SURVEY OF OPHTHALMOLOGY VOLUME 54 NUMBER 5 SEPTEMBER–OCTOBER 2009 MAJOR REVIEW Intraocular Pressure Change in Orbital Disease Muhamed A. Nassr, MBBCh, Carrie L. Morris, MD, Peter A. Netland, MD, PhD, and Zeynel A. Karcioglu, MD Hamilton Eye Institute, Health Sciences Center University of Tennessee, Memphis, Tennessee, USA Abstract. Intraocular pressure change has been found concurrent with many orbital pathologies, particularly those involving proptosis. The objective of this review is to offer an inclusive classification of orbital disease--related intraocular pressure change, not only for oculoplastics and glaucoma specialists, but also for general ophthalmologists. Various orbital conditions associated with increased intraocular pressure and glaucoma are comprehensively summarized, and pathophysiology, clinical manifestations, and treatment options of these diseases are discussed. Graves disease, arterio-venous shunts, trauma, and orbital neoplasia, and other common conditions are discussed in detail; less frequent syndromes such as orbitocraniofacial deformities, phakomatoses, and mucopolysaccharidoses are included for the sake of comprehensiveness, but discussed less extensively. (Surv Ophthalmol 54:519--544, 2009. Ó 2009 Elsevier Inc. All rights reserved.) Key words. Intraocular pressure ocular hypertension glaucoma orbit proptosis I. Introduction (iv) infections and inflammations that change the Changes in intraocular pressure (IOP) are related to anatomy of the orbit and the vascular func- many orbital disorders including hereditary, struc- tion, including cellulitis and other forms of tural, inflammatory, traumatic, and neoplastic dis- orbital inflammation such as Graves disease. eases.69,131,269 These relationships can be described This review covers most of the conditions, disorders, either as causal or associative. There are four and situations in which IOP is elevated due to the primary pathophysiological mechanisms that lead mechanisms listed herein. In addition, a large number to IOP change in orbital disease: of associated pathologies, such as collagen tissue (i) structural abnormalities, including congenital diseases, inborn errors of metabolism, autoimmune and hereditary diseases and disruptions to the disorders, and other pathologies in which the IOP anatomical integrity of the globe and orbital change and proptosis appear to coexist, are discussed. tissues caused by trauma and surgical procedures This latter group of disorders is designated ‘‘associ- (ii) mass effect, which may develop secondary to ated’’because there is no causal relationship in most of neoplasm (rapidly-growing tumor) and/or in- these cases, so the co-occurrence of orbital manifesta- filtrative disease (e.g., leukemia, multiple mye- tions with IOP change is more of a simultaneous loma) compressing ocular and orbital structure presentation. (iii) vascular disease, including arterio-venous mal- In most individuals, there is no bona fide formations and tumor interference in the correlation between the size, location, and type of proper venous drainage of the globe and orbit the compressive orbital lesions and the level of IOP. 519 Ó 2009 by Elsevier Inc. 0039-6257/09/$--see front matter All rights reserved. doi:10.1016/j.survophthal.2009.02.023 520 Surv Ophthalmol 54 (5) September--October 2009 NASSR ET AL Conversely, the flow rate of arterial--venous malfor- aqueous formation [F] in microliters per minute mations is directly correlated with IOP; the faster (mL/mL) divided by facility of outflow [C] in the blood flow from the arterial to venous system, microliters per minute per milliliter of mercury the higher the IOP. Once the flow rate is stabilized, (mL/min/mm Hg). [Po 5 (F/C) þ Pv]. Episcleral however, the IOP ceases to fluctuate. venous pressure is usually constant but may be The secondary ocular manifestations of orbital altered by head position or diseases of the orbit, disease include loss of visual acuity, field and color head, or neck, which may hinder the venous return vision, refractive errors, external eye exposure prob- to the heart and/or shunt the arterial blood into the lems, lid malfunction, extraocular motility distur- venous system. As a result of the lack of valves in bances, conjunctival and retinal vascular changes, orbital veins, venous blood flow is controlled by chorioretinal folds, and optic disc edema and/or pressure gradients. Although acute fluctuations atrophy. None of these clinical features, except the correlate well with changes in episcleral pressure, extraocular muscle problems in some instances of the correlation between IOP changes and chronic Graves disease, is quantitatively correlated with elevated episcleral pressure alterations are more variable. IOP. Also, the individual clinical manifestations that Hence, direct or indirect increased episcleral develop as the result of the displacement of the eye are venous pressure can cause changes in Schlemm’s not always directly correlated to the degree and the type canal, thereby raising IOP. Examples of this physio- of proptosis. For example, there is no clear relationship pathological mechanism that lead to high IOP between the size of a space-occupying lesion in the orbit include nevus flammeus, thyroid ophthalmopathy, and the extent and direction of the chorioretinal folds. space-occupying orbital lesions, and carotid-cavern- Congestion and increased tortuosity of conjunctival ous or dural AV fistulas. In these situations, blood and retinal veins generally occur with masses located in can sometimes be seen in Schlemm’s canal, since midorbit, causing stasis through the vortex veins. the aqueous humor drains from Schlemm’s canal Contrary to what might be expected, the severity of into episcleral veins via endothelial-lined outlet these changes which is best judged clinically with aqueducts. flourescein angiography, does not correlate directly For example, a small comparative study124 pro- with the degree of proptosis and/or the level of IOP. posed that modified ophthalmodynamometry dem- Disk edema and optociliary shunt vessels are other onstrated an increase in central retinal vein colla conditions that deserve particular attention in a prop- pse-pressure in patients with dilated episcleral veins totic eye.132,265 Optociliary vessels are venous shunts and, subsequently, an increase in IOP. The authors that develop between the retinal vasculature and the postulated that modified ophthalmodynamometry juxtapapillary choroidal circulation when the retinal has a role in the diagnosis of secondary glaucoma and venous return in the central retina vein is blocked. disease processes associated with dilated episcleral However,thepresenceofretinochoroidalvenousshunt veins. vessels does not necessarily cause a rise in IOP, because they primarily involve the retinal vasculature.121 B. VENOUS VASCULATURE OF THE ORBIT II. Anatomical Relationship between the Most venous drainage from the orbit occurs Vasculature of the Globe and the Orbit through the superior and inferior ophthalmic veins, which ultimately feed into the cavernous sinus. In To understand the complex relationship between contrast to the arterial system, the venous system has IOP and the globe’s position in the orbit in different a significant amount of variability in its classifica- types of ocular and adnexal pathology, one must tion, distribution, arrangement, amount, and tra- evaluate the anatomy as well as the embryology of the jectory. The tributaries of medial palpebral, superior orbital vascular network and its impact on eye vortex, lacrimal, muscular, central retinal, anterior pressure (Figs. 1 and 2). The episcleral venous system ethmoidal, and inferior ophthalmic veins drain into mainly empties into the anterior ciliary and superior the superior ophthalmic vein. ophthalmic veins, eventually draining into the cav- 167 The angular, nasofrontal, supratrochlear, and ernous sinus. Thus, any disease process that affects supraorbital veins converge posteriorly to form the this drainage pathway as a result of structural, superior ophthalmic vein, which has three divisions. occlusive, compressive, or destructive physiopathol- The first (anterior) segment, formed by the conver- ogy may alter the IOP. gence of the angular and supraorbital veins, drains posterolaterally and lies next to the trochlea on A. EPISCLERAL VENOUS PRESSURE the inferomedial side of the superior rectus muscle. According to the Goldmann equation, IOP [Po] The second section of the vein runs underneath the equals episcleral venous pressure [Pv] plus rate of superior rectus muscle within the muscle cone and IOP CHANGE IN ORBITAL DISEASE 521 Fig. 1. Axial view of anatomical drawings of orbital vasculature. ACV 5 anterior collateral vein; AEC 5 anterior ethmoidal cells; AFV 5 anterior facial vein; AV 5 angular vein; CA 5 carotid artery; CRV 5 central retinal vein; CVS 5 cavernous sinus; ICV 5 intermediate collateral vein; IFOV 5 inferior ophthalmic vein; IPAV 5 inferior palpebral vein; IVP 5 infraorbital venous plexus; LV 5 lacrimal vein; MCV 5 medial collateral vein; MEC 5 middle ethmoidal cell; MOV 5 medial ophthalmic vein; PEC 5 posterior ethmoidal cell; PTP 5 pterygoid plexus; SOV 5 superior ophthalmic vein; VV 5 vortex vein. annulus of Zinn. The vein assumes a lateral trajec- pass takes place along the temporal border of the tory at the midorbit posterior to the globe, receiving superior rectus muscle outside the annulus of Zinn. outflow from the superior medial and lateral vortex Some anatomy texts describe anterior, medial, veins and the superior