Phenylephrine hydrochloride ophthalmic solution is an alpha-1 adrenergic receptor agonist commonly used topically for dilation prior to ocular fundus examination. In the eye, phenylephrine acts locally as a potent vasoconstrictor and mydriatic by constricting ophthalmic blood vessels and the radial dilator muscle of the iris. Episcleral venous pressure (EVP) is a determinant of intraocular pressure (IOP) and can be measured non-invasively by venomanometry. Since phenylephrine is a vasoconstrictor, it may affect episcleral venous tone, but the effect on EVP is unknown. Understanding the physiology of episcleral veins helps us in better understanding of pathophysiology of glaucoma.

Inclusion Criteria:

• Any self-declared ethno-racial category.
• Medically healthy subjects.
• Subjects with two healthy eyes.
• Intraocular pressure (IOP) less than 22 mmHg in each eye.
• Best-corrected visual acuity (BCVA) in each eye 20/50 or better.
• Open angles in both eyes.
• Contact lens wear stopped at least 3 days prior to study, and during the study.
• Ability to cooperate for examinations required for study.

Exclusion Criteria:

• Chronic or acute ophthalmic diseases including glaucoma, wet type macular degeneration, uveitis and clinically significant cataract.
• Evidence of ocular infection, inflammation, clinically significant blepharitis or conjunctivitis.
• Cornea pathologic changes preventing reliable measurement.
• Narrow anterior chamber angle.
• Previous intraocular surgeries, laser procedures, and intravitreal injections.
• Previous corneal refractive surgeries.
• Myopia greater than -6.00 D spherical equivalent.
• Hyperopia greater than +2.00 D spherical equivalent.
• Lack of suitable episcleral vein for measurement.
• Ocular trauma within the past 6 months.
• Ocular infection or ocular inflammation in the past 3 months.
• Ocular medication of any kind within 30 days of study visit.
• Known hypersensitivity to Phenylephrine or topical anesthetic medication.
• Severe hypertension: Systolic blood pressure greater than 180 mmHg and/or diastolic blood pressure greater than 105 mmHg.
• A known history of ischemic heart disease (angina or myocardial infarction), cerebrovascular accidents, cardiac arrhythmias, cerebral or aortic aneurysms.
• Uncontrolled diabetes mellitus.
• Uncontrolled hyperthyroidism.
• Use of some systemic medications within 30 days prior to study including: β-adrenergic antagonists, α-adrenergic agonists and antagonists, calcium channel blockers, diuretics, vasodilators, monoamine oxidase inhibitors, and systemic steroids.
• Participation in any interventional study within the past 30 days prior to study visit.
• Women who are pregnant.

Adverse Events were collected for 1 year