Intraocular Pressure (IOP) Patterns in Fast Versus Slow Visual Field (VF) Progression Patients

Inclusion Criteria: * Age between 40 and 89 years old * Diagnosis of treated POAG (including normal tension glaucoma (NTG)) * All IOP measurements during the VF period (to be described further) equal or lower than 18 mmHg and/or on average equal or lower than 16 mmHg in the same period * Documented glaucomatous VF damage at baseline, characterized by glaucoma hemifield test result outside normal limits on at least 2 consecutive VF tests or the presence of at least 3 contiguous test points within the same hemifield on the pattern deviation plot at p\<0.01, with at least 1 point at p \< 0.005 * At least 8 visual field tests carried out within at least 2 years, all with fixation losses and false positive/negative results equal or less than 33% * For fast progressing eyes, 1) pointwise progression defined as two or more adjacent VF test locations in the same hemifield that show a threshold sensitivity rate of change more negative than -1.0 dB/year with p\<0.01 or 2) a global rate of VF change based on mean deviation (MD) more negative than -1.0 dB/year * For slowly or minimally progressing eyes a VF MD rate of change more positive than -0.5 dB/year with no significant pointwise progression as described above * Not more than 6 diopters spherical equivalent on the study eye * Have given written informed consent, prior to any investigational procedures Exclusion Criteria: * Baseline VF MD more negative than -15 dB. The rationale here is that in severely damaged visual fields, one may not be able to detect and measure rates of progression due to a 'floor effect' * Corneal or conjunctival abnormality precluding contact lens adaptation * Severe dry eye syndrome or other ocular disease * Patients with angle closure glaucoma, traumatic glaucoma or uveitic glaucoma * Patients with previous intraocular surgery in the enrolled eye, including cataract surgery * Patients with allergy to corneal anesthetic * Patients with contraindications for silicone contact lens wear * Patients not able to understand the character and individual consequences of the investigation * Participation in unrelated clinical research within the last 4 weeks