Inclusion criteria:
* Adults aged Eighteen (18) years and older with a diagnosis of mild to moderate open-angle glaucoma (OAG), currently on an on-label use of combination topical medication of Cosopt and Latanoprost for a minimum of 1 month. Evidence of optic nerve damage will be based on AAO Preferred Practice Patterns guidelines using either or both of the following:
* Optic disc or retinal nerve fiber layer (RNFL) structural abnormalities
* Diffuse or focal narrowing, or notching, of the optic disc rim, especially at the inferior or superior poles, which forms the basis for the ISNT rule
* Progressive narrowing of the neuroretinal rim with an associated increase in cupping of the optic disc
* Diffuse or localized abnormalities of the parapapillary RNFL, especially at the inferior or superior poles
* Disc rim, parapapillary RNFL, or lamina cribrosa hemorrhages
* Optic disc neural rim asymmetry of the two eyes consistent with loss of neural tissue
* Large extent of parapapillary atrophy
* Reliable and reproducible visual field abnormality considered a valid representation of the subject's functional status
* Visual field damage consistent with RNFL damage (e.g. nasal step, arcuate field defect, or paracentral depression in clusters of test sites)
* Visual field loss across the horizontal midline in one hemifield that exceeds loss in the opposite hemifield (in early/ moderate cases)
* Absence of other known explanations (e.g. optic disc drusen, optic nerve pit)
* Mean diurnal IOP ≥ 18 mmHg and \< 28 mmHg at baseline in at least one eye with an inter-eye IOP difference \< 5 mmHg.
* A central corneal thickness (CCT) within the range of 450-650 µm
Exclusion criteria:
* Patients with prior ocular procedures or intraocular surgery within 1 year prior to baseline (e.g. cataract surgery).
* Patients with prior history of glaucoma surgeries or laser treatment except patients with history of SLT \>1 yr prior to baseline.
* Contraindications or known hypersensitivity to any or all the study medications including Rocklatan, Simbrinza, Cosopt and Latanoprost or related class of drugs.
* Patients with known history or presence of uncontrolled systemic diseases including diseases that, in investigator's opinion, may make it unsafe or undesirable for the subject to participate in the study and/ or limit adherence.
* Patients with known history or presence of significant ocular diseases including corneal diseases, dystrophies or abnormalities that would prevent accurate IOP readings with GAT.
* Patients with a history of uncontrolled IOP with the combination of either Rocklatan + Simbrinza or Cosopt + Latanoprost dual therapy.
* Significant ocular surface findings (e.g. hyperemia, irritation) found during slit lamp examination that might affect the study.
* Chronic use of any systemic medication for chronic diseases that may affect IOP.
* Subjects who are pregnant, lactating or planning a pregnancy.
* Any condition in the opinion in the investigator that would potentially confound the results of this study
