Dorzolamide+Timolol Multidose Preservative-free vs Dorzolamida+Timolol BAK Preserved Efficacy and Safety

Inclusion Criteria: * Older than 18 years old * Patients with POAG and OH * PIO \< 20 mmHg * Under treatment with Dorzolamide + Timolol BAK preserved at least 6 month after * OSDI \> 13 \& one of these ocular signs (BUT \<6sec or Schirmer test \< 5 mm/5min or corneal staining positive) * Corneal thickness between 520-580 um. Exclusion Criteria: * Patient with severe respiratory diseases (asthma, COPD and other bronchospactic diseases). * Patient with cardiovascular diseases (Sinus Bradycardia, AV Block, Cardiac Failure, Cardiogenic Shock). * Severe renal impairment (CrCl \<30 mL/min) * Progressive diseases of the retina other than glaucoma * Inflammation and/or infecctions active * Ocular surface syndrome other than Ocular Surface disease * Eyelid disorder * Systemic adminsitration of Betablockers or carbonic anhydrase inhibitors * Patient that requires another antigluacomatous eye drop other than fixed combination of Dorzolamide/Timolol * Patients who use regularly lubricant eye drops * Patient who use regularly contact lenses * Patient with autoinmune diseases * Patients who underwent kerato-refractive laser procedures, cornea or corneal surface surgery, including, but not limited to, LASIK and PRK, within 6 months prior to the baseline visit. * Patients who have undergone a laser procedure or intraocular surgery or extraocular in either eye within 6 months prior to the baseline visit. * Patients with severe central visual field loss in either eye based onclinical judgment of the investigator. For the Humphrey and Octopus perimeters, the severe loss The visual field is defined as a sensitivity less than or equal to 10 dB in at least two(2) of the four (4) visual field test points closest to the fixation point * Patients with known hypersensitivity to any of the components of bothdrugs under study. * Pregnant or lactating women. * Women of childbearing age who are not using a contraceptive method.