Originally Posted by junbumkim
What you experienced is orthostatic hypotension, which has to do with our nerve system not regulating our blood pressure quickly enough in relation to our change in posture (from lying to standing). In dehydration, blood circulation can decrease because there is too much fluid loss, and this does not resolve until fluid has been replaced. And, dehydration is pretty serious if it's causing blurry vision, and there will definitely be other symptoms such as dizziness, increased heart rate, etc. And, these symptoms will not resolve until you replenish fluid. Simply, you feel thirsty until you drink water.
The OP stated the blurry vision lasted only momentarily and is caused when he goes upto the net to volley. This sounds more like his eyes not quickly adapting to the change rather than dehydration.
I know what it is. They kinda taught me physiology at the medical school here. The question is whether it can occur momentarily or how short a time period it could occur. That they didn't teach me, probably because we don't know.
I don't know what it is, but the solution is simple: stay at the baseline.