Amplitude of pupillary contraction as a function of intensity of illumination in schizophrenia

When the amplitude of pupillary contraction of normal, healthy adults was binocularly recorded as a function of increasing intensity of light-stimulation, a linear relationship was found between the amplitude and log intensity. Schizophrenic patients deviated significantly from this systematic response pattern in two ways. One group of patients (35%) manifested the same pupillomotor threshold as the normals, however, as the intensity of light was systematically increased mean amplitude and rate of pupillary contraction fell below that evidenced by normals. Another group of patients (65%) were distinguished by an abnormal pupillomotor threshold, specifically requiring an increase of one log intensity unit for the elicitation of a recordable pupillary contraction. Moreover, as the light intensity increased, the mean amplitude of contraction was significantly attenuated at all intensities below that of the normals and of the schizophrenics who manifested a normal pupillomotor threshold. In addition, it was found that the average diameter of the dark-adapted pupil was smaller in both groups of patients as compared to the healthy adults, although there was no difference between the patient groups on the variable. As pupillary reactivity to stress in normals is characterized by an increase in the diameter of the dark-adapted pupil representing increased sympathetic outflow and by a reciprocal increase in the diameter of the light-adapted pupil representing increased supranuclear inhibition, the results of the study do not support the assertion that schizophrenics are hyperaroused. It is suggested schizophrenia may be considered a tonic autonomic dysfunctional state of mock-arousal characterized by either abnormally high levels of central supranuclear inhibition or by defective sympathetic outflow, or both.