I wear contacts while running and experience dry eyes and itchiness occasionally. Contacts today, though, are very gas-permeable and transfer gasses to and from the eyes much better than even 5 or 10 years ago. You might even find that not having glasses sliding down your nose enhances your running/cycling, and that you'll be able to focus on your run/ride more instead of trying to keep your glasses on your face! Good luck with whatever you choose!