Switching control of accommodation: experimental and simulation responses to ramp inputs

The irregular staircase appearance of the accommodation response to a ramp stimulus, i.e. slow movement of a target toward the subject´s eye, suggests a switching between different states of control. Experiments and model simulations indicate that blur processing by the retina and cortex underlies threshold triggering of the switch. The ON state consists of a fairly high gain, closed-loop control system that minimizes error. The OFF state provides for a quasi-open loop state and slow drift to a bias level, under the influence of a leaky integrator.