High‑Altitude Living Leaves Eye Vessels Struggling

A team of researchers visited a remote town in Peru where people live at 5,100 m above sea level. They wanted to see how the thin air affects the tiny blood vessels inside the eye. The study measured vessel widths and how the vessels react when carbon dioxide levels rise.

Most of the participants (61%) had a very high count of red blood cells, a condition often called EE. Those with EE showed noticeably larger retinal veins than the others. No major differences appeared in artery size or how twisted the vessels were. At rest, the size of the veins was linked to blood thickness, haemoglobin level, total blood volume, and the pressure of carbon dioxide in the arteries.

When the researchers increased CO2 levels, retinal veins generally got a bit smaller, dropping about 9 µm on average. This change occurred for both EE and non‑EE individuals, and it was opposite to what normally happens in people living at lower altitudes. No changes were seen in artery size, vessel twist, or choroidal blood flow. The results suggest that long‑term exposure to very low oxygen can cause retinal blood vessels to malfunction.

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