Glaucoma Secondary to Elevated Venous Pressure
Douglas J. Rhee
Louis R. Pasquale
This group of disorders shares a common mechanism of disease—glaucoma is the result of an elevation of episcleral venous pressure causing elevated intraocular pressure (IOP). Most cases can be attributed to carotid-cavernous sinus (CS) fistulas, CS thrombosis, dural arteriovenous (AV) shunts, superior vena cava syndrome, Sturge-Weber syndrome (SWS), thyroid ophthalmopathy, orbital obstructive lesions, or orbital varices.
Carotid-cavernous fistula (CCF) describes the potentially blinding AV communication between the carotid artery or its branches and the CS.
• CCF is classified as either a direct CCF in which highly pressurized blood from the carotid artery is directly shunted into the venous CS or an indirect CCF, which develops as a result of communication between smaller, low-pressure arterial branches and veins of the CS.1
• Direct CCFs tend to be “high flow” and typically arise in the setting of trauma, whereas indirect CCFs tend to be “low flow” and typically arise congenitally, during pregnancy, or spontaneously in postmenopausal women.1
• Individuals with diseases like Ehlers-Danlos syndrome, collagen deficiency syndromes, or other conditions that weaken the integrity of vessel walls may be at increased risk for spontaneous development of CCFs.
• CCFs alter ocular hemodynamics in a way whereby the high-flow, high-pressure profile of the carotid artery is transmitted to orbital and ocular structures to produce a constellation of ocular signs and symptoms. These signs and symptoms are directly proportional to the degree of abnormal communication between arterial and venous blood in the CS.
• This form of venous hypertension yields the classic clinical triad for CCF:
Unilateral exophthalmos, which may be pulsatile in high-flow direct CCFs
Ocular or cephalic bruit, which is more audible in high-flow CCFs
Injection and chemosis of the conjunctiva, which is more pronounced in high-flow CCFs.1
• Patients with direct CCF have more pronounced complaints of headaches, diplopia, epistaxis, and visual loss than patients with indirect CCFs.1,2
• Indirect fistulas are associated with a myriad of clinical findings that are more subacute or chronic in nature. The presentation of the indirect CCF may include ocular redness and swelling that can be initially construed as an ocular infection. Visual acuity and color vision can be compromised in a gradual manner. There can be extraocular muscle imbalance related to compression of the third and/or sixth cranial nerve in the CS. The proptosis in indirect fistulas is usually more subtle and typically not pulsatile in nature.
• A slit-lamp examination will often reveal arterialized and tortuous, corkscrew conjunctival vessels (Fig. 19-1) and a shallow anterior chamber. The corkscrew appearance distinguishes this condition from episcleritis, where the vessels have a crossing pattern, or scleritis, where there is a deep violaceous hue to ocular surface tissues.
• The IOP is often elevated, and wide mires can be appreciated while the IOP is measured.
• On gonioscopy, the filtration apparatus, that is, angle, may be appositionally closed if choroidal engorgement is present, and blood reflux may be noted where the angle is open. The fundus may exhibit an impending retinal venous occlusive picture with tortuous vessels and intraretinal hemorrhage. The elevated IOP in patients with CCF is often refractory to medical therapy.3
• Orbital imaging with computed tomography or magnetic resonance imaging will reveal enlargement of the extraocular muscles and engorgement of the superior ophthalmic vein (Fig. 19-2). With contrast, enhancement of CS will be evident. Carotid angiography is often diagnostic in revealing the exact fistula site.
• The treatment for both direct and indirect CCFs is the same: Endovascular embolization using balloons or detachable coils or stenting for both types of fistulas is typically definitive in resolving most signs and symptoms (Fig. 19-3).
• A more conservative approach is adopted for indirect CCFs because spontaneous regression can occur. However, in patients with indirect CCF where there is evolution to progressive ocular and orbital congestion with compromise of vision and intractably elevated IOP, definitive closure is indicated.1,4
• Filtration surgery is to be avoided in eyes with CCFs if at all possible.
FIGURE 19-1. Carotid-cavernous fistula. Arterialization of conjunctival vessels in a 78-year-old patient with a spontaneous indirect carotid-cavernous fistula before endovascular embolization with a detachable coil. (Courtesy of Dr. Peter Veldman.)
FIGURE 19-2. Carotid-cavernous fistula. A magnetic resonance angiography of the patient in Figure 19-1 revealing an enlarged right superior ophthalmic vein. (Courtesy of Dr. Peter Veldman.)
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