A linear chromatic mechanism drives the pupillary response

Previous studies have shown that a chromatic mechanism can drive pupil responses. The aim of this research was to clarify whether a linear or non-linear chromatic mechanism drives pupillary responses by using various colours of test stimuli defined in cone-contrast space. Pupil and accommodation responses evoked by these test stimuli were continuously and simultaneously measured objectively by photorefraction. The results with isochromatic and isoluminant stimuli showed that the accommodative level remained approximately constant (