Purpose: Remote ischemic conditioning (RIC) implies that transient ischemia in a limb can affect perfusion in a target organ elsewhere in the body. The changes in perfusion can be assumed to be paralleled by changes in the vessel diameters in the target organ. It remains to be elucidated whether the diameter of normal retinal vessels can be used as a marker of RIC in vivo.
Methods: In 20 normal persons aged 20 to 31 years the Dynamic Vessel Analyzer (DVA) was used to measure the resting diameter and diameter changes during isometric exercise and flicker stimulation before, immediately after, and 1 hour after RIC induced by transient ischemia in the left arm.
Results: The baseline diameter of retinal venules was reduced nonsignificantly immediately after (P = 0.07) and significantly 1 hour after RIC (P = 0.009), whereas the baseline diameter of arterioles was unaffected by the intervention (P = 0.61). Arterial constriction induced by isometric exercise was significantly reduced immediately after RIC (P = 0.04), but not 1 hour after RIC (P = 0.99). None of the other diameter responses were affected by RIC (P = 0.22 for all comparisons).
Conclusions: The diameter of retinal vessels might potentially be a marker of ischemic conditioning in the body in general. The effect of RIC on retinal vascular diseases where ischemia is a part of the pathogenesis should be investigated.