How vernier acuity depends on contrast
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Updated: Aug 15, 2026

The Optokinetic Response as a Quantitative Measure of Visual Acuity in Zebrafish
Published on: October 9, 2013
1Department of Physiology and Anatomy, University of California, Berkeley 94720.
Abstract:
Vernier acuity was measured by finding the just discriminable offset for an edge separating fields of different luminances. The contrast of this stimulus is easily specified by the formula c = (Lstim - Lsur)(Lstim + Lsur). Vernier thresholds are about 4-5 sec of arc for contrasts 0.22 and higher, but increase exponetially with decreasing contrast. By comparison, the presence of the stimulus could be detected at a contrast of 0.016. The possible role of the magnocellular and parvocellular pathways in carrying the input signals to the fine localization process is discussed.
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