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: to measure the development of grating visual acuity (VA) in Brazilian Terrier pups by sweep visual evoked potentials (sVEP). Methods: Grating VAs of Brazilian Terrier pups (n=6; 3 male, 3 female), from the same litter and one adult (matrix) were measured. Sweep–VEPs (NuDiva) were recorded from two active electrodes placed on the scalp at O1 and O2, a reference electrode at Oz and a ground electrode at Cz. The stimuli were pattern reversal square wave gratings at a rate of 6Hz, ranging from .2 to 15 cicles per degree. The mean monitor luminance was 159.3 cd/m2. The VAs were measured weekly from the 4th to the 13th week. Viewing distance was 50cm and the pup was positioned on the lap of the investigator with the head gently supported to maintain the eyes in front of the video monitor (Dotronix D788). The test was performed in a darkened room without mydriatic, sedative or anesthetic drugs. Results: The mean VA ranged from 2.28±0.16 cpd (equivalent to 20/260 Snellen VA) at the 4th week to 8.59±0.13 cpd (20/70) at the 13th week. Adult VA was 8.7 cpd (20/70). This value was reached by the pups around the 10th week. VA increase was steeper up to the 7th week than afterwards. The rate of increase gradually declined up to the 10th week. An ANOVA comparing the weekly results showed significance for all results between the 4th and 10th weeks (f= 479.3 p< .001) and lack of significance thereafter. There was a high positive correlation between the VA and body weight (Pearson R= .92; p< .001). Thus the course of development of VA paralleled that of body weight, with a high rate of increase in the first 7 weeks, followed by declining rates. Conclusions: The Sweep–VEP method offers a rapid and reliable procedure for the quantification of grating VA in pups, without the need for sedation. Pup VA reached adult values at the 10th week of life. The adult VA measured (20/70) is in accordance with estimates of VA of dogs in other studies.
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