Inclusion Criteria:  Patients with primary open angle glaucoma or ocular hypertension as defined in Early Manifest Glaucoma Trial > 18 years old Signed informed consent 3 or more months under monotherapy treatment with tafluprost 0.0015%, latanoprost 0.005% with BAK 0.2mg/ml or latanoprost 0.005%. Untreated patients with ocular hypertension must be treatment naïve for the pathology. No presence or history of previous ocular diseases other than glaucoma or ocular hypertension, started before the use of hypotensive medication.  Exclusion Criteria:  Ocular surgery in the previous 6 months. Any ocular surface disease not related to inclusion criteria or related issues active within the last 6 months. Any topical treatment other than the evaluated in this study in the last 3 months. In case of artificial teardrops use, only non conservative ones are allowed, with no more than 4 times per day use, and treatment must be suspended 5 days before inclusion. Use of contact lenses in the las 4 weeks. Any mental or physical disease that may prevent performing the required tests for the study.