Purchase this article with an account.
Naveen K. Yadav, Diana P. Ludlam, Kenneth J. Ciuffreda; Effect of Different Stimulus Configurations on Visually Evoked Potential (VEP) Amplitude. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6083.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To assess the effect of different stimulus configurations on the amplitude of the pattern visual evoked potential (VEP).
VEP amplitudes were assessed for three stimulus configurations: (1) central circular stimulus increasing incrementally in radius from 0.5 to 7.5 degrees in 6 steps, (2) central annular stimulus with the inner radius increasing incrementally from 0.5 to 7.5 degrees in 6 steps, and (3) simulated hemi-field (right, left) and quadrant (upper right, upper left, lower right, lower left) visual field defects. Five visually-normal adult subjects (ages 21 to 68 years) with 20/20 corrected visual acuity were tested using each stimulus configuration. The DIOPSYS NOVA - TR VEP system was used, with 3 electrode placement (ISCEV standard). Subjects viewed the test field binocularly at a distance of 1 meter. A checkerboard test pattern (64 X 64 black and white checks, 85% contrast, 64 candela per square meter luminance, and 2 Hz temporal frequency) was used. 5 test trials for each stimulus configuration were conducted, each on a separate day to assess response repeatability, in a counterbalanced manner. Changes in the group mean amplitude were used for the primary analysis.
For the circular stimulus, there was a linear increase in the amplitude (y = 0.776 x + 2.14) (r = 0.989) with increase in stimulus area. Similarly, for the annular stimulus, there was a linear decrease in the amplitude (y = -0.796 x + 16.76) (r = 0.980) with decrease in stimulus area. For the simulated hemi and quadrant visual field defects, response amplitude was significantly greater for the simulated quadrant than the hemi-field defect, but it was only linearly additive in 3 of the 5 subjects. For nearly all changes in stimulus configuration, there was no significant change in latency.
The results of this study suggested linear summation of the cone-mediated VEP response to the circular and annular stimulus area changes. The quadrant field findings suggested greater individual variability than for the other 2 stimulus configurations. The results of the study will be used to develop protocols for objectively assessing residual visual field functionality in ocular and neurological conditions such as, glaucoma, macular degeneration, retinitis pigmentosa, stroke, and traumatic brain injury.
This PDF is available to Subscribers Only