Changes in Retinal Vasculature Phenotype and Choroidal Blood Flow at High Altitude in Healthy Lowlanders

TY - JOUR

T1 - Changes in Retinal Vasculature Phenotype and Choroidal Blood Flow at High Altitude in Healthy Lowlanders

AU - de Abreu, Jeremy

AU - Paillisser, Aymeric

AU - Berquet, Florence

AU - Hogg, Stephen

AU - Trucco, Manuel

AU - Geiser, Martial

AU - Pichon, Aurelien

AU - Furian, Michael

AU - Stauffer, Emeric

AU - Champigneulle, Benoit

AU - Brugniaux, Julien Vincent

AU - MacGillivray, Tom

AU - Verges, Samuel

AU - Chiquet, Christophe

N1 - Copyright 2025 The Authors

PY - 2025/6/16

Y1 - 2025/6/16

N2 - 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, and blood volume = ChVol) were carried out at 200 m and after 9 days at 5100 m in 11 healthy participants. Fundus images were analyzed with the semi-automatic software Vessel Assessment and Measurement Platform for Images of the Retina (VAMPIRE) version 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 concentrations were also measured at both altitudes. RESULTS. Corneal thickness increased slightly at altitude (median = 536 μm, interquartile range = 25–75%: [521–571] at 200 m vs. 561 μm [540–574] at 5100 m, P = 0.004). No participant was affected by high-altitude retinopathy. From 200 m to 5100 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), and 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). CONCLUSIONS. 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.

AB - 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, and blood volume = ChVol) were carried out at 200 m and after 9 days at 5100 m in 11 healthy participants. Fundus images were analyzed with the semi-automatic software Vessel Assessment and Measurement Platform for Images of the Retina (VAMPIRE) version 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 concentrations were also measured at both altitudes. RESULTS. Corneal thickness increased slightly at altitude (median = 536 μm, interquartile range = 25–75%: [521–571] at 200 m vs. 561 μm [540–574] at 5100 m, P = 0.004). No participant was affected by high-altitude retinopathy. From 200 m to 5100 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), and 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). CONCLUSIONS. 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.

KW - high-altitude

KW - hypoxia

KW - retinal vessels

KW - choroidal blood flow

KW - laser Doppler flowmetry

KW - VAMPIRE software

KW - central retinal artery equivalent

KW - central retinal vein equivalent

KW - retinal vessel tortuosity

KW - laser Doppler flowmetry (LDF)

KW - central retinal artery equivalent (CRAE)

KW - central retinal vein equivalent (CRVE)

KW - choroidal blood flow (ChBF)

U2 - 10.1167/iovs.66.6.50

DO - 10.1167/iovs.66.6.50

M3 - Article

C2 - 40521978

SN - 0146-0404

VL - 66

JO - Investigative Ophthalmology & Visual Science

JF - Investigative Ophthalmology & Visual Science

IS - 6

M1 - 50

ER -