Transient effects of smoking on the eye

To investigate the immediate short-term effects of smoking in habitual smokers, on the tear film, pupil size and accommodative ability of the human eye.

Habitual smokers were tested within 5 min of smoking a cigarette. The tear film analysis was undertaken using tear break-up time (TBUT), tear lipid layer thickness and tears meniscus height (TMH) measurements. Three different ways of tear break-up time (TBUT) were used; using fluorescein; a non-invasive TBUT using tearscope; and a video captured method with a corneal topographer. Pupil size was measured objectively using the video capture on the corneal topographer. Accommodative ability was checked by performing a 'push up test' to measure amplitudes of accommodation (AoA) and by measuring defocus curves.

Forty-five participants were enrolled (mean age 22.0 ± 4.4 years). TBUT was reduced after smoking a cigarette with all three assessment methods and this reduction was statistically significant (p < 0.001). A reduction in lipid layer thickness was seen after smoking a cigarette with both methods used and was statistically significant (p < 0.01). A significant reduction in pupil size (p < 0.01) and in AoA (p < 0.001) was observed after smoking a cigarette. The difference in TMH and defocus curves, before and after smoking, were not statistically significant (p > 0.05).

The study shows that there is an immediate adverse effect of smoking on TBUT and AoA which seems to be very transient.