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18 2. Pupillary reactions elicited from the fovea and from the retinal periphery 53 (a) Influence of experimental procedure 56 (b) Criteria of pupillary responsiveness 57 (c) Pupil perimetry 57 Stimulus Color 58 1 . The literature 58 2 . Pupillary spectral sensitivity 60 Other Features of Pupillary Reactions to Light 65 1. Adaptation 65 (a) Adaptation to darkness 65 (b) Light adaptation 65 2. Effect of the entrance pupil 67 3. Binocular interaction 67 THE PUPILLARY REACTION TO NEAR VISION 69 CONCLUSIONS 77 BIBLIOGRAPHY , 80 As in all chapters of the literature on the pupil, there have been controversies concerning the role of the pupil in connection with both (1) the perception of light and (2) near vision. The chief questions raised about the first subject relate to the identity of the receptors for the light reflex: even today some authors hold that the rods play no pupillomotor role, while at the same time, the pupillary spectral sensitivity has been reported to show a scotopic curve even under photopic conditions (Bouma, 1962). As to near vision, the relations between accomodation, con- vergence, and the pupil have been discussed at length. It is the purpose of the present paper to give a reasonably concise experimental review of this literature, and to see what general conclusions can be drawn from it at this time. Criteria for Selection of Papers In all surveys of the literature, reviewers are faced with two main difficulties: they have to decide where to draw the limits that will outline the subject at hand most effectively, and they have to bear the nagging awareness that their material may be not at all complete. Were there more time to search for additional material, a large group of papers of most direct interest might be discovered around the next corner.. . In the present case, then, the publications presented are the ones available to the author at this time, which have as their chief subject either pupillary movements related to the retinal receptor mechanism, or pupillary movements related to near vision. It should
19 be stressed especially that exclusion or inclusion of a particular paper in this review should not be interpreted as implying an evaluation of its importance. Papers not represented were either missed or they were excluded because they appeared to fall outside the intentionally narrow limits imposed (Table 1). TABLE 1 Criteria for Selection of Papers I. Included: II. Excluded: (1) Methods of stimulation by light or near vision; (2) pupillary movements, as related to (a) different parameters of light stimulus, or (b) various factors of near vision reaction. (1) Methods for measuring pupillary size or movements; (2) experiments with chief emphasis on anatomy or physiology of afferent or efferent nerve paths, nervous centers, or effector muscles; (3) experiments with chief emphasis on physiological mechanisms involving the pupil, such as effects of drugs, altitude, gravity, rotation, changes in physiological state (respiration, heart rate, etc.), aging, fatigue;* (4) experiments in which the pupil is considered only in its role as part of an optical system; (5) psychological work concerned with conditioning, dis- comfort, etc.; (6) statements in general texts, without special experi- mental work of the author. * Because fatigue and emotional excitement are all-pervading mechanisms which cannot be avoided in experiments on conscious human beings or animals, their modifying effect on pupillary reflexes is noted; work primarily concerned with other aspects of fatigue has been excluded. It had been attempted, at first, to limit the review to those papers which contained more elaborate experimental material still applicable today, excluding works of chiefly clinical emphasis, especially when only simple instruments were used, and when they appeared outdated. It was, however, too difficult to draw the line between the mainly experi- mental and the mainly clinical, and the experiment classed as "simple" today may have been revolutionary and most important historically. In addition, the titles of some publications imply more elaborate physio- logical work than is actually contained in them, and it was felt that it might be useful to find such papers listed among the simpler experiments of a particular group.