Effects of Tobacco Smoking on the Kinetics of the Pupillary Light Reflex: A Comparison between Smokers and Non-Smokers

Abstract

Background: The time course of the pupillary light reflex (PLR) is determined by the successive activation of parasympathetic and sympathetic innervations of the iris, latency and amplitude reflecting parasympathetic activity and recovery time showing mainly sympathetic activity. Objective: To determine the effects of tobacco cigarette smoking on the PLR in smokers after an abstinence period of at least 12 h. Methods: Ten smokers (mean 15.7 cigarettes/day) and 10 non-smokers participated in a randomised, non-intervention controlled, cross-over study that included a parallel control group. Smokers underwent two sessions with a time interval between 3 and 8 days; two recordings were taken at each session, separated by 20 min: session 1, without smoking, and session 2, smoking 3 cigarettes within a 30-min period. Non-smokers underwent one session; two recordings were taken separated by 20 min. At each recording, in both groups, PLR was elicited with four light flashes of increasing luminance. Results: The relationship between PLR parameters and light intensity was linear in each subject. The slope of the regression line for relative amplitude increase versus intensity was significantly flatter in abstinent smokers than in non-smokers (p = 0.033); the slope returned significantly after smoking (p = 0.043). No other significant effects were obtained. Conclusions: Kinetic parameters of PLR provide a sensitive pharmacological test to detect cholinergic neurotransmission manipulation effects, as they seem to detect changes in moderate smokers after 12 h of abstinence, and their reversal on return to smoking. These results suggest an enhancement in the suppression of the parasympathetic oculomotor reflex arc rather than a facilitation of the sympathetic drive to the iris.

Clinical factors affecting pupillary light reflex parameters: a single‐centre, cross‐sectional study

“…However, only a few PLR studies have adjusted for individual variability. 6,10,13,14 Several previous investigations have examined the effects of clinical factors such as light stimulus intensity, 5,15-19 age, 5,20,21 sex 20,22,23 and tobacco smoking 24,25 on PLR parameters. A number have reported the effects of different light stimulus intensities on PLR parameters which were consistent with the findings of the present study; higher light stimulus intensity increased ACV, 6,10 MCV 5,6,10,15 and DELTA, 6,10 shortened LAT 5,6,10,15 and prolonged T75.…”

Parasympathetic Nervous System Dysfunction, as Identified by Pupil Light Reflex, and Its Possible Connection to Hearing Impairment

“…Although the technical demands of PLR measurement are relatively straightforward, it is also worth mentioning that PLR is a test that might be influenced by many factors other than those one wishes to study. The characteristics of the light stimuli [ 90 ], gender [ 91 ], smoking [ 92 ], alcoholism [ 93 ] and even the color of iris [ 94 ] could influence the test result. Many studies in our review failed to report these factors.…”

“…Moreover, researchers have also tested pupil light reflex on psychiatric disorders like Schizophrenia [ 6 ] and anxiety disorder [ 7 ]. In addition, the pupil light reflex has been found to be sensitive to aging [ 8 ], smoking [ 9 ] and gender [ 10 ].…”

Altered face scanning and arousal after orbitofrontal cortex lesion in adult rhesus monkeys.

“…Further, although the initial pupil diameter (values during the first 100 ms of each picture presentation) did not significantly vary between groups, individual variations were important. To correct for these variations (Morte et al, 2005), the amplitude of the pupillary responses was adjusted in relation to the initial pupil diameter for each animal and for each category of pictures. This correction also allows for controlling of potential effects of screen illumination.…”