Glare, Snow Blindness, and Photophobia Outdoors
Outdoor glare headache is caused by luminance contrast, not by total brightness, and that distinction decides what actually helps. A uniformly bright overcast sky and a low winter sun glinting off wet tarmac can measure similar overall light levels while producing completely different amounts of discomfort, because glare is what happens when one part of your visual field is dramatically brighter than the part your eye is adapted to. Snow, water, wet roads and glass are the main culprits, and all four are worst when the sun sits low. The practical responses are polarisation for reflected glare, a brimmed hat for sky glare, tinted lenses in the FL-41 range for the specific wavelengths that drive migraine photophobia, and — importantly — avoiding dark sunglasses indoors, which makes light sensitivity worse over time rather than better.
Snow blindness is a separate injury with a separate mechanism, and it is worth understanding on its own terms.