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

Abstract

Afferent pupillary defect is an early sign of optic nerve or chiasm disease. It can be evaluated by the Pupil Cycle Induction Test (PCIT) which assesses the difficulty in setting up regular and sustained pupil oscillations. PCIT was carried out in 30 subjects with presumably normal visual function (normal visual acuity and normal fundi) and taking benzodiazepines and/or barbiturates. In 42 out of the 60 tested eyes, response to PCIT was altered. This emphasizes the necessity of a detailed drug-taking history when investigating anterior visual pathways by means of pupil function, especially when one considers the extensive use of central nervous system depressant drugs by the general population.

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

“…We shall report in another paper on the influence of benzodiazepines and bar biturates on the response to PCIT [27], This will emphasize the importance of a careful drug-taking history when investigating ante rior visual pathways by means of pupil func tion.…”

Effects of centrally depressant drugs on pupillary function: significance for normal and diseased subjects.

“…Ninetyfour per cent of them exhibited induced pupillary oscillation that lasted for more than two runs of 40 successive cycles (Safran et al, 1981a). When this examination technique was applied to the 60 eyes of 30 unselected subjects with normal visual function, but undergoing a benzodiazepine or barbiturate treatment, in 30% only more than 40 oscillations could be obtained (Safran et al, 1981b). In view of this open study, we recently performed a controlled experimental study with volunteers receiving 6 mg of bromazepam a day, using a similar method of pupillary evaluation.…”

“…Third, since modification in pupil response due to depressant drugs is sometimes difficult to distinguish from that due to optic nerve disorders (Safran et al, 1981b), a detailed drugtaking history is necessary when investigating anterior visual pathways by means of pupil function. Unfortunately, the possibility of modification in pupillary function due to the ingestion of central depressant drugs is often overlooked in clinical practice.…”

The measurement of pupil cycling time

“…The clinical use of pupil cycling has been extensive, and abnormal PCTs have been reported in various conditions where neurological changes might be expected. These include optic neuritis [14,27,37], myasthenia gravis [9,11,19], HIV infection [21,32], optic nerve compression [38], space-occupying lesions [23], central depressant drugs [31], multiple sclerosis [24,27,40], optic neuropathy [10,23,29], primary closed-angle [8] and open-angle [30] glaucoma, ocular hypertension [9], diabetes [6], progressive autonomic failure [7], Horner's syndrome [2], leprosy [17], gastrooesophageal reflux [5], familial dysautonomia [13] and Graves' disease [16] . Since pupil cycling is reported to be unaffected by timolol, it has been suggested [18] that PCT could be used to investigate cases of open-angle glaucoma.…”