Chapter 228 – Raised Episcleral Venous Pressure
E. RANDY CRAVEN
• Elevated intraocular pressure leading to glaucoma as a result of increased episcleral venous pressure.
• Usually prominent episcleral veins.
• Unilateral elevation of intraocular pressure.
• Blood in Schlemm’s canal.
• Either venous obstruction or arteriovenous abnormalities, rarely idiopathic.
Raised episcleral venous pressure can cause open-angle glaucoma because of obstruction of the outflow of aqueous into the venous drainage system. Because raised episcleral venous pressure can result from systemic abnormalities that ultimately prove fatal, and because of the morbidity associated with these conditions, one needs to be aware of more than eye problems alone.
EPIDEMIOLOGY AND PATHOGENESIS
Glaucoma caused by raised episcleral venous pressure results in a direct effect on intraocular pressure (IOP). When the episcleral venous pressure rises, a similar rise occurs in the IOP. The ultimate IOP is influenced by the production and outflow of aqueous humor but is balanced by the episcleral venous pressure (the Goldmann equation):
The episcleral venous pressure is influenced by body position  and venous drainage pressure in the superior and inferior ophthalmic veins, cavernous sinus, petrosal sinuses, and internal and external jugular veins. Any abnormality that results in an increased venous pressure in the venous drainage system downstream from the eye can produce elevated IOP. As a result of the stagnation of the venous blood, the eye may develop ischemia and subsequent neovascularization.
Idiopathic raised episcleral venous pressure and glaucoma can occur ; color Doppler imaging has not revealed any specific retro-orbital cause. Affected patients tend to be older and have no family history of glaucoma. Unilateral presentation is common, and the right eye is more commonly involved.
The underlying cause of increased episcleral venous pressure that results from raised pressure in the venous drainage system is either venous obstruction or arteriovenous abnormalities ( Table 228-1 ).
Raised episcleral venous pressure results in engorged episcleral veins ( Fig. 228-1 ). The increased venous pressure increases the
TABLE 228-1 — VENOUS AND ARTERIAL ABNORMALITIES THAT RESULT IN ELEVATED EPISCLERAL VENOUS PRESSURE
Tests to Consider
Superior vena cava syndrome
Magnetic resonance imaging
Magnetic resonance imaging
Skin and retina
Jugular vein obstruction
Cavernous sinus thrombosis
Magnetic resonance imaging
Figure 228-1 Prominent episcleral veins. The episcleral vessels are tortuous and appear succulent. The eye lacks the classic ciliary flush seen with iritis or infection.
blood in Schlemm’s canal and can be seen by gonioscopy. If associated ischemia occurs, neovascularization of the iris can be seen. Hemorrhagic choroidal detachments can be seen with secondary angle closure. When the venous pressure approaches the arterial pressure in patients who have arteriovenous abnormalities, the subsequent IOP elevation can be quite high.
Venous obstruction or arteriovenous abnormalities that result in the raised episcleral venous pressure have unique findings (see Table 228-1 ). Proptosis can occur with thyroid eye disease, carotid cavernous fistula, or orbital varix. An orbital varix can have positional proptosis, and a carotid cavernous fistula can cause pulsatile proptosis. Hemangiomas associated with Sturge-Weber syndrome can involve the skin and choroid (“tomato catsup” fundus). Chemosis is common with carotid cavernous fistula and can be seen with Sturge-Weber syndrome or thyroid ophthalmopathy.
Glaucomatous optic atrophy and visual field loss can take longer to develop than in other forms of acute glaucoma and may not occur at all, despite very high IOPs. This is especially true in the more acute problems that present with raised episcleral venous pressure, such as carotid cavernous fistula.
The appearance of the episcleral veins in cases of raised episcleral venous pressure is quite characteristic (see Fig. 228-1 ). It is possible to measure the venous pressure to confirm or determine the raised level. Several methods have been used to determine episcleral venous pressure. The direct method is by cannulation; it is the most accurate method and reveals the normal episcleral venous pressure to be 5–12?mmHg (0.7–1.6?kPa). Noninvasive methods document the collapse of the vein (partial or total). In such methods, a 50% collapse of the vessel is a common endpoint. The noninvasive methods use indirect approaches in which the pressure required for venous collapse is determined by a pressure chamber (of Seidel), air jet, torsion balance, or venometer.   The pressure chamber or venometer methods probably provide the most accurate readings other than those of direct cannulation.
Prominent vessels can occur when there is no glaucoma. Vessels involved with infections, inflammation, or allergies can cause significant injection, but usually the vessels are finer, with a more diffuse hue to the tissue. Ataxia-telangiectasia can cause abnormal vessels on the ocular surface, but these tend to be smaller and more localized to a quadrant. With scleritis and episcleritis, the vessels tend to be smaller in caliber than those found with the raised episcleral venous pressure. Additionally, the vessels have more of a crisscross pattern, with a network of deep vessels and radial vessels, and overall there is a more diffuse involvement. Intraocular tumors can cause prominent scleral vessels (Reese’s sign). Conditions that involve scleral thinning, such as that seen after repeated ciliary body destructive procedures, can result in a more prominent view of the normal veins.
Carotid cavernous fistulae may occur after significant trauma. Pulsating exophthalmos, blurred vision, pain, and chemosis develop, often abruptly, and an audible bruit can be heard. Dural cavernous fistulae have a more gradual onset and typically occur in middle-aged women with no history of trauma. Superior vena cava syndrome occurs in the presence of bronchogenic carcinomas. Cavernous sinus thrombosis occurs from infections that spread from the middle ear, sinuses, or face. Significant congestive heart failure results in elevated venous pressure; many findings are present, such as peripheral edema and pulmonary congestion.
When elevated IOP occurs because of elevated episcleral venous pressure, it can be very difficult to drop the IOP satisfactorily without treating the primary cause of the raised episcleral venous pressure. Treatment for fistulae can involve neuroradiological intervention or neurosurgical intervention. Dural cavernous fistulae are low-flow fistulae and may spontaneously close, whereas carotid cavernous fistulae tend to need intervention to bring about closure. Treatment for the carotid cavernous fistulae includes embolization. Usually, dural cavernous fistulae are watched and may be resolved by sleeping with the head elevated or sitting for a period of time. Thyroid ophthalmopathy can be difficult to treat and is controlled by corticosteroids or by orbital decompression or radiation.
Other medical problems that result in raised episcleral venous pressure should be treated. If this fails or is not possible, medical or surgical intervention is needed. Medications that suppress aqueous production are good first-line choices; beta-blockers and carbonic anhydrase inhibitors are used commonly. Prostaglandin analogs may work but are theoretically limited by outflow. Apraclonidine, because of its vasoconstrictive effects on the arteries that lead into the eye, is also a good first-choice medication.
Laser trabeculoplasty provides little help. Incisional filtration surgery can help lower the IOP, but it is associated with a high incidence of choroidal effusion or hemorrhage ; consequently, some surgeons recommend that scleral windows be placed at the start of the procedure. Preoperative mannitol and other medications that lower pressure may be given. Additionally, the flow through the scleral flap may be adjusted to allow for a higher IOP in the early postoperative period. Where prominent vessels occur, a releasable suture should be considered. Drainage implants may be a good choice if the flow through the implant is kept to a minimum in the early postoperative period.
COURSE AND OUTCOME
Depending on the systemic arterial or venous problem that produced the raised episcleral venous pressure, the glaucoma may be controlled by treating the systemic problem. Once the problem that caused the raised episcleral venous pressure has been treated, the IOP is easier to control. If it is not possible to lower the episcleral venous pressure, such as in Sturge-Weber syndrome, the glaucoma may be chronic and progressive until the IOP can be controlled.
1. Moses RA, Grodzki WJ. Mechanism of glaucoma secondary to increased venous pressure. Arch Ophthalmol. 1985;103:1653–8.
2. Friberg TR, Sandborn G, Weinreb RN. Intraocular and episcleral venous pressure increases during inverted posture. Am J Ophthalmol. 1987;103:523–6.
3. Harris MJ, Fine SL, Miller NR. Photocoagulation treatment of proliferative retinopathy secondary to carotid-cavernous fistula. Am J Ophthalmol. 1980;90:515–20.
4. Minas TF, Podos SM. Familial glaucoma associated with elevated episcleral venous pressure. Arch Ophthalmol. 1968;80:202–8.
5. Lanzl IM, Welge-Luessen U, Spaeth GL. Unilateral open-angle glaucoma secondary to idiopathic dilated episcleral veins. Am J Ophthalmol. 1996;121:587–9.
6. Buus DR, Tse DT, Parrish RK. Spontaneous carotid-cavernous fistula presenting with acute angle closure glaucoma. Arch Ophthalmol. 1989;107:596–7.
7. Brubaker RF. Determination of episcleral venous pressure in the eye. Arch Ophthalmol. 1967;77:110–4.
8. Zeimer RC, Gieser DK, Wilensty JT, et al. A practical venomanometer. Arch Ophthalmol. 1983;101:1447–9.
9. Montzioros N, Weinreb RN. Apraclonidine reduces the intraocular pressure in eyes with increased episcleral venous pressure. J Glaucoma. 1992;1:42–3.
10. Bellows AR, Chylack LT Jr, Epstein DL, Hutchinson BT. Choroidal effusion during glaucoma surgery in patients with prominent episcleral veins. Arch Ophthalmol. 1979;97:493–7.