Pupil Cycle Induction Test: A Way of Evaluating the Pupillary Light Reflex

Abstract

The Pupil Cycle Induction Test (PCIT) described here is a simple and sensitive clinical method for the evaluation of afferent pupillary defect. It assesses the difficulty in setting up regular and sustained light-induced pupil oscillations, in contrast to methods assessing the light reflex by timing the oscillations. PCIT was applied to 186 presumably normal eyes (with normal visual acuity and normal fundi). In ten eyes, sustained oscillations could not be induced; further investigation showed that four of these eyes had altered visual-evoked response. The test was also carried out in 34 patients suffering from anterior visual pathway disorders. Sustained pupil oscillations could not be set up in 44 out of the 57 affected eyes. In the present series, significant alteration of light-induced pupil oscillations has been observed in several patterns: (1) immediate alteration; (2) delayed interruption of oscillations without spontaneous recovery, and (3) intermittent periods with oscillations of relatively small amplitude lasting more than three pupil cycles. PCIT assesses changes in light threshold for pupil response. It is suggested that delayed and transient alterations of oscillations are related to time-dependant afferent pupil defects similar to intermittent abnormalities of visual function reported in patients with diseases of the optic nerve or the chiasm.

Influence of Central Depressant Drugs on Pupil Function: An Evaluation with the Pupil Cycle Induction Test

“…Patterns of changes in oscillations were similar to those described in patients with anterior visual pathway disorders [1]; they have been classified into three groups: (1) immediate alteration; (2) delayed interrup tion of oscillations, without spontaneous re covery, and (3) prolonged pause periods. Striking reduction in amplitude of oscilla tions was moreover observed in 6 patients.…”

“…Compared to the re sults of PCIT in presumably normal eyes [1], this proportion is significant (p<0.001). No significant difference could, however, be demonstrated between chronic and occa sional users (p>0.05).…”

“…Subjects were tested in a dimly lit room (0.3-0.5 lx) and were given a 10-min adaptation time to ambient light when oscillations could not be induced at the first attempt. For further details of the method, see Safran et al [1],…”

“…The Pupil Cycle Induction Test (PCIT) is a simple clinical method for the evaluation of afferent pupillary defect [1], This test uses pupil oscillations induced by a fine beam of light projected in that it just overlaps the lower margin of the pupil. PCIT evaluates the difficulty in setting up regular and sus tained light-induced pupil oscillations, in contrast to methods assessing the light reflex by timing the oscillations [2][3][4][5][6][7][8], It has been evaluated as a diagnostic tool for patients with anterior visual pathway disorders and has been found to be simple and sensitive [ 1 ].…”

“…PCIT evaluates the difficulty in setting up regular and sus tained light-induced pupil oscillations, in contrast to methods assessing the light reflex by timing the oscillations [2][3][4][5][6][7][8], It has been evaluated as a diagnostic tool for patients with anterior visual pathway disorders and has been found to be simple and sensitive [ 1 ]. 1 Presented at the 6th International Congress of Neu rogenetics and Neuro-Ophthalmology, Zurich, June 9-12, 1981. Considering the effect of central nervous system depressant drugs on the pupil light reflex [9][10][11], as well as the extensive use of these drugs by the general population [12][13][14], the test was used to investigate pos sible alteration of pupil oscillations in sub jects taking these drugs.…”