The effect of ocular warming on ocular circulation in healthy humans

Objective: To examine the effect of ocular warming on retinal blood flow (RBF) and subfoveal choroidal blood flow (CBF) in humans. Methods: Ocular warming was induced in 10 healthy volunteers using an ocular warming lamp for 10 minutes. The ocular surface temperature was measured before and after warming. The RBF in the retinal artery and vein and the CBF in the foveal region were examined with a retinal laser Doppler velocimetry system and a laser Doppler flowmeter, respectively. Ocular blood flow measurements were performed before and 3, 6, and 9 minutes after warming. Results: The ocular surface temperature significantly increased just after warming and returned to baseline 10 minutes later. Three minutes after warming, the meant +/- SE RBF significantly increased in the retinal artery (14.2% +/- 3.5%, P = .01) and vein (15.8% +/- 3.6%, P = .006). Six minutes after warming, the RBF returned to baseline in the artery and vein. Three and 6 minutes after warming, the meant SE CBF significantly decreased 16.6% +/- 4.2% and 24.2% +/- 4.7%, respectively (P = .001 for both). Nine minutes after warming, the measurements returned to baseline. Conclusions: The RBF increased and the CBF decreased in the foveal region after cessation of ocular warming in healthy young volunteers. The CBF in the foveal region may contribute to maintaining a constant retinal temperature in response to ocular warming.