I was nervous riding this in June because I'd heard that it was so intense and people were greying and blacking out with some enthusiasts hating it because it was "too" intense but it was actually fine. My vision went a bit dotty but it was minor enough that I couldn't really tell whether it was legit (I was waiting for it/expecting it) or just the wind making my eyes watery. I think maybe there were some small dark spots??
Anyway, it was fine to reride multiple times including in the front and back for me. I've felt stronger g for shorter periods but it does certainly sustain it for a longer time that most rides so I can see why it divides opinion and affects eyeballs to varying degrees1