The Singular Vision of William Charles Wells (1757–1817)

Abstract

William Charles Wells retained an interest in vision throughout his life. His first book was on single vision with two eyes; he integrated vision and eye movements to determine principles of visual direction. On the basis of experiments and observations he formulated three principles of visual direction, which can readily be demonstrated. In the course of these studies, he also examined visual acuity, accommodation and convergence, visual persistence, and visual vertigo. Insights into visual processing were mainly derived from observations of afterimages that were used to provide an index of how the eyes moved. His experiments enabled him to distinguish between the consequences of active and passive eye movements (later called outflow and inflow) as well as describing nystagmus following body rotation. After providing a brief account of Wells's life, his neglected research on vision is described and assessed.

Two historical strands in studying visual direction1

“…The prediction from the belief is essentially that the direction of an object seen with either eye is veridical. (Adapted from Wade et al., 2011.)…”

“…When Hering turned to visual direction, in 1879, Wells had been forgotten. Hering essentially rediscovered Wells's Proposition I, although no reference was made to Wells's earlier enquiries (Ono, 1979, 1981; Wade, 2003; Wade et al., 2006; Wade, Ono, Mapp, & Lillakas, 2011). Hering (1879) referred to his observation illustrated in Figure 4 as demonstrating the law of identical visual directions, with which he has become eponymously linked.…”

A Brief History of Eye Movement Research

“…Wells mainly tested these propositions using pieces of coloured string and wire for the stimuli [17], however, his predictions and tests were not fully appreciated until much later on. Wells used afterimages and their apparent stability or motion as an index of whether the eyes moved as a result of voluntary or involuntary muscular activity, a method that was then widely used by ensuing researchers to investigate the effects of vertigo on eye movements and to investigate whether the eyes continue to move after body rotation has stopped.…”