I mean, there's no way to stop the glands there from producing sweat. The only ideas I can offer are better ventilated sunglasses so you have more airflow over that part of your face, or maybe a small hand towel in a back pocket that you can use to dab your face every few minutes. If your back is soaked with sweat you may need a plastic baggy. I usually wear thin long finger gloves when it's really hot so my hands don't slide all over my hoods and bars, those tend to be better for wiping away eye sweat.