Squatting for a long time stood up giddy eye black, what reason is this

Squatting for a long time to stand up dizzy eyes black, considered to be related to orthostatic hypotension, squatting for a long time when the position suddenly changes, will lead to lower limb blood flow can not be timely supplied to the brain, resulting in transient blood supply to the brain, resulting in dizziness eyes black; long squatting after the rise speed should be slow, not too fast.