Effect of refractive error on visual evoked potentials with pattern stimulation in dogs

Abstract

The purpose of this study was to investigate the effects of refractive error on canine visual evoked potentials with pattern stimulation (P-VEP). Six normal beagle dogs were used. The refractive power of the recorded eyes was measured by skiascopy. The refractive power was corrected to −4 diopters (D) to +2 D using contact lens. P-VEP was recorded at each refractive power. The stimulus pattern size and distance were 50.3 arc-min and 50 cm. The P100 appeared at almost 100 msec at −2 D (at which the stimulus monitor was in focus). There was significant prolongation of the P100 implicit time at −4, −3, 0 and +1 D compared with −2 D, respectively. We concluded that the refractive power of the eye affected the P100 implicit time in canine P-VEP recording.

Effects of pupil size on canine visual evoked potential with pattern stimulation

“…VEP is classified into flash-stimulated VEP (F-VEP), which uses a flash stimulus, and pattern-stimulated VEP (P-VEP), which uses a contrast-reversing checkerboard pattern stimulus. In our previous studies, the effects of the refractive power of the eye [10] and anesthesia [9] on canine P-VEP were reported, and we measured canine visual acuity using P-VEP [17].…”

Measurement of visual acuity in Beagle dog by visual evoked potential with pattern stimulation

“…For P-VEP recording, needle electrodes (VEP needle electrodes, Mayo Corp., Nagoya, Japan) were positioned at the inion (external occipital pro- tuberance) as the recording electrode and the nasion (nasal point) as the reference electrode. A plate-type electrode (LE ear electrode, Mayo Corp.) was positioned on the inner surface of the right auricle as an earth electrode, as in previous reports [ 2 , 3 , 4 ] ( Fig. 1

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“…Since we had not considered the refractive power of the eye in previous study, so we thought that the results differ from present study. After that, we reported that refractive power of the subject’s eye affects P-VEP wave form [ 3 ], so we recorded P-VEP after correction of refractive power of subject’s eye in this study. Refraction in an eye is the change in direction of light when light passes from the optic media toward the retina [ 6 ].…”

“…The refractive power indicates the degree of the defocusing of light on the retina. In previous study, it was reported that the P100 appeared at almost 100 msec as corrected refractive power to stimulus distance, while significant prolongation of the P100 implicit time was detected when the refractive power was defocusing to stimulus monitor [ 3 ]. In present study, P-VEP was recorded the eyes correcting refractive power, so we were able to measure the visual acuity of a dog not affected by refraction.…”

Grating Visual Acuity in phakic, aphakic, and pseudophakic Poodles

“…34 Another study regarding pattern VEP has observed that the refractive power correction directly interferes in the P100 wave latency. 35 This study demonstrated that VEP is a useful tool for assessing the grating VA of Poodles. Moreover, the 41D IOL implant is effective in improving VA after phacoemulsification, in comparison with that to the aphakic group and which is similar to that of the normal eye.…”