Primary open angle glaucoma (POAG) is associated with inadequate drainage of the aqueous humor via the trabecular meshwork through the Schlemm's canal towards the systemic circulation. This may lead to an increase in IOP and may damage the optic nerve. The purpose of glaucoma management is to lower IOP in order to prevent progression of the optic neuropathy and subsequent visual loss. Firstline treatment usually includes IOP-lowering drug therapy. However, if IOP remains uncontrolled and/or the optic nerve damage progresses despite controlled IOP, surgery may be indicated. Deep sclerectomy (DS) is a non-penetrating surgical procedure for the treatment of open angle glaucoma that allows the enhancement of the aqueous outflow by removing part of the inner wall of Schlemm's canal and trabecular meshwork. DS was shown to achieve a good control on IOP over the long term.

The purpose of this study is to assess the 24-hour IOP fluctuation profile recorded with Triggerfish in patients with POAG before and after DS.

Inclusion Criteria:

• Diagnosis of POAG
• Documented glaucomatous VF damage with mean defect (MD) > 3 dB
• Progressing glaucomatous damage justifying a DS
• Aged ≥18 years, of either sex
• Not more than 4 diopters spherical equivalent on the study eye
• Not more than 2 diopters cylinder equivalent on the study eye
• Have given written informed consent, prior to any investigational procedures

Exclusion Criteria:

• Corneal or conjunctival abnormality precluding contact lens adaptation
• Severe dry eye syndrome
• 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 other clinical research within the last 4 weeks
• Any other contra-indication listed in the Triggerfish user manual