<prompt> In dark adaptation, there is:Break down of rhodopsinIncreased threshold for visionNo role for conesNo change in the dioptric power of the eye  <response>: In dark adaptation, there is re-synthesis of the bleached rhodopsin. In the retina, the storage form of vitamin A all-trans retinol is conveed to 11-cis retinal which combines with opsin to form rhodopsin. Initial dark adaptation is due to cones; cones form visual pigment faster as compared to rods. Other changes in the dark: 1 dilation of pupil, 2 increased number of impulses in the optic nerve fibers. 