The effect of instilling adrenalin chloride into the mammalian eye

Abstract

Certain writers have concluded that mydriasis cannot be produced by instilling adrenalin into the eye of higher animals except under pathological conditions such as lesions of the pancreas or the removal of the superior cervical ganglion. Perhaps this conclusion results from an oversight of the antagonism existing between the influence of instilled adrenalin and light stimuli when simultaneously acting upon the intact eye. At any rate the conclusion is not supported by more recent experiments and is misleading when used as a basis for diagnosing certain pathological conditions.

I have found that mydriasis can be produced in these animals with relative ease and certainty. In making a comparative study, however, of different degrees of susceptibility to adrenalin, due care must be taken to keep the intensity of light stimuli constant. This is essential, since in the eyes of higher mammals where the light reflex is well developed, strong light may cause the pupil to constrict to such an extent that any antagonism of this process by adrenalin may be lost sight of. For instance, by instilling adrenalin into the normal cat eye for some minutes and then examining the eye in light bright enough to constrict the untreated eye to a small slit-like aperture, no difference in the drugged and undrugged eyes can be detected; but the same eyes examined in a dark corner may show a distinct difference in the pupils, the drugged pupil dilating more than the normal one. Thus the early dilating effect of adrenalin can be detected more easily by reducing the intensity of the light stimuli. In this preliminary communication, however, it is not so much the time of initial dilation as it is the time required for complete antagonism of the light stimuli by adrenalin that is considered.