<prompt> Visual cycle refers toDay vision and colour visionCycle of night vision and colour visionAlternate distance and near fixationPhotodecomposition and regeneration of visual pigments  <response>: Visual cycle In the retina of living animals, under constant light stimulation, a steady state must exist under which the rate at which the photochemicals are bleached is equal to the rate at which they are regenerated. This equilibrium between the photodecomposition and regeneration of visual pigments is referred to as visual cycle. Reference :- A K KHURANA; pg num:-14,15 