Abstract
It is possible to explain a number of observations of visual adaptation to optical rearrangement and other visual effects as examples of the ‘Kohnstamm phenomenon’. This is the tendency for a stressed muscle to remain innervated for a period of time after cessation of the voluntary signal to relax. When this phenomenon operates with respect to eye muscles, it may be referred to as ‘eye-muscle potentiation’. Several studies and their results are presented that demonstrate eye-muscle potentiation effects on apparent visual distance. The implications of these studies for prism adaptation are discussed.