Smoking can cause an immediate decrease in TBUT.
Smoking can cause an immediate decrease in TBUT. Photo: Jennifer S. Harthan, OD, and Milton M. Hom, OD. Click image to enlarge.

Several studies have been conducted on the effect of smoking on the tear film and ocular surface, but few have been done on smoking and pupil size. In a recent study, researchers investigated the immediate short-term effects of smoking on the tear film, pupil size and accommodative ability of the human eye.

A total of 45 habitual smokers were tested within five minutes of smoking a cigarette. Tear film analysis evaluated tear breakup time (TBUT), tear lipid layer thickness and tear meniscus height. Pupil size was measured objectively using the video capture on the corneal topographer. Accommodative ability was evaluated through a pushup test to measure amplitudes of accommodation and by measuring defocus curves.

The study revealed that smoking can immediately decrease TBUT, alter the tear lipid layer, cause miosis of the pupil and reduce the amplitude of accommodation.

“A possible reason for short-term effects of smoking may be related to the short lifespan of nicotine, as nicotine rapidly changes into a less toxic and relatively inactive substance which may cause a reversal in any change caused by it,” the authors explained.

They also observed a 0.50D decrease in amplitude of accommodation measured after cigarette smoking. However, there wasn’t a significant decrease in subjective clear vision range by performing defocus curves before and after smoking exposure apart from the +1.50D and +1.00D lenses where the decrease was statistically significant.

“It can be hypothesized that smoking might alter the elasticity of lens zonules or ciliary muscles which then affect the accommodative ability of the eye similar to corneal prospective where smoking is associated with increased corneal rigidity,” the authors explained.

They believe this is the first study to report the acute effect of smoking on subjective accommodation of the eye without controlling for pupil size.

Latif N, Naroo SA. Transient effects of smoking on the eye. Cont Lens Anterior Eye. April 3, 2022. [Epub ahead of print].