Ophthalmolgy: I have read several articles on this subject- whether using one eye as a control is helpful when starting a glaucoma drop, or just put in both eyes. The issue was whether the two eyes really behave the same way, whether fluctation in IOP would make the comparison invalid, etc. I thought it was settled- it didn’t work. Just put in both eyes. Researchers now state that with prostaglandins, it does work. Go figure.