I noticed that when I am doing a hard work effort during an XC race, like attacking a punchy climb, I feel like I was blinded by a flash of light. I can see perfectly, but I have an urge to close my eyes, which I sometimes do to relax my vision after an especially hard effort. Do you have this experience? What could the reason be?
Lack of oxygen to the brain, I would guess. You should maybe talk to a doctor. If this happened like once then Id write it off as an anomaly. If it is reoccurring like it sounds, you might want to get some advice from a MD