Abstract
Purpose: The aim of this study was to characterize changes in retinal vessel diameters and choroidal blood flow in healthy lowlanders during a high-altitude expedition.
Methods: Ocular examination, fundus images acquired using a handheld camera and laser Doppler flowmetry (LDF) measurements within the subfoveal choroid (blood flow: ChBF, blood velocity: ChVel, blood volume: ChVol) were carried out at 200 m and after 9 days at 5,100 m in 11 healthy participants. Fundus images were analyzed with the semi-automatic software VAMPIRE 3.2 to quantify retinal vessel parameters: the central retinal artery equivalent (CRAE), the central retinal vein equivalent (CRVE), and arterial and venular tortuosity. Hematocrit and hemoglobin concentration were also measured at both altitudes.
Results: Corneal thickness increased slightly at altitude (median: 536 μm, Interquartile 25-75%: [521-571] at 200 m vs 561 μm [540-574] at 5,100 m, p=0.004). No participant was affected by high-altitude retinopathy. From 200 m to 5,100 m, ChVol and ChBF decreased significantly (-31% [43-22], p=0.003 and -13% [22-8], p=0.01, respectively), ChVel increased (+17% [10-44], p=0.003), CRVE (+10% [3- 14], p=0.04) and venular tortuosity (+142% [71-168], p=0.04) increased significantly. The altitude-induced increase in hematocrit correlated negatively with the decrease in ChBF (r=-0.88, p<0.001) and positively with the increase in CRVE (r=0.88, p=0.01).
Conclusion: Acute high-altitude exposure leads to a decrease of ChBF (partly related to a decrease in blood volume) and an increase in retinal vein diameter and tortuosity. The physiological consequences of these changes on retinal blood flow and retinal function remain to be explored.
Methods: Ocular examination, fundus images acquired using a handheld camera and laser Doppler flowmetry (LDF) measurements within the subfoveal choroid (blood flow: ChBF, blood velocity: ChVel, blood volume: ChVol) were carried out at 200 m and after 9 days at 5,100 m in 11 healthy participants. Fundus images were analyzed with the semi-automatic software VAMPIRE 3.2 to quantify retinal vessel parameters: the central retinal artery equivalent (CRAE), the central retinal vein equivalent (CRVE), and arterial and venular tortuosity. Hematocrit and hemoglobin concentration were also measured at both altitudes.
Results: Corneal thickness increased slightly at altitude (median: 536 μm, Interquartile 25-75%: [521-571] at 200 m vs 561 μm [540-574] at 5,100 m, p=0.004). No participant was affected by high-altitude retinopathy. From 200 m to 5,100 m, ChVol and ChBF decreased significantly (-31% [43-22], p=0.003 and -13% [22-8], p=0.01, respectively), ChVel increased (+17% [10-44], p=0.003), CRVE (+10% [3- 14], p=0.04) and venular tortuosity (+142% [71-168], p=0.04) increased significantly. The altitude-induced increase in hematocrit correlated negatively with the decrease in ChBF (r=-0.88, p<0.001) and positively with the increase in CRVE (r=0.88, p=0.01).
Conclusion: Acute high-altitude exposure leads to a decrease of ChBF (partly related to a decrease in blood volume) and an increase in retinal vein diameter and tortuosity. The physiological consequences of these changes on retinal blood flow and retinal function remain to be explored.
| Original language | English |
|---|---|
| Number of pages | 8 |
| Journal | Investigative Ophthalmology & Visual Science |
| DOIs | |
| Publication status | Published - 16 Jun 2025 |
Keywords
- high-altitude
- hypoxia
- retinal vessels
- choroidal blood flow
- laser Doppler flowmetry
- VAMPIRE software
- central retinal artery equivalent
- central retinal vein equivalent
- retinal vessel tortuosity