I don't think eye problems are the reason for the headaches. As far as I know I've always had normal vision, and I haven't noticed anything being less clear than it was before.
From the three basic eye conditions which can be fixed with glasses, only two cause headaches, and only one is noticable early by perception, the one that doesn't cause headaches.
First, there's nearsighted. This one is easily recognizable, as you will notice things in a distance get less sharp. Trouble reading license plates at a distance you used to be able to before is a good early sign. This one will not cause headaches.
Then there's farsighted. This one will cause headaches, because when it's still a minor deviation, your eye muscles can correct for it. This puts a constant strain on them, causing headaches. When it gets worse it becomes noticable though, because you can't read things that you hold to close to your eyes anymore.
Third, there's astigmatism. This is caused by your eye's cornea or inner lens becoming irregulrily shaped. Will cause nasty headaches. Will become noticable through unsharp vision eventually, but causes headaches before that.
So while you say you haven't noticed anything wrong with your eyesight, there might just be a minor aspect of either farsightedness or astigmatism setting in, causing headaches.
But yeah, it could just as well be stress. Can't hurt to have your eyes checked at an optrician though, to rule eyesight out as a culprit.
edit: NB. Farsightedness is a common trait in the aging process. Starts at around age 35-40. Hardly noticable at first, unless your hobby is admiring paintings on rice grains. It can slow down, or even slightly reverse nearsightedness. It's not uncommon for older people with dual focus glasses to see the minus factor decrease and the plus increase over the years.