I've had this for years (not because of medication) - one thing that can cause it is not how
often you blink, but
how you blink. When I used to wear contact lenses (the old hard kind) I got into a habit of "flick-blinking", where the lid doesn't come down quite all the way, because full blinking was a bit uncomfortable. Then the eye can dry up more easily. And make-up can encourage this if the eye feels a little uncomfortable and doesn't somehow want to blink properly. So it's worth doing a few full blinks every so often to get the eyes into the habit. I find when I'm blinking properly, my eyesight is clearer too

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Also make sure you drink plenty of water, and not plenty of tea/coffee/alcohol, as hydration is a good thing.