I have them on my face for hours at a time in very bright light as I work mostly outside as an engineer for the state. They are very comfortable, cut the glare really well after extended use. I don't get a headache/eye ache. When I wore the cheaper brands, I found I would get an eye ache or head ache after a while. It took me a while to realize that their lenses were not cut properly and caused subtle adjustments by my eye to focus and the aches came from eyestrain. Not with these.