Study on Micro-invasive Glaucoma Surgical (MIGS) Devices

* Data will be collected for 5 years after surgery, and the data collected will be the routine examination findings and investigations before and after surgery (as part of standard medical treatment) * Visual acuity testing, refraction, humphrey perimetry, heidelberg retinal tomography, anterior segment optical coherence tomography, pre-operative endothelial cell count, corneal pachymetry, intraocular pressure measurement, number of glaucoma medications * A log will be used to keep track of subject's wishes on the return for incidental findings (IF) according to subject's choice during the signing of consent form (however, we do not anticipate any incidental findings related to the study as this is an observational and non-interventional study). * In case of return incidental finding for subject who consented, PI will inform the research subject, or his legally authorised representatives, information and feedback on IFs. * PI with sufficient time for explanation and for the research subject to ask questions. * Sufficient information will be provided to the research subject or his legally authorised representative so that he can make an informed decision as to whether to return to the Institution for medical consultation, seek an opinion elsewhere, or to have no follow-up action with regards to the IF. Sample size and power calculations are not applicable as this observational study involves Medical Records Review and is not an interventional study.The recruitment target of 500 is based on the upper limit of the estimated number of patients who will undergo micro-invasive glaucoma surgical device implantation during the study period, though it is likely to be an overestimation. Pre-operative intraocular pressure and number of glaucoma medications will be compared with post-operative intraocular pressure and number of glaucoma medications at one year, 2 years, 3 years, 4 years and 5 years after surgery, using the paired t-test. Statistical significance is set at p\<0.05 All activities involving the patient will be performed as part of the routine diagnostic or standard medical treatment as part of the subject's standard care. This is an observational study and no activities outside standard care will be performed as part of this study.The activities not involving the patient includes screening, data collection, data analysis.