So I experienced something new today while riding "Longfeng Roller Coaster" (https://rcdb.com/11346.htm). During the second loop my vision faded quite a bit which caught me by surprise. But I hear it is normal on some coasters. If anyone has experienced this please share!
I fully greyed out on Intimidator 305 earlier this year towards the back of the train, no colour in my vision at all! I've had fuzzy vision on a number of coasters including Nitro, Backlot Stunt Coaster and Nemesis.
i305, on just about every ride I did on it - although I did seem to be getting more tolerant to it towards the end of the day. There was one ride on it (which I think was my 3rd in a row without getting off) where I have no recollection from the bottom of the drop to going over the first hill!