Purchase this article with an account.
J. C. Leaney, A. Klistorner, H. Arvind, S. L. Graham; Binocular Cortical Suppression Measured in Central vs. Peripheral Field Using Dichoptic Multifocal VEP - Implications for Scotoma Detection. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5487.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To assess binocular interaction at different eccentricities using a novel binocular simultaneous multifocal VEP system.
A pattern onset blue on yellow checkerboard using sparse presentation, cortically scaled for eccentricity, was presented dichoptically. The minimum time shift between the stimulation of the same area of visual field of each eye was 120msec. The subject perceived only one image. A monocular then binocular recording demonstrated the degree of binocular suppression for each patient. 30 normals, VAc >6/6 corrected, steroeacuity >60secs arc, and full standard automated perimetry testing, underwent dichoptic VEP assessment to establish normal asymmetry coefficients. Of these, 10 subjects were tested with spherical lenses applied to one eye (+4, +6D). The change in local VEP amplitudes was determined for each eye at 5 rings of increasing eccentricity.
Dichoptic recording is associated with a 20% mean reduction in amplitude due to inter-ocular suppression. With progressive visual blur there was additional reduction of central more than peripheral signals, while in the unaffected eye there was signal enhancement (release of suppression). For the inner 2 rings (~10 degrees) at 6D of blur there was an average of 60+/-9% reduction for the centre ring and 54+/-7% for the next ring while 4D produced reductions of 45%+/-15% and 34+/-18% respectively. Rings 3 to 5 showed diminishing amounts of suppression with eccentricity but were still statistically significant. The contralateral release of suppression was around half of the suppression of the blurred eye, with a 28+/-16% (6D) and 23+/-11%(4D) increase in amplitude for the central ring of the normal eye.
Dichoptic multifocal VEP recording demonstrates binocular suppression. Increasing visual blur not only reduces the signal in the affected eye but shows enhancement of signal in the fellow eye (central>peripheral). This phenomenon could lead to increased inter-eye asymmetry of responses occurring in early disease states, but mainly in the paracentral field locations.
This PDF is available to Subscribers Only