Effects of tobacco smoking on human ocular smooth pursuit

Objective: Test the hypothesis that nicotine-induced nystagmus results in reduced ocular smooth performance and pupil diameter in tobacco smokers. Methods: Twenty nonsmokers (age range, 20 to 45 years; mean age +/- SE, 31.5 +/- 1.7 years) and 14 smokers (age range, 17 to 50 years; mean age +/- SE, 30.6 +/- 2.6 years) were studied after a minimum of 2 hours of tobacco abstinence. Subjects were studied before and immediately after they inhaled air through a sham cigarette or after they smoked one of their preferred brand of cigarettes, respectively. Results: A very small, consistent, and statistically significant increase in smooth pursuit was found with both eyes to a 15 degrees per second moving target after one tobacco cigarette was smoked. This was due to improvement in left and not right eye smooth pursuit. The nonsmokers had no significant change in 15 degrees per second pursuit after sham smoking. Nonsmokers and smokers did not differ in left eye 6 degrees per second smooth pursuit before or after sham or tobacco smoking. The changes in right eye 6 degrees per second smooth pursuit were inconsistent and differed at various times between the two groups. During the smooth pursuit task the pupil diameter of the nonsmokers increased, but there was no change in the tobacco smokers. Black subjects had smaller baseline pupils than white subjects, unrelated to smoking status. Conclusions: Contrary to the hypothesis, tobacco smokers had a very small but significant improvement in left eye pursuit but no change in pupil diameter. Race-related differences in baseline pupil diameter were similar in both nonsmokers and smokers.