Effects of isometric exercise on subfoveal choroidal blood flow in smokers and nonsmokers.

PURPOSE Little is known about potential effects of smoking on ocular blood flow regulation. In the present study, the hypothesis was that choroidal blood flow (CBF) changes during an increase in ocular perfusion pressure induced by isometric exercise are altered in chronic smokers. METHODS The study was performed in 24 (12 smokers and 12 nonsmokers) healthy male volunteers in an observer-masked, two-cohort study design. The difference in CBF regulation between smokers and nonsmokers was tested during isometric exercise over a period of 6 minutes. CBF was assessed with laser Doppler flowery (LDF), and ocular perfusion pressure (OPP) was calculated from mean arterial pressure (MAP) and intraocular pressure (IOP). RESULTS Six minutes of isometric exercise induced a significant increase in MAP, pulse rate (PR), OPP, and CBF in smokers and nonsmokers (each P<0.001). The increase in CBF was significantly higher in the smoking group (P<0.001) than in the healthy control group, whereas a comparable increase in MAP (P=0.18), PR (P=0.18), and OPP (P=0.43) occurred in smokers and nonsmokers. IOP remained unchanged during isometric exercise in both groups. Moreover, in smokers, CBF started to increase at OPPs more than 49% above baseline, whereas CBF in nonsmokers remained stable until an increase in OPP of 74% over baseline. This difference between the two groups was significant (P<0.001). CONCLUSIONS These data indicate abnormal CBF regulation in chronic smokers compared with age-matched nonsmoking subjects during isometric exercise. The pathways responsible for this abnormal blood flow response remain to be elucidated.