Correcting presbyopia: the problem of pupil size

The pupil of the eye changes to as many different sizes as there are differences in the degrees of brightness and obscurity of the objects which present themselves before it. . .. In this case Nature has provided the visual faculty, when irritated by excessive light, with the contraction of the pupil, and here Nature works like one who, having too much light in his habitation, blocks up the window more or less according to necessity, and who, when night comes, throws open the whole of this window in order to see better. . ..