The acute effects of cigarette smoking on human optic nerve head and posterior fundus circulation in light smokers.

Abstract

To study the acute effects of cigarette smoking on tissue circulation in the optic nerve head (ONH) and posterior fundus in smokers with a short smoking history. Ten healthy smokers whose length of smoking history was within 2 years (age 25 +/- 1 years; smoking index (number of cigarettes smoked per day x length of smoking history in years) 16 +/- 4, mean +/- SE) were included in the study. Using the laser speckle method, normalised blur (NB) value, a quantitative index of tissue blood velocity, was measured every 0.125 s and averaged over three pulses across an area located in the temporal site of the ONH free of visible surface vessels (NBONH) and across an area located halfway between the macula and the ONH with no discrete vessels visible (NBch-ret). NBONH, NBch-ret and intraocular pressure (IOP) in one randomly chosen eye, and blood pressure (BP) and pulse rate (PR) were measured before, and 1, 5, 10, 15, 20, 25, 30, 45, 60 and 90 min after sham smoking. One week later, NBONH, NBch-ret and IOP in the same eye, and BP and PR were measured after cigarette smoking according to the same time schedule as in the control experiment. After sham smoking, no parameter showed a significant change during the experiment. Differences in NBONH from the baseline were not significant between the smoking experiment and sham smoking experiment, while NBch-ret showed a significant difference at 30 min. Inter-group difference in the time course of the difference from baseline was significant (ANOVA, p = 0.0246, 0.0021). BP and PR were significantly increased between 1 and 20 min after smoking while IOP showed no significant change at any time of measurement. In light smokers, cigarette smoking showed little effect on tissue blood velocity in the ONH and slightly decreased that in the posterior fundus, suggesting a significant increase in vascular resistance in these tissues.