[Studies on the effect of checkerboard pattern on sensory and motor fusion]

We studied the fundamental effects of checkerboard pattern (CP) as fusional background on sensory and motor fusion to clarify the effectiveness of the checkerboard pattern stimulator (CPS), which clinically accelerates anti-suppression and bifoveal fusion in the treatment of manifest strabismus. We studied the size of CP which could generate motor fusion in order to eliminate artificial deviations induced by various powers of prism in Aulhorn's phase difference haploscope, with 20 normal subjects aged from 26 to 30 years old. Seven kinds of check sizes from 0.125 to 5 cycles/degrees (c/d) were presented. We found that a check size of 0.5 c/d or more (narrower check size) had no effect on horizontal motor fusion and that a check size of 1 c/d or more had no effect on vertical motor fusion. To remove suppression, it is important to produce only sensory fusion with the CP. Assuming that the lower limit of visual acuity for CPS is 0.05, the check size needs to be maintained approximately at 1.5 c/d. Our results suggest that a check size of 0.5 c/d for CPS is appropriate to promote sensory bifoveal fusion and stereopsis.