Relative Effectivity of Foveal and Parafoveal Stimuli in Eliciting Fusion Movements

Abstract

Introduction Present opinion seems to be that stimuli presented to the peripheral retinas are more powerful in eliciting fusion movements than are stimuli presented to the foveas. In an annual review of the literature on strabismus, Parks,¹ when discussing an investigation by Nauheim,² says, "Peripheral fusion is stronger than central fusion. That this is so was not questioned...." Parks then proceeds to discuss an hypothesis to account for the superiority of the peripheral retina. Linksz³ in an annual review of optics and visual physiology quotes Nauheim's * statement that "paramacula targets represent a greater stimulus to fusion than do central targets...." Linksz comments, "(Only in case the author meant 'greater stimulus for fusion movements,' would one, somewhat reluctantly, agree.)" This belief in the dominance of the peripheral retina has, as its natural consequence, a strong influence on thought concerning strabismus and orthoptic training. Burian⁴ says, "I believe