Hello Dry eyes and raised pressure are two separate issues. However brow ache can be linked to the raised pressure. A pressure of 21 doesnt really signify anything in itself. That too just one reading. The nerve condition, corneal thickness Visual Fields and OCT etc  are few other parameters which need to be looked at before commenting on anything. There are people for whom pressure of 21 is normal also. So don't worry.

Hello IOP of 21 mm hg is just a risk factor for glaucoma We need additional information like central corneal thickness, optic nerve head condition,visual field etc Kindly share your case file and test reports so that I may guide you better