Retinal blood flow during dynamic exercise

Background: Exercise acutely lowers intraocular pressure (IOP) and raises arterial pressure. We wondered whether the resultant increase in ocular perfusion pressure would alter retinal blood flow. Methods: To investigate this question, 11 healthy volunteers each performed progressive cycle ergometer exercise until exhaustion was reached in 5-10 min. Immediately after exercise, retinal blood flow and arteriovenous passage time were determined by video fluorescein angiography. Ten other volunteers performed repeated episodes of cycle ergometer exercise at approximately 60% of the maximal aerobic capacity, immediately prior to estimates of macular leukocyte velocity and density via blue-field stimulation. Results: Progressive exercise lowered IOP and elevated calculated ocular perfusion pressure. Within the retinal circulation, this exercise tended to raise mean dye velocity, as it significantly narrowed the superior temporal artery and vein; as a result, calculated retinal blood flow was unchanged. Simultaneously, retinal arteriovenous passage time was substantially shortened. Blue-field simulation showed that exercise increased macular leukocyte velocity while leaving leukocyte density unchanged. Conclusions: These results show that the normal retinal hemodynamic response to increases in perfusion pressure on dynamic exercise includes vasoconstriction that normalizes flow and faster capillary and overall retinal blood transit.