Grating visual acuity development of brazilian terriers dogs using the sweep visual evoked potential method

Author(s)

Francisco Manuel Moreno Carmona

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2004-08-04

Examining board members

Paulo Sergio de Moraes Barros; Solange Rios Salomão; Dora Selma Fix Ventura

• Advisor: Paulo Sergio de Moraes Barros

Abstract

Our aim in this study was to measure the development of grating visual acuity (VA) in Brazilian Terrier puppies by sweep visual evoked potentials (sVEP). Grating VAs of 18 Brazilian Terrier dogs, 14 puppies (8 male, 6 female), from two different litters and 4 adults (2 male, 2 female), including the 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 6 Hz, ranging from 0.2 to 12 cycles per degree (cpd). 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. The median VA ranged from 2.28 cpd (Q2= 2.12; Q3= 2.36) (equivalent to 20/265 Snellen VA) at the 4th week to 9.18 cpd (Q2= 8.64; Q3= 9.31) (20/65) at the 13th week. The median of adult VA was 8.82 cpd (Q2= 8.71; Q3= 8.94) (20/70). This value was reached by the puppies 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 (&chi;2= 120.61; p< 0.001). The VAs were statistically different witch four week (Dunn\'s Method; p< 0.05). There was a high positive correlation between the VA and body weight (R= 0.83; p< 0.001; Spearman Rank Order Correlation). The Sweep-VEP method offers a rapid and reliable procedure for the quantification of grating VA in puppies and adults dogs, without the need for sedation. Pup VA reached adult values at the 10th week of life. The mean of adult VA measured (20/70) is in accordance with estimates of VA of dogs in other studies. The range of VA of Brazilian Terrier dogs were 8.60 cpd (20/70) to 9.57 cpd (20/60). (AU)