Waht causes halos around the eyes?

High cholesterol: If this is something you are seeing on the iris when you look in the mirror, it could be a sign of older age or if you are younger, high cholesterol. See your medical doctor to check your cholesterol level.

Depends: I'm assuming you mean halos around objects in your vision, like lights. Halos occur when any of the light rays entering your eye get scattered on their path to the retina (the seeing part of the eye). This could occur with dirty/scratched/outdated rx glasses, corneal irregularities (e.g., dry eye, allergies), cataract, floaters, and some macular disorders. An eye md (ophthalmologist) can help.