A Study to Evaluate Variations in Episcleral Venous Pressure


About this study

The purpose of this study is to investigate the daily variations in episcleral venous pressure (EVP), the relationship between EVP and blood pressure (BP) variations, and the effect of anti-hypertension medications on these variations. The effect of blood volume increase after water drinking on BP, intraocular pressure (IOP), and EVP will also be assessed.

Participation eligibility

Participant eligibility includes age, gender, type and stage of disease, and previous treatments or health concerns. Guidelines differ from study to study, and identify who can or cannot participate. There is no guarantee that every individual who qualifies and wants to participate in a trial will be enrolled. Contact the study team to discuss study eligibility and potential participation.

Inclusion Criteria:

  • ≥ 35 years of age.
  • Either gender.
  • Any self-declared ethno-racial category.
  • Subjects with two healthy eyes with the crystalline lens, without glaucoma or any other clinically significant eye diseases.
  • Open angles in both eyes.
  • Intraocular pressure less than 24 mmHg in either eye.
  • Be able and willing to provide signed informed consent and follow study instructions.
  • Ability to cooperate for the examinations required for study and be able to attend all study visits.
  • Contact lenses removed before the study visit.
  • Best-corrected visual acuity (BCVA) in each eye of 20/50 or better.

Exclusion Criteria:

  • Female subjects who are pregnant or breastfeeding.
  • Narrow angle of < Shaffer grade 2, peripheral synechiae, or peripheral iridotomy in either eye
  • Subjects with a central corneal thickness less than 480 µm or greater than 620 µm in either eye.
  • Chronic or recurrent inflammatory eye diseases.
  • Ocular infection or ocular inflammation in the past 3 months.
  • Ocular trauma other than corneal abrasion within the past 6 months.
  • Clinically significant retinal disease (e.g., diabetic retinopathy, exudative or severe non-exudative macular degeneration).
  • Cornea pathologic changes preventing reliable measurement (e.g., scarring, opacity) in either eye.
  • Previous intraocular surgery or laser procedure in either eye.
  • Previous corneal refractive surgeries.
  • Myopia greater than -6.00D, or hyperopia greater than +2.00D.
  • Moderate to severe dry eye in either eye.
  • Serious hypersensitivity to topical anesthetic eye drops.
  • Use of any topical ophthalmic medications other than lubricants and artificial tears within the past 30 days.
  • For healthy subjects cohort: Subjects with a history or presence of chronic generalized systemic disease (such as hypertension, diabetes) that may confound the results of the study.
  • Systolic blood pressure > 145 mmHg or/and diastolic blood pressure > 95 mmHg.
  • For healthy subjects cohort: Subjects who are currently using or have a history of using medications (systemic or topical) that are known to affect IOP or blood pressure within the past 30 days (e.g., systemic/inhaled steroids, α-adrenergic agonists and antagonists, β-adrenergic antagonists, calcium channel blockers, angiotensin converting enzyme [ACE] inhibitors, and  angiotensin II receptor blockers).
  • Subjects with a history or presence of any systemic condition (e.g., heart failure or kidney disease) for which drinking the water volumes proposed in this study could be harmful (for water drinking test visit).
  • For hypertensive subjects cohort: Subjects who are currently using or have a history of using systemic/inhaled steroids within the past 30 days.
  • Use of any products of cannabis (THC or CBD compounds) within the past 30 days.
  • Lack of suitable episcleral vein for EVP measurement.
  •  Subjects who are not fully vaccinated against COVID-19.

Eligibility last updated 12/16/21. Questions regarding updates should be directed to the study team contact.


Participating Mayo Clinic locations

Study statuses change often. Please contact the study team for the most up-to-date information regarding possible participation.

Mayo Clinic Location Status Contact

Rochester, Minn.

Mayo Clinic principal investigator

Arthur Sit, M.D., M.S.

Open for enrollment

Contact information:

Bridgette Halder C.O.A.

(507) 422-2780


More information


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