Electrophysiological Evidence of Adaptation to Colored Filters

Subjects wore blue filters (Kodak Wratten 45) in front of their normal spectacle correction for a period of 4.5 hr. Visual evoked potential (VEP's) were measured (monocularly) before, in white light and through the blue filters at the start and finish of wearing the filters. Predictably, from the chromatic interval, the subjects initially showed some degree of myopia, confirmed by more negative lens power required to give maximum VEP response. However, after 4.5 hr of wear of the filters, VEP's were measured again and it was found that the maximum VEP response was obtained in each case with less negative lens power, indicating adaptation of the visual system toward emmetropia. The role of accommodation in this adaptive process is discussed.