Effect of topical phenylephrine 2.5% on episcleral venous pressure in normal human eyes

Arash Kazemi, Jay W. McLaren, Arthur J. Sit

Research output: Contribution to journalArticlepeer-review


PURPOSE. Phenylephrine has been shown to affect intraocular pressure (IOP) but the mechanism of action is poorly understood. However, its action as a vasoconstrictor suggests possible effects on episcleral venous pressure (EVP). In this study, we evaluated the effect of phenylephrine on EVP and IOP in healthy subjects. METHODS. Forty eyes of 20 subjects were included. Each subject received 3 drops of phenylephrine 2.5% in one eye at 1-minute intervals. The fellow eye served as control. Blood pressure, heart rate, and IOP and EVP of both eyes were measured at baseline, 15 minutes, and 60 minutes after instillation of phenylephrine. IOP was measured by pneumatonometry. EVP was assessed by using a computer-controlled episcleral venomanometer. Changes in IOP, EVP, blood pressure, and heart rate at 15 and 60 minutes were analyzed by paired t-tests. RESULTS. IOP increased 15 minutes after instillation of phenylephrine in both treated (P = 0.001) and control eyes (P = 0.01) and returned to baseline at 60 minutes. The change in IOP at 15 minutes was not significantly different between the 2 groups. EVP in treated eyes was unchanged at 15 minutes (P = 0.8) but decreased significantly at 60 minutes (P < 0.001). In control eyes, there was no change in EVP at any time (P > 0.6). There were no significant changes from baseline in systolic and diastolic blood pressure and heart rate after instillation of phenylephrine. CONCLUSIONS. IOP elevation associated with topical phenylephrine is not caused by an increase in EVP in healthy subjects. Instead, EVP decreases with phenylephrine, but the mechanism remains to be determined.

Original languageEnglish (US)
Article number4
JournalInvestigative Ophthalmology and Visual Science
Issue number13
StatePublished - Oct 2021


  • Episcleral venous pressure
  • Intraocular pressure
  • Phenylephrine
  • Vasoconstriction

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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