Threshold and Rate of Dark Adaptation as Functions of Aǵe and Time 1

In order to describe one family of dark adaptation curves obtained from an age sample ranging from 16 through 89 years, a mathematical model of the form

was derived.

It was found that the model could be generalized. In addition it was concluded that threshold of dark adaptation as a function of time was lawfully related to chronological age.

Rate of adaptation was determined by differentiating the equation at time 30 sec and time 6 min as follows:

The results showed that rate of dark adaptation was a curvilinear function of age.

These findings are consistent with the hypotheses that dark adaptation threshold and rate of dark adaptation depend upon basic underlying physiological processes that change with age.