Effects of Netarsudil and Timolol on Retinal Blood Vessel Density and Visual Acuity

Inclusion Criteria: * Subjects must be between 40 to 90 years of age, inclusive, on the date the Informed Consent Form (ICF) is signed and with the capacity to provide voluntary informed consent * Subjects must be able to read, understand, and provide written informed consent on the Institutional Review Board (IRB) approved ICF * Subjects who are able and willing to comply with all treatment and follow-up/study procedures * Female subjects who are not of childbearing potential or female subjects who have a negative urine pregnancy test result at Visit 1 (Screening) and Visit 3 (Randomization, Week 1) * Females of childbearing potential, defined as a female who is fertile following menarche, must have a negative serum pregnancy test at screening and agree to use an acceptable method of contraception throughout their participation in the study. Note: Female subjects who have been surgically sterilized (e.g., hysterectomy or bilateral tubal ligation) or who are postmenopausal (defined as total cessation of menses for \> 1 year) will not be considered "female subjects of childbearing potential". Exclusion Criteria: * Subjects must have a diagnosis of OAG (including pigmentary or pseudoexfoliative) or OHT in 1 or both eyes. Subjects must not have ocular diseases to be included in the normal group. * Subjects must have a diagnosis of OAG (including pigmentary or pseudoexfoliative) or OHT in 1 or both eyes. Subjects must not have ocular diseases to be included in the normal group. * Subjects who are treatment-naïve must meet the following Intraocular Pressure (IOP) requirements at Visit 1 (Screening), and pretreated subjects must meet the following IOP requirements at Visit 2 (End of Washout):Intraocular pressure ≥ 20 mmHg in at least 1 eye and ≤ 30 mmHg in both eyes. * Subjects participating in any drug or device clinical investigation within 30 days prior to Visit 1 (Screening) for subjects requiring a washout period, or 30 days prior to Visit 3 (Randomization, Week 1) for treatment naïve subjects. * Subjects who anticipate participating in any other drug or device clinical investigation within the duration of this study. * Subjects with a history or presence of chronic generalized systemic disease that the Investigator feels might increase the risk to the subject or confound the results of the study. * Female subjects who are pregnant or breastfeeding. * Subjects currently taking systemic B-adrenergic antagonists. * Subjects with an anticipated need to initiate or modify medication (systemic or topical) that is known to affect IOP (eg, α-adrenergic agonists, calcium channel blockers, Angiotensin Converting Enzyme \[ACE\] inhibitors, and angiotensin II receptor blockers). * Subjects with known hypersensitivity or contraindications to netarsudil or any of the ingredients in the study drugs. * Subjects with known hypersensitivity or contraindications to timolol maleate or other adrenergic receptor antagonists or any of the ingredients in the study drugs. * Subjects who are expected to require treatment with ocular or systemic corticosteroids. * Subjects who are in need of any other topical or systemic treatment of OAG or OHT. * Subjects who are unable to discontinue contact lens use during and for 15 minutes following instillation of study drug and for 24 hours before check-in to and during each study visit. * Subjects with a central corneal thickness greater than 600 um in either eye. * Subjects with any condition that prevents reliable applanation tonometry (eg, significant corneal surface abnormalities) in either eye. * Subjects with advanced glaucoma. * Subjects with any condition that prevents clear visualization of the fundus in either eye. * Subjects who are monocular. * Subjects with previous or active corneal disease in either eye. * Subjects with current or a history of severe dry eye in either eye. * Subjects with active optic disc hemorrhage in either eye. * Subjects with current or a history of central/branch retinal vein or artery occlusion in either eye. * Subjects with current or a history of macular edema in either eye. * Subjects with very narrow angles (3 quadrants with less than Grade 2 according to Shaffer's anterior chamber angle grading system) and subjects with angle closure, congenital, and secondary glaucoma, and subjects with history of angle closure in either eye. * Subjects with a diagnosis of a clinically significant or progressive retinal disease (eg, diabetic retinopathy, macular degeneration) in either eye. * Subjects with any intraocular infection or inflammation in either eye within 3 months prior to Visit 1 (Screening). * Subjects with a history of ocular laser surgery in either eye within the 3 months prior to Visit 1 (Screening). * Subjects with a history of incisional ocular surgery or severe trauma in either eye within 3 months prior to Visit 1 (Screening).