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The effects of tobacco smoking on smooth pursuit eye movements
P A Sibony1, C Evinger, K A Manning
1Department of Ophthalmology, State University of New York, Stony Brook 11794.
Abstract:
It has recently been shown that tobacco smoking in normal human subjects induces a transient primary-position upbeat nystagmus. We studied the effects of tobacco smoking on smooth pursuit eye movements and found defects in both vertical and horizontal tracking during the first 5 minutes after smoking one cigarette. The smooth pursuit defect consisted of a reduction in upward tracking velocity and the superposition of saccadic square-wave jerks on both vertical and horizontal tracking eye movements. The degree of impairment in upward smooth pursuit correlated with the intensity of tobacco-induced nystagmus present when recording in darkness. We suggest that these alterations are due to summation of nystagmus on normal tracking eye movements rather than primary defects in the smooth pursuit system.
Insights
Tobacco smoking temporarily impairs smooth pursuit eye movements in humans, causing jerky tracking. This defect, particularly in upward gaze, is linked to smoking-induced nystagmus.
Area of Science:
- Neuroscience
- Ophthalmology
- Human Physiology
Background:
- Tobacco smoking is known to induce transient primary-position upbeat nystagmus in healthy individuals.
- The impact of smoking on the dynamic aspects of eye movements, such as smooth pursuit, remains less understood.
Purpose of the Study:
- To investigate the effects of tobacco smoking on smooth pursuit eye movements in normal human subjects.
- To determine the relationship between smoking-induced nystagmus and smooth pursuit deficits.
Main Methods:
- Assessed smooth pursuit eye movements (horizontal and vertical) in participants after smoking one cigarette.
- Quantified tracking velocity and analyzed saccadic intrusions (square-wave jerks).
- Correlated smooth pursuit impairment with the intensity of primary-position upbeat nystagmus recorded in darkness.
Main Results:
- Smoking caused significant defects in both vertical and horizontal smooth pursuit within 5 minutes.
- Observed were reduced upward tracking velocity and superimposed saccadic square-wave jerks during tracking.
- The severity of upward smooth pursuit impairment correlated positively with the intensity of smoking-induced nystagmus.
Conclusions:
- Tobacco smoking acutely impairs smooth pursuit eye movements, affecting both horizontal and vertical tracking.
- The observed deficits are likely caused by the summation of induced nystagmus onto normal tracking, not primary pursuit system dysfunction.
- Findings highlight the neurophysiological impact of smoking on visual-motor control.