Sonal Desai Wadhwa,
Eve Juliet Higginbotham
The diagnosis and management of open-angle glaucoma secondary to increased episcleral venous pressure (EVP) is sometimes challenging. The diagnosis can be easily missed if the clinical presentation does not show evidence of an obvious sign such as pulsatile exophthalmos. If unprepared, the unsuspecting ophthalmic surgeon may encounter unexpected intraoperative complications such as choroidal hemorrhage. Moreover, the management of some cases may involve other physicians such as a neuroradiologist, an oncologist, or a neurosurgeon. It thus behooves the clinician to be fully aware of the clinical entities associated with elevated EVP.
The importance of the role of EVP in aqueous dynamics has evolved over several decades. The aqueous veins are important contributors to EVP. The relationship between aqueous veins and aqueous outflow began to be recognized when Lauber, in the early 1900s, provided histologic evidence that the canal of Schlemm was connected to the episcleral venous network.[1] Several investigations were made with animals, and the results suggested a functional link between the anterior chamber and the aqueous veins. Lauber[1] noted in 1901 the dilution of red blood cells in the anterior ciliary veins of the dog compared with an aliquot of blood taken from the paw of the same animal. In 1923, Seidel[2] injected India ink into the anterior chamber of a rabbit and subsequently noted the appearance of the ink in the episcleral veins. As a natural extension of these observations in animals, Ascher[3,4] noted the presence of aqueous veins in humans and described their physiologic importance to aqueous flow in 1942. These vessels, which were once thought to be empty, were described as containing clear fluid, the aqueous humor. Ascher's observations sparked great interest in aqueous veins, the pressure generated within these vessels, and the influence of EVP on intraocular pressure (IOP).
The diagnosis of glaucoma secondary to elevated EVP can be divided into three general areas: arteriovenous anomalies, venous obstruction, and the idiopathic variety (Table 211.1).[5] The first category, arteriovenous anomalies, can be subdivided into six entities: carotid-cavernous sinus fistula (CCF), orbital varices, Sturge-Weber syndrome (SWS), orbital-meningeal shunts, carotid-jugular venous shunts, and intraocular vascular shunts. Venous obstruction can present as a retrobulbar tumor, thyroid ophthalmopathy, superior vena cava syndrome, congestive heart failure, thrombosis of the cavernous sinus or orbital vein, vasculitis involving the episcleral vein or orbital vein, and jugular vein obstruction. Finally, patients may present without any apparent cause for elevated EVP and may show evidence of either a sporadic or familial form of the disease. A brief review of the anatomy of the ocular and orbital venous system and the physiology and various methods of measuring EVP provides the reader with a general foundation for understanding the basic mechanism of this secondary open-angle glaucoma before each of the specific disorders is discussed.
TABLE 211.1 -- Classification of Elevated Episcleral Venous Pressure
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Venous Obstruction |
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Retrobulbar tumor |
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Thyroid ophthalmopathy |
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Superior vena cava syndrome (mediastinal tumor) |
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Congestive heart failure |
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Thrombosis of cavernous sinus or orbital vein |
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Vasculitis involving episcleral vein or orbital vein |
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Jugular vein obstruction |
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Arteriovenous Anomalies |
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Carotid cavernous sinus fistula |
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Orbital varix |
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Sturge-Weber syndrome |
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Orbital-meningeal shunts |
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Carotid-jugular venous shunts |
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Intraocular vascular shunts |
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Idiopathic Elevation of Episcleral Venous Pressure |
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Sporadic |
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Familial |
From Weinreb RN, Jeng S, Goldstick BJ: Glaucoma secondary to elevated episcleral venous pressure. In: Ritch R, Shields MB, Krupin T, (eds): The glaucomas. St. Louis: CV Mosby; 1989: p 1130.
ANATOMY OF THE EPISCLERAL VENOUS SYSTEM
According to Duke-Elder and Wybar,[6] the ciliary circulation consists of the vortex system, the anterior ciliary system, and the posterior ciliary system. The vortex system drains most of the choroid, ciliary body, and iris. The venules of the choroid, arising from the choriocapillaris, converge with neighboring venules to form subsequently larger veins that pass to the outer layer of the choroid. The larger veins subsequently converge to form a single vortex vein in each quadrant. The vortex veins drain into the posterior ciliary veins, which subsequently drain into the orbital veins.[7] The venous drainage of the ciliary body consists of venous blood from the ciliary muscle and processes that subsequently passes posteriorly into the vortex vein. The iris veins drain into the ciliary body and eventually enter the vortex venous system.
The drainage of blood from the anterior and outer regions of the ciliary body makes up the anterior ciliary venous system.[6] The branches of this system connect with the efferent channel of the canal of Schlemm before linking up with the episcleral venous plexus. The anterior ciliary veins form a deep and superficial plexus. The deep plexus, which consists of numerous flat and tortuous veins, communicates directly with the canal of Schlemm through collector channels. The superficial portion of the plexus drains directly into the episcleral venous plexus. Other authors have referred to these systems as indirect and direct venous drainage systems, respectively.[5] This anterior ciliary venous system communicates with the venous plexuses of Tenon's capsule and conjunctiva and eventually drains into the ophthalmic veins. The posterior ciliary venous system is relatively unimportant.[6] This system primarily drains the posterior portion of the sclera.
There are variable anastomoses connecting the retinal and ciliary venous systems.[8] Anastomotic channels are noted between the retinal venous system and the vortex system when central venous pressure is high.[9] However, no significant connection between the vortex veins and the episcleral veins in humans has been noted.[8]
The three major routes of venous drainage in the orbit are the superior ophthalmic vein, the inferior ophthalmic vein, and the facial veins, all of which are interconnected (Fig. 211.1).[10] The superior ophthalmic vein, located in the upper and medial aspects of the orbital margin, is formed by the supraorbital and angular veins of the face. The angular vein establishes a link between the superficial veins of the face via the anterior facial vein and the deep veins of the orbit. The superior ophthalmic vein leaves the orbit via the superior orbital fissure and then traverses downward to the cavernous sinus. Along its course there may be varicosities that may contribute to a pulsating exophthalmos.[6] The two superior vortex veins and branches of the ethmoid venous system drain into the superior ophthalmic vein. The inferior ophthalmic vein receives branches from the lower lid, the area surrounding the lacrimal sac, the inferior rectus, and inferior oblique muscles, and two inferior vortex veins. Along its course, the inferior ophthalmic vein divides into two branches. The superior branch may either pass through the superior orbital fissure, beneath the annulus of Zinn, and enter the cavernous sinus or enter into the superior ophthalmic vein. The inferior branch, if present, passes through the inferior orbital fissure and ultimately drains into the pterygoid plexus.
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FIGURE 211.1 Venous drainage of the orbit. |
There are three principal directions of blood flow through the orbital venous system. Flow may be backward via the superior and inferior ophthalmic veins to the cavernous sinus and the cranial system. Venous drainage may also be directed forward via anastomoses of the ophthalmic veins to the facial system. Moreover, flow may be downward to the pterygoid venous plexus.[6]
PHYSIOLOGY OF EVP
EVP plays a significant role in aqueous humor dynamics. Aqueous humor, which is produced primarily by a combination of ultrafiltration, diffusion, and active transport in the posterior segment, passes through the pupil and exits the eye by one of two pathways: (1) by way of the anterior surface of the ciliary body or (2) through the trabecular meshwork, Schlemm's canal, collector channels and, subsequently, aqueous veins. These pathways have been termed alternatively unconventional and conventional pathways, respectively.[4,11] Flow of fluid by way of the unconventional pathway is independent of pressure. Outflow via the conventional route is passive and depends largely on the difference between the pressure within the eye (IOP) and EVP. Fluid therefore naturally flows in the direction of the lower pressure-EVP. However, there is resistance (R) within the conventional outflow system, particularly across the juxtacanalicular trabecular meshwork. The relationship between these parameters is thus:
[1] 
As EVP increases in relation to IOP, or as resistance increases, flow decreases. However, resistance does not necessarily remain constant when there are changes in IOP and it may actually increase as the IOP increases because of collapse of the aqueous outflow system. Equation [1] would therefore be modified as follows[12]:
[2] 
where Ri is the initial resistance measured when the IOP and EVP are equivalent and Q represents the change in resistance after an increase in the difference of IOP and EVP measuring 1 mmHg. Incorporating eqn [2], eqn [1] would be written:
[3] 
This equation suggests that EVP can influence flow within the conventional outflow pathway in two ways; the pressure gradient and resistance.
At steady state, aqueous production (Fap) should be equal to flow across the conventional pathway (Fc) added to flow across the unconventional pathway (Fu):
[4] 
Using eqn [1] as an approximation of flow across the conventional pathway, the following equation arises:
[5] 
Solving for IOP, eqn [5] appears as follows:
[6] 
It should be noted that EVP may not be independent of IOP and aqueous production. The latter may decrease when IOP increases, a concept referred to as pseudofacility. When the EVP was increased in an experimental study, the IOP was noted to increase 80% of the increment. The 20% difference was thought to be due to a decrease in aqueous production or to the egress of fluid via pathways other than the anterior chamber.[13] The existence of pseudofacility, however, has not been documented fluorophotometrically.[14]
The relationship of IOP and EVP has been studied by several investigators. Using a micropuncture technique, Maepea and Bill[15] evaluated the correlation of IOP and EVP in cynomolgus monkeys. A positive relationship linking these variables was noted and was expressed as follows by these investigators:
The increase in EVP induced by increasing IOP in these animals was not statistically significant. Similarly in humans, a positive correlation (+0.59) was noted by Weigelin and Lohlein[16] in 172 individuals with IOPs ranging from 7 to 24 mm Hg. Moreover, when IOP and EVP were measured in individuals in both the supine and the head-down vertical positions, an increase in EVP of 0.83 (0.21 mmHg) was reported for every 1-mmHg rise in IOP.[17] Kaskel and co-workers[18] noted an increase in EVP more than IOP when individuals changed from a sitting position to a recumbent position. Finally, the EVP as well as IOP were noted to be lower during the third trimester of pregnancy.[19]
In contrast, a negative correlation between IOP and EVP has been noted by others. Talusan and co-workers[20] reported on findings in normotensive eyes and in eyes with primary open-angle glaucoma. A decrease in EVP from 8.5 to 6 mmHg corresponded with an increase in IOP from 20 to 40 mmHg. Similarly, Kupfer[21] noted a lower mean EVP in normotensive eyes, 8.4 (0.3 mmHg) versus ocular hypertensive eyes, 7.7 (0.2 mmHg). Differences in IOP between eyes could not be attributed to differences in EVP according to Podos and co-workers.[22]
The impact of EVP on aqueous humor dynamics is indeed complex and depends mainly on variations in the clinical circumstance as well as on methods of measurement. Certainly, eqn [6] suggests a positive correlation existing between IOP and EVP. However, considering the confusion in the literature, these calculations are mere approximations. Additional clinical evaluation is needed to untangle the existing controversies.
METHODS OF MEASURING EVP
There are essentially four noninvasive methods for determining EVP: torsion balance, pressure chamber, air jet, and an indirect method. The accuracy of the end-point of the different methods has been investigated by both Brubaker[23] and Gaasterland and Pederson.[24]
In 1949, Goldmann[25] described the torsion balance method as a technique based on the assumption that a known force applied to a known area of conjunctiva increases the pressure within the vessel by an amount equivalent to the applied force per unit area. Essentially the torsion balance device consists of a lever connected to a suspended torsion spring. The diameter of the tip that is in contact with the eye measures 0.5 mm. Increasing degrees of pressure are applied to the conjunctiva until the desired end-point is reached. The average value for EVP obtained using this method is 10.0 (1 mmHg).[11]
The pressure chamber method was described by Seidel[26] in 1923. This device is based on a similar principle as the torsion balance method. One side of a small chamber consists of a thin, distensible membrane, and the other side consists of a transparent glass through which the episcleral vein is directly viewed. The membrane is in contact with the vessel and the pressure within the chamber increases until the desired end-point is reached. The pressure within the chamber is assumed to be comparable to the pressure within the vessel. Zeimer and associates[27] developed a commercially available device that can be easily mounted on a slit lamp and requires only one observer to complete the measurement (Fig. 211.2). A mean value for EVP measuring 9.8 (1.8 mmHg) using this pressure chamber method has been noted.[11]
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FIGURE 211.2 Episcleral venomanometer based on the pressure chamber method. This instrument mounts easily on the slit-lamp microscope, the membrane is positioned in contact with the episcleral vessel, and the graduated wheel measures the episcleral venous pressure in millimeters of mercury. |
Krakau and associates[28] described the air jet method which is a noninvasive method of determining EVP that requires no topical anesthetic. The force that is required to achieve the desired end-point is measured. Widakowich[29] underscored the importance of measuring EVP in a vein as close to Schlemm's canal as possible using this method. Krakau and associates[28] reported a mean value of 10.4 (0.8 mmHg) using an air jet device.
In the indirect method, the eye is first compressed with an impression tonometer. The IOP rapidly decreases and then increases to a level equal to the EVP. The average pressure measured using this method is 10.4 (4.1 mmHg).[11,30]
CLINICAL ENTITIES ASSOCIATED WITH ELEVATED EPISCLERAL VENOUS SYSTEM
ARTERIOVENOUS ANOMALIES
Carotid-Cavernous Sinus Fistula
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Key Features |
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Carotid-cavernous sinus fistula (CCF) is an arteriovenous shunt between the internal or external carotid arteries and the cavernous sinus. Based on clinical and angiographic differences, this entity has been further classified into two subcategories; traumatic (high flow, direct fistulas) and spontaneous (low flow, indirect fistulas).[31] The 'traumatic' presentation is typically a young individual who presents after a severe head injury with pulsating exophthalmos, conjunctival chemosis, engorgement of the episcleral vein, severely restricted ocular motility, bruit, and ocular ischemia. The proptosis can increase slowly for several weeks before stabilizing. Lid swelling as well as dermal cyanosis may be particularly evident if the superior ophthalmic vein is significantly enlarged. An ocular bruit can be noted in 50-95% of patients and is amplified with exercise. Diplopia, due to the involvement of the cranial nerves (most often the sixth cranial nerve), may be a presenting complaint as well; mechanical restriction may also be noted. Patients may have retrobulbar pain that may be associated with a constant noise and a bruit.[32] The provoking injury can be a basal skull fracture or any penetrating injury to the orbit injuring the medial or inferomedial wall of the orbit as well as the superior orbital fissure. Such trauma can account for 75% of the cases of carotid-cavernous fistulas.[32] These fistulas can also occur after surgery involving the internal carotid artery or after a rupture of a preexisting aneurysm of the internal carotid artery. Visual loss and papilledema have also been associated.[33]
An incidence of 50% loss of vision has been reported from damage to the optic nerve associated with the initial injury, papilledema, venous congestion of the retina, and chronic secondary glaucoma.[32]Glaucoma can occur secondary to increased EVP, orbital congestion, neovascularization after central retinal vein occlusion, or angle closure.
The 'spontaneous' clinical entity usually has a more insidious presentation. These fistulas involve small intracavernous dural branches of the internal carotid artery and dural branches from the ascending pharyngeal and internal maxillary arteries from the external carotid artery. This communication may involve the ipsilateral or contralateral cavernous sinus. There may be drainage either anteriorly via the superior ophthalmic vein, the deep sylvian vein, or the sphenoparietal sinus or posteriorly via drainage by way of the superior and inferior petrosal sinuses. If there is no significant anterior drainage, these fistulas may be asymptomatic.[33] Typically, a middle-aged to elderly individual presents with minimal proptosis without pulsations, arterialized episcleral veins, and usually no history of trauma (Figs 211.3 and 211.4). Of 20 patients diagnosed as having a spontaneous carotid-cavernous fistula, one patient had papilledema, four patients had choroidal detachment, two patients demonstrated exudative retinal detachment, and three patients had central venous thrombosis.[34] In elderly patients, there may be a predisposition to the development of carotid- cavernous fistulas resulting from degenerative vascular changes within the sinus.[32] These spontaneous fistulas have also been reported in association with Ehlers-Danlos syndrome[35] and pseudoxanthoma elasticum.[36] In 64 patients reported by Jorgensen and Guthoff,[37] spontaneous CCF accounted for 31% of the secondary glaucomas associated with elevated EVP. Other clinical entities that should be differentiated from these fistulas include dysthyroid orbitopathy, pseudotumor of the orbit, orbital cellulitis, episcleritis, and any sphenoorbital mass lesion.[33]
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FIGURE 211.3 Dilated episcleral venous vessels and proptosis in a patient with a carotid-cavernous fistula. |
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FIGURE 211.4 Proptosis, chemosis, and arterialization of episcleral venous vessels in a patient with a carotid-cavernous fistula. |
The diagnosis of a carotid-cavernous fistula is made clinically and radiographically. Intra-arterial angiography is the gold standard for diagnosis. Miller[33] points out the importance of performing not only selective internal carotid arteriography but also selective external carotid arteriography, particularly when a dural cavernous fistula is suspected. Dural fistulas have been noted to close spontaneously after angiography. Three of five patients with dural arteriovenous shunts were noted to improve spontaneously after angiography in one group of patients.[38] If intra-arterial angiography is unavailable or indeterminant other non-invasive methods can be used. Ocular pulse amplitude, as measured by pneumotonometry, has been shown to be a useful noninvasive tool to evaluate patients with CCF. In 15 patients with carotid-cavernous fistulas, the difference in the ocular pulse amplitude between eyes was noted to be greater in patients with fistulas than in patients without orbital disease and patients with orbital disease without any evidence of a fistula (Golnik KC, Miller NR: The diagnosis of carotid- cavernous sinus fistulas by ocular pulse amplitude. Presented at the North American Neuro-Ophthalmology Society Meeting, Park City, Utah; 1991). CT angiography, CDUS (color Doppler ultrasonography),[39] and MR angiography can also be used. These radiographic techniques may demonstrate enlargement of the extraocular muscles, dilatation of the superior ophthalmic vein, and enlargement of the cavernous sinus (Fig. 211.5).
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FIGURE 211.5 Computed tomography scan of a dilated superior ophthalmic vein in the patient depicted in Figure 211.4. |
There are three treatment options for these fistulas: observation as some may close spontaneously, carotid occlusion/ligation, or carotid preservation techniques (i.e., transarterial balloons, coils, or stents). If observation is chosen the symptoms may resolve as the fistula closes, however, sometimes the symptoms and signs may worsen if there is spontaneous thrombosis of the superior ophthalmic vein.[40]Systemic steroids may be beneficial in these cases.[33] However, spontaneous improvement has been reported.[40]
If intervention is chosen then depending on the vessel feeding the shunt, treatment may involve ligation of the carotid artery proximal to the ophthalmic artery or embolization. However, external ligation of the carotid artery has been mostly replaced by interventional radiology endovascular approaches.[41] Hanneken and co-workers[42] successfully treated four patients, three of whom showed evidence of a spontaneous fistula and one who had a traumatic fistula. A detachable balloon was advanced through the superior ophthalmic vein. There were no intraoperative or postoperative complications. Nevertheless, any intervention with respect to these fistulas must be balanced by the relevant risks.[31,43-44]
In cases that are complicated by secondary open-angle glaucoma, aqueous suppressants can be used initially. Prostaglandin analogues may not be effective in these cases. Miotics may increase the inflammation in an already injected eye. Since most cases of the dural arteriovenous fistula resolve spontaneously, the pressure can be controlled until the fistula resolves. Laser trabeculoplasty in these patients can result in choroidal effusion and a flat anterior chamber (Robert Ritch, personal communication). Angle-closure glaucoma has been reported in association with dural shunts. In such cases, orbital congestion plays a significant role. Choroidal effusions may be present in addition to a dilated superior ophthalmic vein. These patients can be treated initially with aqueous suppressants as well as with hyperosmotic agents. Laser iridotomy can be performed to eliminate the contribution of pupillary block. Cycloplegic agents can be added to encourage a posterior shift of the lens-iris diaphragm. Laser iridoplasty or goniosynechialysis may be beneficial in further opening the angle. If neovascular glaucoma occurs as a result of ocular ischemia, panretinal photocoagulation is indicated.[45]
Orbital Varix
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Key Features |
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A shunt between the intracranial and extracranial venous systems forms the orbital venous plexus. An orbital varix can be created when there is dilatation of the orbital veins as a result of posterior dilatation of the intracranial vessels.[32] Alternatively, an orbital varix may be congenital and occur as an abnormal, tortuous, dilated vein.[46] Orbital varix has also been associated with the Klippel-Trenaunay-Weber (KTW) syndrome.[47] A common clinical sign of an orbital varix is intermittent exophthalmos, which occurs by placing the head in a dependent position, by sneezing, or by performing a Valsalva maneuver. By increasing pressure within the jugular vein, the orbital varix becomes distended, resulting in proptosis. These episodes may be associated with symptoms of blurred vision, headache, nausea, and pain. When the patient ceases the inciting maneuver, the proptosis lessens. Over a period of years, these episodes may become longer and more difficult to reverse.[32] A 15% incidence of blindness has been noted as a result of optic nerve damage after repeated episodes of proptosis.[48] The presence of associated systemic venous abnormalities, e.g., involving the buccal mucosa, extremities, and abdomen, should be investigated.[32]
Occasionally, patients may present with orbital varix thrombosis. There may be symptoms indicative of an acute orbital process (i.e., pain, diplopia, blurred vision, and proptosis). Bullock and associates[49]described three patients who presented with orbital varix thrombosis. All three patients had a characteristic body habitus, a 'bull neck,' that may have contributed to the stagnation and subsequent thrombosis of their orbital varices. The authors pointed out the importance of differentiating this clinical entity from cavernous sinus thrombosis and superior ophthalmic vein thrombosis. Only one of the three patients had glaucoma.
The diagnosis of an orbital varix can be made both clinically and radiographically. Various radiographic methods can be used such as: orbital venography, computed tomographic angiography (CTA), MRV, and color-doppler ultrasonography. CTA is currently the most commonly used study as it is fast, noninvasive, and readily available.[50] CTA particularly if combined with jugular compression or the Valsalva maneuver,[51,52] as well as MRI, can assist the clinician in making the diagnosis.[53]
Treatment options for orbital varices include: observation[49,54-57], endovascular embolization[58], electrically induced thrombosis[59] or surgical excision.[46,54,57-61] Since many of the varices eventually resorb or recanalize, with subsequent improvement of symptoms, conservative management is usually suggested. However, sometimes surgical intervention becomes necessary. Indications for surgery include repeated or unrelenting episodes of thrombosis, intractable pain, severe proptosis, and compressive optic neuropathy.[49] The glaucoma, which is secondary to elevated EVP and decreased outflow facility, can be managed medically.[62]
SWS (Encephalotrigeminal Angiomatosis)
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Key Features |
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A hemiparetic, epileptic patient with a facial hemangioma was presented to the Clinical Society of London by Sturge in 1879. He postulated that the facial manifestations were related to the neurologic component of the presenting patient's disorder. Previously, in 1860, Schirmer had presented a patient with a facial hemangioma and buphthalmos but no evidence of involvement of the central nervous system. In 1910, Durck was the first to report the presence of cerebral calcification in association with a facial nevus. Weber characterized the radiologic appearance of a case similar to that of Sturge, and the disorder has subsequently been called the SWS. Alternatively, the term encephalotrigeminal angiomatosis has been proposed because of the involvement of the trigeminal nerve. Others favor the label encephalofacial angiomatosis because the facial lesion may extend beyond the distribution of the trigeminal nerve.[63]
SWS is characterized by a cutaneous hemifacial angioma that stops at the midline and an ipsilateral angioma of the meninges and brain (Fig. 211.6) usually affecting the parietal lobes. Other characteristics that may be noted are epilepsy, intracranial calcifications, cortical necrosis, glaucoma, severe headaches, mental retardation, hemiparesis, and a homonymous hemianopia.[63] The characteristic facial hemangioma is unilateral in 90% of cases and can involve the lower face, scalp, and neck.[64] Glaucoma has been reported to occur in 30% of cases.[10,65] Sixty percent of patients acquire glaucoma before 2 years of age, and the remaining patients acquire it later in childhood or early adulthood.[66-67] A study that examined the prevalence of glaucoma among 52 adults aged 18-63 years noted a higher prevalence of 60%.[68] Glaucoma is often present in the ipsilateral eye when the facial angioma involves the eyelid or conjunctiva.[69] In an evaluation of 106 patients with facial port-wine stains and SWS, involvement of the first division of cranial nerve V was the determinant of ocular involvement.[70] An angioma of the choroid can be found in 31[71]-50%[72] of patients with SWS. The choroidal hemangioma found in SWS is flat and diffusely involves the choroidal vasculature. There is often associated diffuse angiomatosis involving the episcleral and subconjunctival perilimbal tissues.[73] Other less commonly seen ocular abnormalities include iris heterochromia and retinal vascular tortuosity.[74]
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FIGURE 211.6 Young patient with facial angioma and ipsilateral glaucoma. No cerebral involvement has been documented. |
When extensive cutaneous vascular malformations occur in addition to oculodermal melanocytosis, the term phakomatosis pigmentovascularis is applied. Teekhasaenee and Ritch[75] described nine patients with this syndrome. Congenital glaucoma occurred in 10 eyes that had evidence of both the melanocytosis and the vascular malformation. The authors noted that glaucoma was more likely to occur when the vascular malformations were present rather than the hyperpigmentation. This syndrome occurs primarily in Asians.
Patients with KTW can also exhibit angiomas of the face and extremities and associated ocular findings similar to those of SWS, but in addition these patients show evidence of varicosities on the affected side as well as local hypertrophy or atrophy of the bone and soft tissues in the involved areas.[33,65,76] Other closely related disorders include Jahnke's syndrome (facial angioma without glaucoma), Schirmer's syndrome with buphthalmos, Lawford's syndrome with late-onset glaucoma, and Mille's syndrome with a choroidal hemangioma without glaucoma.[67]
There have been many theories to explain the cause of the glaucoma associated with SWS.[63-64,66] The neural theory proposes a congenital modification of the sympathetic innervation to the eye resulting in dilatation of the uveal capillaries and a decrease in blood flow. This theory would suggest that heterochromia of the iris would be more commonly seen. Moreover, Horner's syndrome, which is characterized by a sympathetic abnormality, is not associated with glaucoma. The cranial theory suggests that an occult angioma of the meninges interferes with tributaries draining into the cavernous sinus. However, there are instances when patients have evidence of glaucoma without intracranial angiomas. Since choroidal hemangiomas are often noted, some investigators have proposed a hypersecretion theory- i.e., transudation of fluid from the choroidal hemangioma resulting in glaucoma. However, unless there are specific characteristics of the choroidal hemangioma associated with SWS that distinguish it from a hemangioma occurring alone without glaucoma, this theory does not seem valid. Other theories include the mechanical blockage of the aqueous outflow system by an angioma in the angle and angle closure secondary to peripheral anterior synechiae.
There is a theory that deserves particular attention; a decrease in outflow facility either due to malformation of the aqueous outflow system or secondary to elevated EVP. Several investigators have noted changes in the angle similar to those found in congenital glaucoma.[10,63,65,77-79] A 'high' insertion of the iris and ciliary muscle and the existence of a 'Barkan membrane' have been described. Cibis and co-workers[67] analyzed the trabeculectomy specimens taken from patients with SWS noting a compact trabecular meshwork with amorphous material filling the deeper intertrabecular spaces (Fig. 211.7). The beams appeared much thicker than what might be expected for the patients' ages. These changes were reminiscent of primary open-angle glaucoma. There were also anomalous vessels noted. Mwinula and co-workers[80] reported a case of a 20-year-old woman with SWS who had evidence of a cluster of anomalous vascular-like structures in a trabeculectomy specimen. There was also an abnormal accumulation of fine granular extracellular matrix material noted in the juxtacanalicular tissue (JCT) and surrounding the vessels. Akabane and Hamankaka also examined the trabeculectomy specimen of a 10 year old child with SWS and found that the ciliary muscle was dislocated anteriorly and Schlemm canal was not present. They also found the spaces in the JCT were replaced by vascular and connective tissue.[81] Phelps[64] raised three objections to any theory based solely on anterior chamber malformation: (1) the pathophysiology of congenital glaucoma is poorly understood; (2) the typical changes seen in infants are not seen in older patients with SWS; and (3) the vascular component of this syndrome is such an overwhelming feature of this entity, it is difficult to exclude its contribution. However, given the evidence provided by histologic examination of surgical specimens, one cannot discount a primary obstruction in the aqueous outflow pathway.
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FIGURE 211.7 Light micrograph of a trabeculectomy specimen from a patient with Sturge-Weber syndrome. Note the compact trabecular meshwork (TM) and pericanalicular region (P). SC, Schlemm's canal. ×800. |
In 1971, Weiss[10] proposed that the glaucoma observed in SWS was secondary to elevated EVP. He suggested that the arteriovenous shunts within an episcleral hemangioma increased the pressure within the vessels draining Schlemm's canal. In support of Weiss' theory, Phelps[64] noted an elevation in EVP in 12 glaucomatous eyes associated with SWS measuring 18.5 (5.8 mmHg) compared with 9.1 (1.6 mmHg) in the uninvolved fellow eyes. Episcleral hemangiomas[82] and elevated EVP[83] have been noted by others. Those who refute this theory point out the surgical success of procedures such as goniotomy and trabeculotomy in these cases as evidence that a primary abnormality in the aqueous outflow system is the primary mechanism. It is likely that the basis of the glaucoma seen in SWS is a combination of an anomaly in the anterior chamber as well as elevated EVP.[84]
An analysis by Iwach and co-workers[69] lends insight into the management of glaucoma associated with SWS both medically and surgically. Thirty-six eyes of 30 patients with either early- or late-onset glaucoma with a mean follow-up of 122 months were reviewed. Primarily a surgical approach was used for infants, and a combination of medications, laser trabeculoplasty, and goniotomy, trabeculotomy, or trabeculectomy was used in late-onset cases. Median postoperative intervals during which the patients were considered stable based on IOP or absence of disk deterioration were calculated for each of the interventions and were reported as follows: goniotomy (12 months), trabeculotomy (21 months), trabeculectomy (21 months), argon laser trabeculoplasty (25 months), and medications (57 months). The authors favored either goniotomy or trabeculotomy because trabeculectomies were complicated by a 24% incidence of intraoperative choroidal effusions while goniotomies and trabeculotomies had no intraoperative choroidal effusions. Choroidal effusion[85] and expulsive hemorrhage have been noted to be a significant problem intraoperatively by others as well.[86] Bellows and associates[87] suggest performing a posterior sclerotomy before entering the eye when undertaking filtration surgery to allow adequate drainage of any choroidal effusion that might occur intraoperatively. However, more recent reports do not advocate the use of prophylactic posterior sclerotomy intraoperatively. In a retrospective case series of 17 consecutive trabeculectomies for patients with either SWS or KTW without posterior sclerotomy there were no cases of intraoperative choroidal hemorrhage or effusion. Six patients did develop transient postoperative choroidal effusions which resolved spontaneously. Therefore, the authors did not recommend prophylactic sclerotomy.[88] Ali and co-workers[89] advocate avoiding the occurrence of a choroidal effusion in their cases by using a releasable suture and tightly suturing the scleral flap. Others favor combining procedures such as trabeculotomy-trabeculectomy[90] and trabeculectomy and cyclocryotherapy.[91] Agarwal and co-workers[92] reported their experience after combined trabeculotomy- trabeculectomy. In a series of 16 patients (18 eyes) and a mean follow-up of 42 months, IOP was less than or equal to 22 mmHg in 11 eyes. However, hyphema occurred in 22.2%, vitreous loss in 16.7%, and choroidal detachment in 16.7% of these eyes.
The use of setons has also been recently studied in the treatment of SWS. In a review by Celebi et al the authors sought to determine the safety of the use of Ahmed valves for SWS. They reviewed seven patients with SWS after Ahmed valve placement and found no evidence of intraoperative suprachoroidal hemorrhage. Their surgical technique used an anterior chamber maintainer to minimize pressure changes during surgery.[93] Hamush and colleagues investigated to determine the efficacy of Ahmed valve in lowering IOP. They reviewed 11 eyes of 10 patients and defined success as an IOP of less than 21 mmHg. The cumulative probability of success was 79% at 24 months and 30% at 60 months.[94] Budenz and collegues also reported their experience on 10 eyes of nine patients who underwent Baerveldt glaucoma implant for SWS. Average follow-up was 35 months and it was found that all eyes had IOP less than 21 mmHg with mean IOP 16.9 +/- 2.3 with a mean use of medications 1.1 (preoperative mean IOP was 24.8 +/- 6.2 mmHg with mean 1.8 +/-1.0 medications).[95] Therefore, seton placement also has a place also in the management of SWS.
Keverline and Hiles[96] emphasize the importance of early intervention before worsening of the glaucomatous status. Of the 35 eyes evaluated by Iwach and co-workers,[69] 23 eyes showed evidence of IOP less than 25 mmHg and 13 eyes demonstrated visual acuity better than 20/40 at the patients' last visit. Adjunctive use of mitomycin C with filtration surgery should also be considered, particularly considering the success of these approaches in refractory cases.[97]
Miscellaneous Arteriovenous Anomalies
Orbital-meningeal shunts, carotid-jugular venous shunts, and intraocular vascular shunts are clinical entities that are also associated with elevated EVP.[5] Michelsen and associates[98] distinguish vascular malformations from vascular neoplasms such as hemangiomas. Vascular malformations can be further subdivided into venous malformations without an arterial component (orbital varix), true arteriovenous malformations of the orbit, and arteriovenous malformations that are primarily extraorbital but with orbital manifestations. Frequent physical findings are pulsating or nonpulsating exophthalmos, chemosis, restricted ocular motility, visual loss, glaucoma, and a bruit.
Howard and co-workers[99] reported a case of a 19-year-old patient who presented with progressive swelling of the upper lid and proptosis. Cerebral angiography documented the presence of an arteriovenous malformation that was supplied primarily by a distal branch of the internal maxillary artery as well as by the superficial temporal and middle meningeal arteries. The lesion was treated initially by embolization of a rapidly polymerizing polymeric silicone (Silastic) liquid but subsequently required surgical removal after a recurrence 4 years later. Arteriovenous malformations[100-101] and aneurysms[102-103]within the orbit can mimic orbital tumors. Angiography can establish the diagnosis. The associated glaucoma is due to the increased pressure within the vortex veins that is secondary to increased orbital pressure.[102-103] The glaucoma can be treated initially with topical medications and carbonic anhydrase inhibitors; however, treatment of the underlying problem must be undertaken to achieve long-term stabilization of the glaucoma.[103]
VENOUS OBSTRUCTION
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Key Features |
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RETROBULBAR TUMOR
Proptosis is the most significant clinical sign seen in association with orbital tumors. Any difference of 2 mmHg or more of protrusion of the globes when comparing two orbits should raise suspicions of orbital disease until it is proved otherwise.[65] Depending on the size and consistency of the lesion, the secondary orbital congestion can lead to an increase in EVP.[103-104] Tumors that occur commonly in the region of the superior orbital fissure and the cavernous sinus include meningiomas, pituitary adenomas, and metastatic tumors. The diagnosis can be confirmed using neuroimaging studies and ultrasonography. These tumors may be treated medically, surgically, or radiotherapeutically.[45] The underlying cause must be treated to achieve long-term stabilization of the IOP.[103]
THYROID OPHTHALMOPATHY
Thyroid ophthalmopathy is characterized by proptosis, restriction in ocular motility, a decrease in orbitonometry readings, conjunctival chemosis, epiphora, papilledema, refractive changes, ocular discomfort, and elevation in IOP.[105] The mechanism of the increase in IOP may occur by a variety of mechanisms: elevated EVP due to orbital congestion, contraction of the extraocular muscles, chronic exposure leading to chronic inflammation and secondary angle closure[5] and, finally, increased mucopolysaccharide deposits within the aqueous outflow system.[106] There is no evidence of direct influence of the thyroid on IOP.[107] A 5% incidence of glaucoma was reported in one series of patients.[106] In the same series of 74 patients, the degree of proptosis correlated with the likelihood of finding elevation in IOP. In another series of patients, two of 29 individuals had evidence of glaucoma and 11 demonstrated a reduced outflow facility (Po/C as measured by tonography > 100).[107] Patients with glaucoma can be treated with topical medications and carbonic anhydrase inhibitors. It is unlikely that prostaglandin analogues will be effective. Treatment of the thyroid disease is necessary and may involve orbital decompression or systemic steroids.[105]
SUPERIOR VENA CAVA SYNDROME
The presenting signs characterizing the superior vena cava syndrome include edema of the lid, face, and conjunctiva; vascular engorgement of the fundus, episclera, and conjunctiva; proptosis; and papilledema and glaucoma. The glaucoma may be bilateral; the IOP may increase in the supine position and may decrease in the sitting position. Depending on the duration of the underlying disorder, there may not be any optic nerve deterioration.[108] Malignancy is the underlying basis for this syndrome in 97% of cases.[109] Aortic aneurysms, enlarged hilar nodes, thyroid disease,[5] and inflammatory jugular phlebostenosis[110] have been associated with this entity. Treatment should be aimed at the underlying cause. Miotics have been reported to be effective in lowering the IOP.[111] Aqueous suppressants should also be considered.
CONGESTIVE HEART FAILURE
Congestive heart failure was linked to glaucoma secondary to elevated EVP by Etienne.[112] However, a later report by Bettelheim[113] did not confirm this relationship. Additional clinical studies are needed to elucidate this relationship further.
THROMBOSIS OF CAVERNOUS SINUS OR ORBITAL VEIN
Patients with thrombosis of the cavernous sinus can present with the signs and symptoms of orbital disease previously mentioned: proptosis, involvement of cranial nerves III, IV, V, and VI, as well as signs of obstruction of venous drainage of the cavernous sinus. In addition, there may be retrobulbar pain. Septic cavernous sinus thrombosis may be accompanied by systemic symptoms such as fever, headache, nausea, vomiting, and somnolence. Tolosa-Hunt syndrome is the primary entity to differentiate. Orbital venography can assist in the diagnosis. The correct diagnosis is important because the treatment for thrombosis of the cavernous sinus is heparin therapy, and the therapy for Tolosa-Hunt syndrome is systemic steroids.[114]
VASCULITIS INVOLVING EPISCLERAL VEIN OR ORBITAL VEIN
In patients with either episcleritis or scleritis associated with a variety of systemic diseases such as rheumatoid arthritis, ankylosing spondylitis, erythema nodosum, and tuberculosis, glaucoma was reported in 11.6% of patients with scleritis and in 4% of patients with episcleritis. The cause of glaucoma was related to edema in the aqueous outflow system, peripheral anterior synechiae, or chronic steroids.[115]Patients with chronic inflammatory disease associated with glaucoma are best treated with aqueous suppressants. Low-dose topical steroids should be considered in place of more potent formulations. Laser trabeculoplasty may not be effective in most cases.[116] Finally, filtration surgery may need to be supplemented with antimetabolites to enhance success.[117]
JUGULAR VEIN OBSTRUCTION
The reader is referred to the discussion regarding superior vena cava syndrome.
IDIOPATHIC ELEVATION OF EPISCLERAL VENOUS SYSTEM
In cases that demonstrate no angiographic or radiographic evidence of an underlying cause for elevated EVP, the disease may be considered to be either familial or sporadic. Talusan and associates[118]reported six unilateral cases and one bilateral case in patients with dilated episcleral veins and increased EVP. No evidence of arteriovenous connections could be found angiographically. Two of the patients showed evidence of glaucomatous cupping and field changes, and five demonstrated more cupping in the eye that had the higher EVP. Evidence of idiopathic dilated episcleral vessels and open-angle glaucoma has been documented by others.[119-122] This association should be suspected in individuals with asymmetric IOP and a chronically red eye. As in any patient with elevated EVP, there may be a reflux of blood in Schlemm's canal on gonioscopic examination (Fig. 211.8).
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FIGURE 211.8 Reflux of blood in Schlemm's canal in a patient with idiopathic elevation of episcleral venous pressure. |
SUMMARY
The anatomy, physiology, and methods of measuring EVP were reviewed (Table 211.1). There are three general categories of clinical entities associated with elevated EVP: arteriovenous and venous anomalies, venous obstruction, and idiopathic disease. Topical glaucoma medication and oral carbonic anhydrase inhibitors can be used initially to control IOP. However, the underlying cause must be resolved to achieve long-term stabilization of IOPs. Laser trabeculoplasty can be attempted; however, filtration surgery or seton placement may be needed ultimately in intractable cases to completely bypass the resistance that occurs as a result of elevation in EVP and any primary or secondary changes within the aqueous outflow pathway.
ACKNOWLEDGMENTS
The author wishes to acknowledge Wayne Cornblatt, M.D., for reviewing the manuscript and Nancy Thomas and Nancy Cook for their secretarial assistance.
REFERENCES
1. Lauber H: Anat 1901; 18:437, quoted by Ascher KW.
2. Seidel E: Weitere experimentelle Untersuchungen uber die quelle und den Verlauf der intraokularen Saftsrommung. XX: Uber die Messung des Blutdruckes in dem episcleral Venengeflecht, den vorderen ciliar, und den Wirbelvenen normaler Augen. Graefes Arch Clin Exp Ophthalmol 1923; 112:252.
3. Ascher KW: The aqueous veins: Physiologic importance of the visible elimination of intraocular fluid. Am J Ophthalmol 1942; 25:1174.
4. Ascher KW: Aqueous veins: Preliminary note. Am J Ophthalmol 1942; 25:31.
5. Weinreb RN, Jeng S, Goldstick BJ: Glaucoma secondary to elevated episcleral venous pressure. In: Ritch R, Shields MB, Krupin T, ed. The glaucomas, St Louis: CV Mosby; 1989.
6. Duke-Elder S, Wybar KC: The anatomy of the visual system, St Louis, CV Mosby, 1961.
7. Heyreh SS, Baines JAB: Occlusion of the vortex veins: An experimental study. Br J Ophthalmol 1973; 57:217.
8. Yablonski ME, Podos SM: Glaucoma secondary to elevated episcleral venous pressure. In: Ritch R, Shields MB, ed. The secondary glaucomas, St Louis: CV Mosby; 1982.
9. Anderson DR: Vascular supply to the optic nerve of primates. Am J Ophthalmol 1970; 70:341-351.
10. Weiss DL: Dual origin of glaucoma in encephalotrigeminal haemangiomatosis. Trans Ophthalmol Soc UK 1971; 93:477.
11. Zeimer RC: Episcleral venous pressure. In: Ritch R, Shields MB, Krupin T, ed. The glaucomas, St Louis: CV Mosby; 1989.
12. Brubaker RF: Computer-assisted instruction of current concepts in aqueous humor dynamics. Am J Ophthalmol 1976; 82:59-63.
13. Kupfer C, Sanderson P: Determination of pseudofacility in the eye of man. Arch Ophthalmol 1968; 80:194-196.
14. Brubaker RF: Physiology of aqueous humor formation. In: Drance SM, Neufeld A, ed. Applied pharmacology in the medical treatment of glaucoma, New York: Grune & Stratton; 1984.
15. Maepea O, Bill A: The pressures in the episcleral veins, Schlemm's canal and the trabecular meshwork in monkeys: Effects of changes in intraocular pressure. Exp Eye Res 1989; 49:645-663.
16. Weigelin E, Lohlein H: Blutdruckmessungen an den episkleralen Gefassen des Auges bei kreislaufgesunden Personen. Graefes Arch Clin Exp Ophthalmol 1952; 153:202-213.
17. Friberg TR, Sanborn G, Weinreb RN: Intraocular and episcleral venous pressure increase during inverted posture. Am J Ophthalmol 1987; 103:523-526.
18. Kaskel D, Muller-Breitenkamp R, Williams I, et al: Augeninnendruck, episkleralvenendruck und blutdruck bei anderung der korperlage. Graefes Arch Clin Exp Ophthalmol 1978; 208:217-228.
19. Wilke K: Episcleral venous pressure and pregnancy. Acta Ophthalmol 1975; 125(Suppl):40-41.
20. Talusan ED, Fishbein SL, Schwartz B: Increased pressure of dilated episcleral veins with open-angle glaucoma without exophthalmos. Ophthalmology 1983; 90:257-265.
21. Kupfer C: Clinical significance of pseudofacility. Am J Ophthalmol 1973; 75:193-204.
22. Podos SM, Minas TF, Macr FJ: A new instrument to measure episcleral venous pressure: Comparison of normal eyes and eyes with primary open angle glaucoma. Arch Ophthalmol 1968; 80:209-213.
23. Brubaker R: Determination of episcleral venous pressure in the eye. Arch Ophthalmol 1967; 77:110-114.
24. Gaasterland DE, Pederson JE: Episcleral venous pressure: a comparison of invasive and noninvasive measurements. Invest Ophthalmol Vis Sci 1983; 24:1417-1422.
25. Goldmann H: Eid Kammerwasservenen und das Poiseuille'sche Gesetz. Ophthalmologica 1949; 118:496.
26. Seidel E: Weitere experimentelle Untersuchungen uber die quelle und den verlauf der Intraokularen Saftstromung. XX: Mitteilung uber die Messung des Blutdruckes in dem episcleralen Venengeflecht, den vorderen Ciliarund den Wirbelvenen normaler Augen. Graefes Arch Clin Exp Ophthalmol 1923; 115:112.
27. Zeimer RC, Gieser DK, Wilensky JT, et al: A practical venomanometer: measurement of episcleral venous pressure and assessment of the normal range. Arch Ophthalmol 1983; 101:1447-1449.
28. Krakau CET, Widakowich J, Wilke K: Measurements of the episcleral venous pressure by means of an air jet. Acta Ophthalmol 1973; 51:185-196.
29. Widakowich J: Episcleral venous pressure and flow dynamics. Acta Ophthalmol 1976; 54:500-506.
30. Stepanik J: Neues Verfahren zur Bestimmung des extrokularen episcleralen Venendruckes. Graefes Arch Clin Exp Ophthalmol 1969; 177:116-123.
31. Phelps CD, Thompson HS, Ossoinig KC: The diagnosis and prognosis of atypical carotid-cavernous fistula (red-eyed shunt syndrome). Am J Ophthalmol 1982; 93:423-436.
32. Flanagan JC: Vascular problems of the orbit. Symposium: tumors of the lids and orbit. Ophthalmology 1979; 86:896-913.
33. Miller N: Walsh and Hoyt's clinical neuro-ophthalmology, 4th edn.. Baltimore, Williams & Wilkins, 1988.
34. Jorgensen JS, Guthoff R: Ophthalmoscopic findings in spontaneous carotid-cavernous fistula: an analysis of 20 patients. Graefes Arch Clin Exp Ophthalmol 1988; 226:34-36.
35. Graf CJ: Spontaneous carotid-cavernous fistula: Ehlers-Danlos syndrome and related conditions. Arch Neurol 1965; 13:662.
36. Rios-Montenegro EN, Behrens MM, Hoyt WF: Pseudoxanthoma elasticum: association with bilateral carotid rete mirabile and unilateral carotid-cavernous sinus fistula. Arch Neurol 1972; 26:151-155.
37. Jorgensen JS, Guthoff R: Die Rolle des episkleralen Venendrucks bei der Entstehung von Sekundarglaukomen. Klin Monatsbl Augenheilkd 1988; 193:471-475.
38. Slusher MM, Lennington RB, Weaver RG, et al: Ophthalmic findings in dural arteriovenous shunts. Ophthalmology 1979; 86:720-731.
39. Flaharty PM, Lief WE, Sergott RC, et al: Color Doppler imaging: a new noninvasive technique to diagnose and monitor carotid-cavernous sinus fistulas. Arch Ophthalmol 1991; 109:522-526.
40. Sergott RC, Grossman RI, Savino PJ, et al: The syndrome of paradoxical worsening of dural-cavernous sinus arteriovenous malformation. Ophthalmology 1987; 94:205-212.
41. Solymosi L: Treatment of carotid cavernous fistulas. Klin Monatsbl Augeneilkd 2004.221.
42. Hanneken AM, Miller NR, Debrun GM, et al: Treatment of carotid-cavernous fistulas using a detachable balloon catheter through the superior ophthalmic vein. Arch Ophthalmol 1989; 107:87-92.
43. Wu ZX, Wang ZC: Treatment of traumatic carotid-cavernous fistula with detachable balloon. Chinese Med J 1990; 103:840-845.
44. Barrow DL, Fleisher AS, Hoffman JC: Complications of detachable balloon catheter technique in the treatment of traumatic intracranial arterviovenous fistulas. J Neurosurg 1982; 56:396-403.
45. Fiore PH, Latina MA, Shingleton BJ, et al: The dural shunt syndrome. I. Management of glaucoma. Ophthalmology 1990; 97:56.
46. Guoxiang S, Wenfang T, Dongfang Q: Surgical treatment of orbital varices. Chinese Med J 1979; 92:723.
47. Rathbun JE, Hoyt WF, Beard C: Surgical management of orbitofrontal varix in Klippel-Trenaunay-Weber syndrome. Am J Ophthalmol 1970; 70:109-112.
48. Duke-Elder S, MacFaul PA: System of ophthalmology. The Ocular Adnexa, St Louis, CV Mosby, 1974.
49. Bullock JD, Goldberg SH, Connelly PJ: Orbital varix thrombosis. Ophthalmology 1990; 97:251-256.
50. White JH, Fox AJ, Symons SP: Diagnosis and anatomic mapping of an orbital varix by computed tomographic angiography. Am J Ophthalmol 2005; 140:4945-4947.
51. Winter J, Centeno RS, Bentson JR: Maneuver to aid diagnosis of orbital varix by computed tomography. AJNR 1982; 3:39-40.
52. Jorgensen JS: Ein Ungewohnlicher Fall: Episklerale und orbitale Varizen. Klin Monatsbl Augenheilkd 1987; 191:146-148.
53. Osborn RE, DeWitt JD, Lester PD, et al: Magnetic resonance imaging of an orbital varix with CT and ultrasound correlation. Comput Radiol 1986; 10:155-159.
54. Rosenblum P, Zilkha A: Sudden visual loss secondary to an orbital varix. Surv Ophthalmol 1978; 23:49-56.
55. Lieb WE, Merton DA, Shields JA, et al: Colour Doppler imaging in the demonstration of an orbital varix. Br J Ophthalmol 1990; 74:305-308.
56. McCord CD, Spitalny LA: Localized orbital varices. Arch Ophthalmol 1968; 80:455-460.
57. Golan A, Savir H, Matz S: Intermittent exophthalmos due to orbital varicose vein accompanied by varicose vein of the legs. Ann Ophthalmol 1976; 8:61-64.
58. Takecki A, et al: Embolization for orbital varix. Neuroradiology 1994.36.
59. Handa H, Mori K: Large varix of the superior ophthalmic vein: demonstration by angular phlebography and removal by electrically induced thrombosis: case reports. J Neurosurg 1968; 29:202-205.
60. Salmenson BD, Gelfand YA, Welsh NH, et al: Orbital varix: an unusual cause of proptosis: a case report. S Afr Med J 1988; 74:529-530.
61. Sales MJ, Frise P, Roux FX, et al: Les Varices Orbitaires-A propos d'une observation. Bull Soc Ophtalmol Fr 1989; 11:1287-1291.
62. Kollarits C, Gaasterland D, DiChiro G, et al: Management of a patient with orbital varices, visual loss, and ipsilateral glaucoma. Ophthalmic Surg 1977; 8:54-62.
63. Alexander GL, Norman RM: The Sturge-Weber syndrome, Bristol, England, John Wright & Sons, 1960.
64. Phelps CD: The pathogenesis of glaucoma in Sturge-Weber syndrome. Ophthalmology 1978; 85:276-286.
65. Font RL, Ferry AP: The phakomatoses. Int Ophthalmol Clin 1972; 12:1-50.
66. Miller SJH: Symposium: the Sturge-Weber syndrome. Proc R Soc Med 1963; 56:419.
67. Cibis GW, Tripathi RC, Tripathi BJ: Glaucoma in Sturge-Weber syndrome. Ophthalmology 1984; 91:1061-1071.
68. Sujansky E, Conradi S: Outcome of Sturge-Weber syndrome in 52 adults. Am J Med Genet 1995; 57:35-45.
69. Iwach A, Hoskins HD, Hetherington J, et al: Analysis of surgical and medical management of glaucoma in Sturge-Weber syndrome. Ophthalmology 1990; 97:904-909.
70. Enjolras O, Riche MC, Merland JJ: Facial port-wine stains and Sturge-Weber syndrome. Pediatrics 1985; 76:48-51.
71. Uram M, Zubillaga C: The cutaneous manifestations of Sturge-Weber syndrome. J Clin Neuroopthalmol 1982; 2:245-248.
72. Danis P: Aspects ophtalmologiques des angiomatose du systeme nerveus. Acta Neurol Psychiatr Belg 1950; 50:615-679.
73. Witschel H, Font R: Hemangioma of the choroid: a clinicopathologic study of 71 cases and a review of the literature. Surv Ophthalmol 1976; 20:415-431.
74. Board RJ, Shields MB: Combined trabeculotomy-trabeculectomy for the management of glaucoma associated with Sturge-Weber syndrome. Ophthalmol Surg 1981; 12:813-817.
75. Teekhasaenee C, Ritch R: Glaucoma in phakomatosis pigmentovascularis. Ophthalmology 1997; 104:150-157.
76. Kramer W: Klippel-Trenaunay syndrome. In: Vinken PJ, Bruyn GW, ed. Handbook of clinical neurology. The phakomatoses, New York: Elsevier; 1972.
77. Barkan O: Goniotomy for glaucoma associated with nevus flammeus. Am J Ophthalmol 1957; 43:545-549.
78. O'Brien CS, Porter WC: Glaucoma and nevus flammeus. Arch Ophthalmol 1933; 9:715.
79. Dickens CJ, Hoskins HD: Developmental glaucoma. In: Isenberg SJ, ed. The eye in infancy, Chicago: Year Book Medical; 1989.
80. Mwinula J, Sagawa T, Tawara A, Inomata H: Anterior chamber angle vascularization in Sturge-Weber syndrome. Graefes Arch Clin Exp Ophthalmol 1994; 232:387-391.
81. Akaban N, Hamaka T: Histopathological studyof a case with glaucoma due to Sturge-Weber Syndrome. Jpn J Ophthalmol 2003.47.
82. Baikoff G, Colin J, Bechetoille A, et al: Maladie de Sturge-Weber et glaucome. Bull Soc Ophtalmol Fr 1980; 80:395.
83. Jorgensen JS, Guthoff R: Sturge-Weber-syndrom: Glaukom mit erhohtem episkleralen Venendruck. Klin Monatsbl Augenheilkd 1987; 191:275-278.
84. Spencer WH: Glaucoma. In: Spencer WH, ed. Ophthalmic pathology: an atlas and textbook, 3rd edn.. Philadelphia: WB Saunders; 1985.
85. Shibab ZM, Kristan RW: Recurrent intraoperative choroidal effusion in Sturge-Weber syndrome. J Pediatr Ophthalmol Strabismus 1983; 20:250-252.
86. Theodossiadis G, Damanakis A, Kousandrea CH: Aderhauteffusion wahrend einer antiglaukomatosen Operation bei einem Kind mit Sturge-Weber-Syndrom. Klin Monatsbl Augenheilkd 1985; 186:300-302.
87. Bellows AR, Chylack LT, Epstein DL: Choroidal effusion during glaucoma surgery in patients with prominent episcleral vessels. Arch Opthalmol 1979; 97:493-497.
88. Eibschiz-Tsimhoni M, et al: Assessing the need for posterior sclerotomy at the time of filtering surgery in patient with Sturge-Weber syndrome. Ophthalmology 2003; 110:1361-1363.
89. Ali MA, Fahmy IA, Spaeth GL: Trabeculectomy for glaucoma associated with Sturge-Weber syndrome. Ophthalmic Surg 1990; 21:352-355.
90. Board RJ, Shields MB: Combined trabeculotomy-trabeculectomy for the management of glaucoma associated with Sturge-Weber syndrome. Ophthalmic Surg 1981; 12:813-817.
91. Wagner RS, Caputo AR, Negro RG, et al: Trabeculectomy with cyclocryotherapy for infantile glaucoma in the Sturge-Weber syndrome. Ann Ophthalmol 1988; 20:289-291.
92. Agarwal HC, Sandramouli S, Sihota R, Sood N: Sturge-Weber syndrome: management of glaucoma with combined trabeculotomy-trabeculectomy. Ophthalmic Surg 1993; 24:399-402.
93. Celebi S, Alagoz G, Aykan U: Ocular findings in Sturge-weber syndrome. Eur J Ophthalmol 2000; 10:239-243.
94. Hamush NG, Coleman AL, Wilson MR: Ahmed glaucoma valve implant for management of glaucoma in Sturge-Weber Syndrome. Am J Ophthalmol 1999; 128:758-760.
95. Budenz , et al: Two-staged Baerveldt glaucoma implant for childhood glaucoma associated with Stuge-Weber syndrome. Ophthalmol 2001; 108:2105-2110.
96. Keverline PO, Hiles DA: Trabeculectomy for adolescent onset glaucoma in the Sturge-Weber syndrome. J Pediatr Ophthalmol 1976; 13:144-148.
97. Mandal A, Walton D, John T, Jayagandan A: Mitomycin C-augmented trabeculectomy in refractor congenital glaucoma. Ophthalmology 1997; 104:996-1001.
98. Michelsen WJ, Hilal SK, Stern J: The management of arteriovenous malformations of the orbit. In: Jakobiec FA, ed. Ocular and adnexal tumors, Birmington, AL: Aesculapius; 1978.
99. Howard GM, Jakobiec FA, Michelsen WJ: Orbital arteriovenous malformation with secondary capillary angiomatosis treated by embolization with silastic liquid. Ophthalmology 1983; 90:1136-1139.
100. Murali R, Berenstein A, Hirschfeld A: Intraorbital arteriovenous malformation with spontaneous thrombosis. Ann Ophthalmol 1981; 13:457-459.
101. Levy JV, Zemek L: Ophthalmic arteriovenous malformation. Am J Ophthalmol 1966; 62:971-974.
102. Terry TL, Fred GB: Abnormal arteriovenous communication in the orbit involving the angular vein. Arch Ophthalmol 1938; 19:90.
103. Nordmann PJ, Lobstein A, Gerhard JP: A propos de 14 cas de glaucome par hypertension veineuse d'origine extraoculaire. Ophthalmologica 1961; 142:501.
104. Bietti PGB, Vanni V: Glaucome secondaire à une obstruction veineuse extraoculaire. Ophthalmologica 1961; 142:227-265.
105. Cant JS, Wilson TM: The ocular and orbital circulations in dysthyroid ophthalmopathy. Trans Ophthalmol Soc UK 1974; 94:416-429.
106. Manor RS, Kurz O, Lewitus Z: Intraocular pressure in endocrinological patients with exophthalmos. Ophthalmolgica 1974; 168:241-252.
107. Bouzas AG: The Montgomery lecture, 1980. Endocrine ophthalmopathy. Trans Ophthalmol Soc UK 1980; 100(51):511-520.
108. Alfano JE, Alfano PA: Glaucoma and the superior vena caval obstruction syndrome. Am J Ophthalmol 1956; 42:685-696.
109. Lokich JJ, Goodman R: Superior vena cava syndrome. JAMA 1975; 231:58.
110. Meyer O: Inflammatory jugular phlebostenosis as the cause of glaucoma exogenicum. Br J Ophthalmol 1946; 30:682.
111. Bedrossian EH: Increased intraocular pressure secondary to mediastinal syndrome. Arch Ophthalmol 1952; 47:641-642.
112. Etienne R: Chronic glaucoma and hypertension of the pulmonary artery. Bull Soc Ophtalmol Fr 1957; 70:510-517.
113. Bettelheim H: Der episklerale venendruck bei pulmonaler hypertension. Graefes Arch Clin Exp Ophthalmol 1969; 177:108-115.
114. Brismar G, Brismar J: Aseptic thrombosis of orbital veins and cavernous sinus. Acta Ophthalmol 1977; 55:9-22.
115. Watson PG, Hayreh SS: Scleritis and episcleritis. Br J Ophthalmol 1976; 60:163.
116. Robin AL, Pollack IP: Argon laser trabeculoplasty in secondary forms of open-angle glaucoma. Arch Ophthalmol 1983; 101:382-384.
117. Weinreb RN: Adjusting the dose of 5-fluorouracil after filtration surgery to minimize side effects. Ophthalmology 1987; 94:564-570.
118. Talusan ED, Fishbein SL, Schwartz B: Increased pressure of dilated episcleral veins with open-angle glaucoma without exophthalmos. Ophthalmology 1983; 90:257-265.
119. Radius RL, Maumenee E: Dilated episcleral vessels and open-angle glaucoma. Am J Ophthalmol 1978; 86:31-35.
120. Jorgensen JS, Guthoff R: Zur Genese der einseitig dilatierten episkleralen Gefase und Erhohung des intraokularen Drucks. Klin Monatsbl Augenheilkd 1987; 190:428-430.
121. Bigger JF: Glaucoma with elevated episcleral venous pressure. South Med J 1975; 68:1444-1448.
122. Jorgensen JS, Payer H: Erhohter episkleraler Venendruck bei uvealer effusion. Klin Monatsbl Augenheilkd 1989; 195:14-16.
