Yesterday, I started having cloudy vision in one eye - when I look through only that eye, about 50% of visual field is gone. What to do?

See an eye doctor. Vision is very precious and often sudden loss of vision is not a good sign. If it is back to normal, consider yourself lucky. I would recommend seeing your doc or an eye doc for an evaluation as soon as you can. Dizziness with blurry vision etc..Typically occurs on both sides, so your one-sided symptom is concerning. Consult doc asap. Good luck.
See and eye doctor. See and eye doctor immediately. The cause of your loss of vision needs to be identified as soon as possible.