What are dry eyes and can they be treated without medicines?

Dry eyes: Xerostomia can be treated with eye drops, as long as you find the cause (ex. Medicines that cause dryness).

Dry eye: Your description sounds like dry eye. Initial treatment is frequent artificial tears during the day, ointment at night, warm compresses a few times a day, and omega-3 fatty acid supplements. If no improvement, you should see an eye doctor for further evaluation.