- Established diagnosis of untreated or medically treated normal tension glaucoma irrespective of blood pressure level. Those currently treated with topical drops will only be included in the study if they accept to stop their medication according to the following plan: 1) Those treated with Alphagan, Combigan or Cosopt (or Trusopt, Azopt, Diamox, Neptazane) will be asked to stop their medication for a week, do the study for 24 hours, and then resume with their medication. 2) Those treated with Timolol or Xalatan (or Travatan, Lumigan) will be asked to stop their drops for one month, do the study for 24 hours, and then resume the medication regimen. The reason for this is that the study aims at investigating the relationship between blood pressure and intraocular pressure in untreated patients either for glaucoma or high blood pressure. The difference in duration of time during which patients will be off their glaucoma medication depends on the time it takes to clear the drug in the system. In both cases, glaucoma medication will be stopped from the day following the screening visit.