Stability of the accommodative dark focus after periods of maintained accommodation.

The behavior of the accommodative system at rest was investigated following short- (5 min) and long-term (1 hr) accommodative stimuli of either 0.00 D or 3.00 D. The resting position of accommodation changed in the direction of the accommodative stimulus presented. After the 5 min stimulus, the resting position slowly returned toward the pre-stimulus level. After the 1 hr stimulus, the resting state remained significantly different from the pre stimulus level over the subsequent 6 hr. These results suggest that the equilibrium level of accommodation in the dark is determined by a balance of the previous accommodative stimuli.