Increased Episcleral Venous Pressure as an Etiology of Glaucoma
Advice on differential diagnosis and management.
Patient No. 1
A 54-year-old Asian woman presented after 1 month of redness in her right eye accompanied by swollen eyelids but minimal pain. The patient had no significant prior medical or ocular history.
On examination, her visual acuity was 20/25 OD and 20/20 OS. We noted no afferent pupillary defect. Hertel measurements demonstrated 5 mm of proptosis (Figure 1A), a slight abduction deficit, and mild periorbital edema in the right eye. IOP measured 32 mm Hg OD and 18 mm Hg OS. The slit-lamp exam showed dilated and tortuous conjunctival and episcleral vessels in the right eye (Figure 1B). The dilated fundus exam was unremarkable, and we noted no significant cup-to-disc asymmetry (cup-to-disc ratio = 0.3 OU). Gonioscopy revealed open angles in both eyes and blood in Schlemm canal of the right eye. Computed tomography (CT) of the orbits with contrast revealed a dilated superior ophthalmic vein (Figure 1C), leading us to suspect a carotid-cavernous fistula.
We started the patient on timolol in her right eye, and the IOP decreased to 22 mm Hg. She underwent cerebral angiography, which identified a right dural carotid-cavernous fistula that was treated by embolization. At postoperative month 2.5, the patient had a visual acuity of 20/20 OU. The proptosis, motility deficit, and dilated episcleral vessels had resolved. Her IOP measured 18 mm Hg OD and 13 mm Hg OS without medication.
Patient No. 2
A 61-year-old Asian man was referred to our glaucoma clinic for elevated IOP in his right eye. The patient had no history of other ocular conditions and no significant past medical history.
On exam, his visual acuity was 20/20 OU. No significant proptosis, ptosis, or chemosis was observed, and motility was normal. We noted an afferent pupillary defect in the right eye. IOP measured 27 mm Hg OD and 21 mm Hg OS. The slit-lamp and dilated funduscopic exams were remarkable for slightly dilated episcleral vessels in the right eye (Figure 2A) and a significant cup-to-disc asymmetry (0.9 OD and 0.6 OS). Gonioscopy revealed open angles in both eyes and blood in Schlemm canal of the right eye. Visual field testing found significant visual field loss in the right eye (Figure 2B), whereas the left visual field was normal and intact. Computerized tomographic angiography was unremarkable.
The patient’s right eye was treated with brimonidine and a fixed combination of dorzolamide and timolol. The IOP has since been controlled in the low teens.
BACKGROUND AND PATHOPHYSIOLOGY
Normal EVP ranges from 8 to 10 mm Hg, and for every 1 mm Hg of elevation in EVP, the mean IOP is thought to rise 1 mm Hg.1 The underlying causes of elevated EVP can be divided into three categories: (1) venous congestion, (2) arteriovenous fistulas, and (3) idiopathic (Table 1).
The most common sign of elevated EVP is dilation and increased tortuosity of the episcleral and conjunctival vessels. Depending on the underlying cause of the increased EVP, additional findings may include proptosis, chemosis, and orbital bruit (Table 2). Gonioscopy typically reveals an open angle; in some cases, Schlemm canal may contain blood, thought to be present as a result of blood reflux from the episcleral veins. The IOP is elevated, and depending on the chronicity and severity of this increase, there may be evidence of glaucomatous optic neuropathy.
It is important to identify any underlying causes of elevated EVP. Issues to explore include a history of thyroid disease, amyloidosis, superior vena cava syndrome, Sturge-Weber syndrome, or carotid-cavernous sinus fistula, a mechanism made more likely by a history of trauma. Additional diagnostic workup for these EVP elevation causes may include orbital ultrasound, CT, and/or magnetic resonance imaging to rule out intraorbital or intracranial etiologies. Cases are only considered idiopathic when no underlying etiology is identified.
Commercial instruments to measure EVP are unavailable. Accordingly, the diagnosis of glaucoma secondary to idiopathic elevated EVP is made based on clinical findings.2
Initial management should be directed at reducing IOP, followed by the treatment of any underlying cause of the elevated EVP. Consultations with oculoplastics, neurology, neurosurgery, and/or interventional radiology may be required. Because aqueous outflow is compromised, aqueous suppressants are more effective than are medications that enhance outflow for the medical management of IOP resulting from elevated EVP. Apraclonidine in particular has been shown to be effective for lowering IOP in cases of elevated EVP, because the drug causes arterial vasoconstriction, which decreases the amount of blood flow to the eye.4
If the IOP remains uncontrolled despite medical management, then surgical options are considered. Several case reports point out that trabeculectomy in these eyes can be complicated by intraoperative or postoperative uveal effusions, even at nonhypotonous IOPs.5-7 Some physicians have recommended “tight” trabeculectomies, with multiple sutures surrounding the scleral flap, to allow gradual titration of the IOP in the postoperative period.8 In one case report of an eye with idiopathic elevation of EVP, the ophthalmologist avoided the complication of postoperative uveal effusions by performing nonpenetrating filtering surgery followed by goniopuncture (a staged trabeculectomy).9 Nonpenetrating deep sclerectomies have also been attempted, resulting in fewer complications, but they have been less successful at maintaining long-term IOP control.10 Before intervening surgically, it is important to make the patient aware of the guarded prognosis.
1. Allingham RR, Damji KF, Shields MB. Shields Textbook of Glaucoma. 6th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011.
2. Phelps CD, Armaly MF. Measurement of episcleral venous pressure. Am J Ophthalmol. 1978;85(1):35-42.
3. Foroozan R, Buono LM, Savino PJ, Sergott RC. Idiopathic dilated episcleral veins and increased intraocular pressure. Br J Ophthalmol. 2003;87(5):652-654.
4. Mantzioros N, Weinreb R. Apraclonidine reduces intraocular pressure in eyes with increased episcleral venous pressure. J Glaucoma. 1992;1(1):42-43.
5. Bellows AR, Chylack LT Jr, Epstein DL, Hutchinson BT. Choroidal effusion during glaucoma surgery in patients with prominent episcleral vessels. Arch Ophthalmol. 1979;97(3):493-497.
6. Parikh RS, Desai S, Kothari K. Dilated episcleral veins with secondary open angle glaucoma. Indian J Ophthalmol. 2011;59(2):153-155.
7. Rhee DJ, Gupta M, Moncavage MB, et al. Idiopathic elevated episcleral venous pressure and open-angle glaucoma. Br J Ophthalmol. 2009;93(2):231-234.
8. Pradhan ZS, Kuruvilla A, Jacob P. Surgical management of glaucoma secondary to idiopathic elevated episcleral venous pressure. Oman J Ophthalmol. 2015;8(2):120-121.
9. Libre PE. Nonpenetrating filtering surgery and goniopuncture (staged trabeculectomy) for episcleral venous pressure glaucoma. Am J Ophthalmol. 2003;136(6):1172-1174.
10. Audren F, Abitbol O, Dureau P, et al. Non-penetrating deep sclerectomy for glaucoma associated with Sturge-Weber syndrome. Acta Ophthalmol Scand. 2006;84(5):656-660.
Murray Johnstone, MD
• clinical professor, Department of Ophthalmology, University of Washington, Seattle
• (206) 616-1859; firstname.lastname@example.org
Joanne C. Wen, MD
• assistant professor, Department of Ophthalmology, University of Washington, Seattle
• (206) 897-6270; email@example.com