十万个为什么·科学阅读30篇（4）

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为什么突然站起时眼前会冒金星？

Those quick flashes of light are called phosphenes, and they result from temporary drops in blood pressure.
When you stand suddenly, gravity pulls blood downward faster than your heart can pump it upward.
This causes brief under-perfusion of the retina—the light-sensitive layer at the back of your eye.
Without enough oxygen, retinal cells misfire, sending false signals that your brain interprets as light.
The effect usually lasts only a few seconds and disappears once circulation stabilizes.
Younger people experience it less often because their autonomic nervous system responds more quickly.
Dehydration, low iron, or standing after lying down for hours increases the chance of seeing phosphenes.
Unlike migraines or eye disease, this type of phosphene is harmless and requires no treatment.
Athletes sometimes use controlled versions of this effect during training to improve vascular responsiveness.
If dizziness or vision loss lasts longer than ten seconds, it’s wise to consult a healthcare provider.