Skip to content
How It Works
Explore
Ask a Question Resources Pricing
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 19 peer-reviewed journal articles Updated
Ophthalmology

Identifying the Root Cause of Your High Eye Pressure

At a Glance

Glaucoma with elevated episcleral venous pressure occurs when pressure in the veins around the eye blocks normal fluid drainage. Doctors look for causes such as a carotid-cavernous fistula, thyroid eye disease, tumors, or systemic vascular blockage before calling it idiopathic.

When you are told your eye pressure is high because of elevated episcleral venous pressure (EVP), the most important question is not just “how do we lower the pressure?” but “why is the pressure high in the first place?” [1][2].

In this condition, the high eye pressure is often a symptom of a backup further down the drainage line. Identifying the source of that backup is critical because many of the underlying causes require specific treatment, and treating the cause can improve the eye pressure, although IOP may remain elevated and established optic-nerve damage does not reverse [3][4].

Vascular Shunts: The Carotid-Cavernous Fistula

The most common “mechanical” cause of elevated EVP is a carotid-cavernous fistula (CCF). This is an abnormal connection between an artery (high pressure) and a vein (low pressure) behind the eye [5].

  • How it works: High-pressure arterial blood “shorts out” into the venous system, causing the veins to engorge and the pressure to back up into the eye [6].
  • Direct CCF: Usually caused by a head injury or accident. These are high-flow and often cause sudden bulging of the eye, severe redness, and a pulsing sound in the ear (bruit) [7][5].
  • Indirect CCF: These are lower-flow and can happen spontaneously, especially in older adults or those with high blood pressure. They may be subtle, causing only mild redness or slightly high eye pressure that is easily mistaken for standard glaucoma [7][8].

Congenital Causes: Sturge-Weber Syndrome

Sturge-Weber Syndrome is a condition present from birth that is often identified by a “port-wine stain” birthmark on the face [9]. In these patients, abnormal blood vessels within the eye and the eye socket increase the “floor” of the eye pressure (EVP). This can cause glaucoma either at birth or later in childhood or adulthood [10].

Orbital and Systemic Obstructions

Sometimes the veins aren’t over-pressurized by a leak (like a fistula), but are instead being squeezed or blocked:

  • Thyroid Eye Disease (TED): Swelling of the muscles and fat behind the eye can compress the veins that drain fluid away, leading to a pressure backup [11].
  • Orbital Tumors: Any mass in the eye socket can physically press on the drainage veins [3].
  • Systemic Issues: Conditions that increase pressure in the chest or head—such as severe pulmonary hypertension or superior vena cava syndrome—can prevent blood from flowing easily out of the head, causing a backup all the way to the eye [12][13].

Why “Idiopathic” is the Last Step

If your doctor uses the term Idiopathic Elevated EVP (also known as Radius-Maumenee Syndrome), it means they have performed an investigation based on your clinical signs and found no secondary cause like a fistula or tumor [2].

This is known as a diagnosis of exclusion. Because some causes (like low-flow fistulas) can be very hard to see on standard scans, your medical team evaluates testing options carefully before deciding the condition is idiopathic [14][2].

The Importance of Proper Workup

Treating the eye pressure may need to continue while the cause is being assessed. Workup is individualized according to your symptoms, whether one or both eyes are affected, and examination findings. For example, if a fistula is the cause, certain glaucoma surgeries can be riskier due to the high venous pressure [15][16].

A standard workup often includes:

  1. Clinical Exam: Looking for “corkscrew” vessels on the eye or blood in the drainage canal [5][17].
  2. Imaging: An MRI or CT scan of the orbits (eye sockets) and brain to look for swollen veins or tumors [14][18].
  3. Vascular Scans: An MRA or CTA to look at blood flow. If a low-flow fistula is still suspected but not seen, a digital subtraction angiography (DSA) may be considered. DSA is an invasive specialist test with specific neurologic and vascular risks, and is used when the expected benefit (such as treatment planning) justifies those risks [8][19].

By identifying and addressing the underlying cause, doctors can often lower the eye pressure more effectively [6][4].

Common questions in this guide

Why does elevated episcleral venous pressure cause glaucoma?
Pressure in the veins around the eye can slow the normal drainage of fluid from the eye, raising pressure inside the eye. The high pressure may come from an abnormal blood-vessel connection, a blockage around or beyond the eye, a congenital condition, or an unidentified cause.
Could a carotid-cavernous fistula be behind my high eye pressure?
Yes. A carotid-cavernous fistula is an abnormal connection between an artery and a vein behind the eye that can raise pressure in the eye's draining veins. A direct fistula may follow a head injury and cause sudden bulging and marked redness, while a low-flow fistula may cause only mild redness or pressure elevation.
What tests can find the cause of elevated eye pressure?
Doctors may examine the eye for enlarged, corkscrew-like vessels or blood in the drainage canal and use MRI or CT scans of the eye sockets and brain. MRA or CTA can assess blood flow. If a low-flow fistula is still suspected, digital subtraction angiography may be considered after weighing its risks and possible benefit.
What does idiopathic elevated EVP or Radius-Maumenee syndrome mean?
It means testing and clinical evaluation have not found a secondary cause, such as a fistula or tumor. It is called a diagnosis of exclusion because some low-flow fistulas are difficult to detect on standard scans.
Can treating the cause bring my eye pressure back to normal?
Treating the underlying problem can lower eye pressure more effectively, but pressure may remain high in some people. Any optic-nerve damage that is already established does not reverse, so pressure control and follow-up remain important.
Is glaucoma surgery riskier when episcleral venous pressure is high?
Some glaucoma surgeries can carry greater risk when pressure in the veins around the eye remains high. Ask your glaucoma specialist how the suspected cause, scan results, and current eye pressure affect the timing and choice of treatment.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my imaging results and symptoms, have we effectively ruled out a carotid-cavernous fistula?
  2. 2.Is my eye pressure being caused by a problem localized to the eye, or is it a symptom of a broader vascular or orbital issue?
  3. 3.What specific findings on my MRI or MRA led us to the current diagnosis?
  4. 4.If my condition is related to thyroid eye disease or another systemic issue, should I be seeing a specialist (like an endocrinologist or neuro-ophthalmologist) to manage the underlying cause?
  5. 5.What are the risks of performing glaucoma surgery if my venous pressure remains high?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (19)
  1. 1

    [Glaucoma due to elevated episcleral venous pressure].

    Greslechner R, Oberacher-Velten I

    Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft 2019; (116(5)):423-429 doi:10.1007/s00347-018-0828-4.

    PMID: 30506098
  2. 2

    [Radius-Maumenee syndrome: A rare cause of glaucoma].

    Bouaziz K, Aragno V, Batras M, et al.

    Journal francais d'ophtalmologie 2020; (43(9)):837-841 doi:10.1016/j.jfo.2020.01.024.

    PMID: 32948355
  3. 3

    Ocular Adnexal Lymphoma Presenting as Refractory Unilateral Open-angle Glaucoma.

    Sears NC, Singh A, Singh AD

    Journal of glaucoma 2016; (25(8)):e741-4 doi:10.1097/IJG.0000000000000459.

    PMID: 27300646
  4. 4

    Secondary open-angle glaucoma and serous macular detachment associated with pulmonary hypertension.

    Gupta I, Haddock L, Greenfield DS

    American journal of ophthalmology case reports 2020; (20()):100878 doi:10.1016/j.ajoc.2020.100878.

    PMID: 32875159
  5. 5

    Carotid-cavernous fistula from the perspective of an ophthalmologist A Review.

    Jozef Č

    Ceska a slovenska oftalmologie : casopis Ceske oftalmologicke spolecnosti a Slovenske oftalmologicke spolecnosti 2020; (1(Ahead of print)):1-8 doi:10.31348/2020/8.

    PMID: 33086846
  6. 6

    Intraocular Pressure in the Eyes of Patients With Carotid-Cavernous Fistulas: Profile, Intereye Asymmetry, and Treatment Outcomes.

    Khurana M, Alam MS, Balekudaru S, et al.

    Journal of glaucoma 2019; (28(12)):1074-1078 doi:10.1097/IJG.0000000000001392.

    PMID: 31658226
  7. 7

    Endovascular Modalities for the Treatment of Cavernous Sinus Arteriovenous Fistulas: A Single-Center Experience.

    Hassan T, Rashad S, Aziz W, et al.

    Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 2015; (24(12)):2824-38.

    PMID: 26409721
  8. 8

    Carotid Cavernous Sinus Fistula with Contralateral Feed Not Diagnosed by Virtual Assessment or by Non-Invasive Vascular Imaging.

    Ing E, Tyndel F, Tang J, Marotta TR

    Case reports in ophthalmology 2021; (12(2)):712-716 doi:10.1159/000518806.

    PMID: 34594209
  9. 9

    Ocular manifestations of Sturge-Weber syndrome: pathogenesis, diagnosis, and management.

    Mantelli F, Bruscolini A, La Cava M, et al.

    Clinical ophthalmology (Auckland, N.Z.) 2016; (10()):871-8 doi:10.2147/OPTH.S101963.

    PMID: 27257371
  10. 10

    Sturge-Weber syndrome secondary glaucoma: From Pathogenesis to Treatment.

    Wen T, Wang L, Luo H, Tang L

    Eye and vision (London, England) 2025; (12(1)):16 doi:10.1186/s40662-025-00432-6.

    PMID: 40241121
  11. 11

    Intraocular Pressure and Glaucoma in Thyroid Eye Disease.

    Betzler BK, Young SM, Sundar G

    Ophthalmic plastic and reconstructive surgery 2022; (38(3)):219-225 doi:10.1097/IOP.0000000000002049.

    PMID: 34406153
  12. 12

    Ocular manifestations of pulmonary hypertension.

    Lewczuk N, Zdebik A, Bogusławska J, et al.

    Survey of ophthalmology 2019; (64(5)):694-699 doi:10.1016/j.survophthal.2019.02.009.

    PMID: 30849428
  13. 13

    Ocular manifestations of a rare congenital heart defect: Advanced glaucoma and retinal vein occlusion associated with double-chambered right ventricle.

    Khoury JA, Kanda P, Gill H, et al.

    American journal of ophthalmology case reports 2026; (42()):102558 doi:10.1016/j.ajoc.2026.102558.

    PMID: 41890784
  14. 14

    Bilateral Episcleral Corkscrew Vessels: Expedition into the Unknown - Case Report.

    Madeira C, Alves G, Godinho G, et al.

    Case reports in ophthalmology 2022; (13(1)):109-115 doi:10.1159/000515971.

    PMID: 35431882
  15. 15

    RARE PRESENTATION OF BILATERAL CAROTID-CAVERNOUS FISTULA AS SUPRACHOROIDAL HEMORRHAGE DURING CATARACT SURGERY.

    Zainol N, Raman P, Devi-S P, Mohd Khalid KH

    Retinal cases & brief reports 2023; (17(4)):362-364 doi:10.1097/ICB.0000000000001186.

    PMID: 34381008
  16. 16

    Radius-Maumenee syndrome-associated glaucoma, a therapeutic challenge: A case report.

    Lavaris A, Petrushkin H, Nikita E

    European journal of ophthalmology 2024; (34(5)):NP37-NP43 doi:10.1177/11206721241261096.

    PMID: 38859765
  17. 17

    Idiopathic elevated episcleral venous pressure in a teenager.

    Sun CQ, Medert CM, Chang TC

    American journal of ophthalmology case reports 2020; (18()):100712 doi:10.1016/j.ajoc.2020.100712.

    PMID: 32322757
  18. 18

    Low-flow carotid-cavernous fistula associated with cavernous sinus thrombosis: An ophthalmic presentation.

    Moro-Muniz M, Sanz Marco E, Salom Alonso D

    Archivos de la Sociedad Espanola de Oftalmologia 2026; 502592 doi:10.1016/j.oftale.2026.502592.

    PMID: 42349550
  19. 19

    Direct Carotid Cavernous Fistulas.

    Ide S, Kiyosue H, Tokuyama K, et al.

    Journal of neuroendovascular therapy 2020; (14(12)):583-592 doi:10.5797/jnet.ra.2020-0131.

    PMID: 37502141

This page explains possible causes and testing for glaucoma with elevated episcleral venous pressure for informational purposes only; it does not constitute medical advice. Your ophthalmologist and other specialists should interpret your symptoms and scans.

Get notified when new evidence is published on glaucoma with elevated episcleral venous pressure.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.