The literature concerning the influence of drugs upon the iris, too voluminous to be presented here, can be grouped roughly into four categories, namely: (1) reports that dealt with the discovery and description of drugs or poisons, in which the pupillary effects were part of the general clinical findings; (2) investigations designed to reveal the mode of action of various drugs; (3) experiments in which drugs of known action were used to clarify the mechanism of physiological phenomena directly or indirectly related to pupillary movements; and (4) description and evaluation of drugs used in ophthalmology for the specific purpose of dilating or contracting the pupil.
In spite of the great popularity which the iris has enjoyed as an indicator in pharmacological experiments, the number of investigations in which the pupillary movements were registered accurately is relatively small. This fact and the great variations in drug responses between species, among individuals,
LOEWENFELD IE. The Iris as Pharmacologic IndicatorI. Effect of Physostigmine and of Pilocarpine on Pupillary Movements in Normal Man. Arch Ophthalmol. 1963;70(1):42-51. doi:10.1001/archopht.1963.00960050044010