Ocular blood flow decreases during passive heat stress in resting humans

Tsukasa Ikemura, Akane Miyaji, Hideaki Kashima, Yuji Yamaguchi, Naoyuki Hayashi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Background: Heat stress induces various physiological changes and so could influence ocular circulation. This study examined the effect of heat stress on ocular blood flow.Findings: Ocular blood flow, end-tidal carbon dioxide (PETCO2) and blood pressure were measured for 12 healthy subjects wearing water-perfused tube-lined suits under two conditions of water circulation: (1) at 35°C (normothermia) for 30 min and (2) at 50°C for 90 min (passive heat stress). The blood-flow velocities in the superior temporal retinal arteriole (STRA), superior nasal retinal arteriole (SNRA), and the retinal and choroidal vessels (RCV) were measured using laser-speckle flowgraphy. Blood flow in the STRA and SNRA was calculated from the integral of a cross-sectional map of blood velocity. PETCO2 was clamped at the normothermia level by adding 5% CO2 to the inspired gas. Passive heat stress had no effect on the subjects' blood pressures. The blood-flow velocity in the RCV was significantly lower after 30, 60 and 90 min of passive heat stress than the normothermic level, with a peak decrease of 18 ± 3% (mean ± SE) at 90 min. Blood flow in the STRA and SNRA decreased significantly after 90 min of passive heat stress conditions, with peak decreases of 14 ± 3% and 14 ± 4%, respectively.Conclusion: The findings of this study suggest that passive heat stress decreases ocular blood flow irrespective of the blood pressure or arterial partial pressure of CO2.

Original languageEnglish
Article number23
JournalJournal of physiological anthropology
Issue number1
Publication statusPublished - 2013 Dec 6
Externally publishedYes


  • Choroidal circulation
  • Hyperthermia
  • Retinal circulation

ASJC Scopus subject areas

  • Human Factors and Ergonomics
  • Physiology
  • Orthopedics and Sports Medicine
  • Anthropology
  • Public Health, Environmental and Occupational Health
  • Physiology (medical)


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