Binocular summation improves performance to defocus-induced blur

Sotiris Plainis, Dionysia Petratou, Trisevgeni Giannakopoulou, David A. Atchison, Miltiadis K. Tsilimbaris

    Research output: Contribution to journalArticlepeer-review


    PURPOSE. To assess whether there are any advantages of binocular over monocular vision under blur conditions. METHODS. The effect of defocus, induced by positive lenses, was measured on the pattern reversal visual evoked potential (VEP) and on visual acuity (VA). Monocular (dominant eye) and binocular VEPs were recorded from 13 volunteers (average age, 28 ± 5 years; average spherical equivalent, -0.25 ± 0.73 D) for defocus up to 2.00 D using positive powered lenses. VEPs were elicited using reversing 10 arcmin checks (4 reversals/s). The stimulus subtended a circular field of 7° with 100% contrast and mean luminance 30 cd/m 2. VA was measured under the same conditions using ETDRS charts. All measurements were performed at 1 m viewing distance with best spectacle sphero-cylindrical correction and natural pupils. RESULTS. With binocular stimulation, amplitudes and implicit times of the P100 component of the VEPs were greater and shorter, respectively, in all cases than for monocular stimulation. Mean binocular enhancement ratio in the P100 amplitude was 2.1 in focus, increasing linearly with defocus to be 3.1 at +2.00 D defocus. Mean peak latency was 2.9 ms shorter in focus with binocular than for monocular stimulation, with the difference increasing with defocus to 8.8 ms at +2.00 D. As for the VEP amplitude, VA was always better with binocular than with monocular vision, with the difference being greater for higher retinal blur. CONCLUSIONS. Both subjective and electrophysiological results show that binocular vision ameliorates the effect of defocus. The increased binocular facilitation observed with retinal blur may be due to the activation of a larger population of neurons at close-to-threshold detection under binocular stimulation. © 2011 The Association for Research in Vision and Ophthalmology, Inc.
    Original languageEnglish
    Pages (from-to)2784-2789
    Number of pages5
    JournalInvestigative Ophthalmology and Visual Science
    Issue number5
    Publication statusPublished - Apr 2011


    • adult
    • article
    • binocular vision
    • blurred vision
    • defocus
    • evoked visual response
    • female
    • human
    • imaging
    • latent period
    • male
    • monocular vision
    • priority journal
    • sensory system electrophysiology
    • spectacles
    • visual acuity
    • visual stimulation
    • Adult
    • Evoked Potentials
    • Visual
    • Female
    • Humans
    • Male
    • Pattern Recognition
    • Refractive Errors
    • Retina
    • Vision
    • Binocular
    • Monocular
    • Visual Acuity
    • Young Adult


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