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Orbital computed tomographic characteristics of globe subluxation in thyroid orbitopathy
Orbital Computed Tomographic Characteristics of Globe Subluxation in Thyroid Orbitopathy Peter A. D. Rubin, MD, Lynnette M. Watkins, MD, Shimon Rumelt, MD, Francis C. Sutula, MD, Richard L. Dallow, MD Objective: Axial globe subluxation may complicate thyroid orbitopathy. This acute event is defined by anterior displacement of the globe equator beyond the orbital rim, lid retraction behind the equator, and tethering of the optic nerve. The authors explored the factors leading to spontaneous globe subluxation in patients with thyroid orbitopathy. Design: A clinical review. Main Outcome Measures: The medical charts and axial and coronal orbital computed tomographic (CT) scans of all the patients with spontaneous globe subluxation were reviewed. The patients were categorized according to their CT scans into type I (“lipogenic” variant) or type II (“myogenic” variant). Results: Four (0.1%) of approximately 4000 patients with thyroid orbitopathy presented with spontaneous globe subluxation. All of these patients had increased orbital fat without significant enlargement of the extraocular muscles. Thus, they represent type-I thyroid orbitopathy. Conclusions: Globe subluxation in thyroid orbitopathy requires compliance of the orbital soft tissues and extensibility of the extraocular muscles. These are characteristics of type-I orbitopathy. The increased fat content results in more compliance of the soft tissues, and the normal caliber of the muscles allows them to become more extensible. This permits the acute contraction of the eyelids posterior to the equator of the globe. Patients with type-I orbitopathy and extensive proptosis may be at relatively greater risk of having globe subluxation develop. Ophthalmology 1998;105:2061–2064 Globe subluxation is defined as an acute event of anterior displacement of the globe, displacement of the equator anterior to the orbital rim, and eyelid retraction posterior to the equator of the globe. The axial subluxation of the globe is usually seen in patients with advanced thyroid orbitopathy. It may also occur in the setting of space occupying lesions such as orbital tumors, cysts, hemorrhage, congenital malformations, trauma, shallow bony orbits, as well as iatrogenic causes.1 Globe subluxation may occur spontaneously or may be induced during ophthalmic examination, when the upper eyelid is elevated and retracted against the superior orbital rim. Acute spontaneous globe subluxation may be the presenting sign of thyroid orbitopathy, and when it occurs it is
Originally received: March 9, 1998. Revision accepted: June 2, 1998. Manuscript no. 98123. From Ophthalmic Plastics, Orbital, and Cosmetic Eyelid Surgery, Department of Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston, Massachusetts. Presented in part at the Association for Research and Vision in Ophthalmology annual meeting, Fort Lauderdale, Florida, May, 1997. Supported in part by Dr. Gideon Manelis Award, Israel Medical Association–World Fellowship (SR). Reprint requests to Peter A. D. Rubin, MD, Ophthalmic Plastics and Orbital Surgery, Massachusetts Eye & Ear Infirmary, 243 Charles Street, Boston, MA 02114.
an alarming situation for the patient. However, it has not gained attention in the ophthalmic literature, probably because of the rarity of this manifestation. We attempted to characterize the orbital computed tomographs (CT) of patients with globe subluxation to examine our postulation that patients with relatively normal extraocular musculature and excessive intraorbital fat are more prone to have this disorder develop.
Results Of approximately 4000 patients with thyroid orbitopathy seen in our practices, 4 patients presented with spontaneous subluxation of the globe. All patients with globe subluxation had increased orbital fat without significant enlargement of the extraocular musculature on orbital CT. None had a history of diplopia on presentation or during the course of their disease. They had no evidence of orbital inflammation on examination. Three of the patients were female, and the mean age was 36 years.
Case Reports Case 1. A 40-year-old white woman with an 18-month history of Graves’ disease presented with a chief complaint that her eyes “keep popping out.” The patient previously was treated with sub-
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Ophthalmology Volume 105, Number 11, November 1998
Figure 1. Case 2. Side view of globe subluxation. Note the extreme retraction of the eyelids posterior to the equator of the globe.
total thyroidectomy and radioactive iodine and later with thyroid supplements. On examination, her visual acuity was 20/20 in each eye. Exophthalmometry measured 26 mm in the right eye and 25.5 mm in the left eye (base, 102 mm). Four millimeters of superior and inferior scleral show, and 4 mm of lagophthalmos were noted. The ocular motility was normal without diplopia. Visual fields were normal in each eye, and the optic nerves appeared normal. No other pathologic findings were noted. Orbital CT showed bilateral proptosis with increased orbital fat and slight bilateral and symmetric prominence of the inferior and medial rectus muscles. The patient underwent transantral orbital decompression of the orbital floor in each eye, after which her symptoms resolved. Her exophthalmos decreased by 4 mm in the right eye and 3 mm in the left eye, and the patient maintained normal ocular alignment and motility. Case 2. A 36-year-old white woman presented to the emergency department reporting that her right eye protruded from the eye socket 1 hour before presentation. The patient repositioned the globe by pressing the eyelids axially. However, she noted a decrease in visual acuity after this event. The patient had an 8-year history of Graves’ disease and bilateral proptosis without diplopia. She had been treated with thyroidectomy followed by supplemental thyroxine therapy. On acute presentation, her best-corrected visual acuity was 20/100 in the right eye and 20/20 in the left eye. There was an afferent pupillary defect noted in the right eye and decreased color vision (1⁄9 Ishihara color plates). Exophthalmometry was 25 mm in the right eye and 22 mm in the left eye with a base of 97 mm. The ocular motility was normal. Lagophthalmos of 3 mm in the right eye and 1 mm in the left eye was noted. Results from slit-lamp examination were remarkable only for bilateral superficial punctate keratopathy. No signs of optic disc swelling or pallor were noted. The subluxation was induced by manual retraction of the eyelids (Fig 1). After treatment with intravenous methylprednisolone (100 mg), the patient’s color discrimination improved. She was able to identify four of eight Ishihara plates. Her visual acuity improved to 20/40 in the right eye. There was resolution of the afferent pupillary defect in the right eye. Orbital CT showed increased volume of the orbital fat, displac-
2062
ing the right globe anteriorly and tethering the optic nerves (Figs 2A,B). The patient underwent transantral orbital decompression of the floor and medial wall in the right eye. On subsequent examinations, the exophthalmos decreased by 4 mm and the visual acuity improved to 20/30. Case 3. A 37-year-old white woman presented with a chief complaint of more than 30 episodes of spontaneous globe subluxation, facilitated by touching or rubbing her eyelids. She had a 20-year history of Graves’ orbitopathy and had undergone bilateral upper eyelid recession for lid retraction. There was no history of diplopia. The patient had corrected visual acuity of 20/20 in each eye on presentation. Her extraocular motility was normal without diplopia. Eyelid retraction in each eye was present with 5 mm of upper and lower scleral show and “flare” of the lateral upper lids. Exophthalmometry was 35 mm in each eye (base, 109 mm). The ocular examination was otherwise normal. Orbital CT showed increased orbital fat with normal cross-section diameter of the extraocular muscles. The globes appeared tethered and the optic nerves stretched. The patient underwent medial wall and orbital floor decompression in the right eye and medial wall, lateral wall, and orbital floor decompression in the left eye with advancement of the lateral wall in the left eye. After surgery, the globe subluxation resolved and the exophthalmos decreased by 7 mm in the right eye and 9 mm in the left eye. Ocular alignment and motility were preserved. Case 4. A 30-year-old white man with a 5-year history of Graves’ orbitopathy presented for evaluation after an acute spontaneous globe subluxation in the left eye while playing baseball.
Figure 2. Case 2. Coronal (A) and axial (B) orbital computed tomographic views showing marked proptosis attributed to the increased orbital fat volume without enlargement of the extraocular muscles.
Rubin et al 䡠 Globe Subluxation in Thyroid Orbitopathy He repositioned the globe before arrival in the emergency department. He had no diplopia. Visual acuity was 20/20 in each eye, and exophthalmometry was 30 mm in each eye. There was no evidence of exposure keratopathy or optic neuropathy. Orbital CT showed bilateral proptosis with increased orbital fat and minimal infiltration and enlargement of the extraocular musculature. The patient underwent successful lateral wall and medial orbital floor decompression with resolution of the globe subluxation.
Discussion Two clinical subtypes of thyroid orbitopathy have been described by Nunery.2 Patients with type-I orbitopathy usually have normal ocular motility or may have only minimal limitation of ductions in extreme gaze position. Type-I patients present with variable degrees of symmetric proptosis and absence of orbital inflammatory signs. These patients tend to be young women (mean age, 36 years, with a female-to-male ratio of 8:1). The orbital CT scans of these patients show increased volume of orbital fat with or without minimal enlargement of the extraocular muscles. Type-II orbitopathy is the “restrictive myopathy” variant. Patients with this type of orbitopathy have diplopia within 20° of primary position and asymmetric proptosis. The mean age of this group of patients is 52 years, and the female-to-male ratio is 2:1. Orbital CT shows asymmetric enlargement of the extraocular muscles and normal fat content (Fig 3A). In our clinical experience, the majority of patients with prominent proptosis (⬎24 mm) have enlarged extraocular muscles seen on CT. Thus, the cases presented here represent a minority of patients in whom expanded fat volume alone accounts for the clinical exophthalmos. All four patients with spontaneous globe subluxation due to thyroid-related orbitopathy showed increased orbital fat without significant enlargement of the extraocular muscles. Thus, they represent type-I orbitopathy. The patients’ age and gender also reflect type-I orbitopathy group. We suggest that globe subluxation in thyroid orbitopathy requires compliance of soft tissues and extensibility of the extraocular muscles. An increase in retrobulbar orbital fat causes anterior displacement of the globe and axial subluxation (Fig 3B). When the extraocular muscles are not enlarged, they do not limit the anterior displacement of the globe. Imbalance between the increased volume of the retrobulbar fat and the enlargement of the extraocular muscles may result in globe subluxation. We suggest that with more significant muscle enlargement, subluxation may occur only with manipulations of the upper eyelid. In myogenic orbitopathy, infiltration and enlargement of the extraocular muscles may limit the anterior movement of the globe as well as contraction of the eyelids posterior to the globe, both requirements for globe subluxation (Fig 3B). Another barrier against globe subluxation is the upper eyelid due to the tarsal and canthal tendon support. In thyroid orbitopathy, this barrier for axial displacement may be weakened by the retraction of the eyelid. When subluxation occurs, the eyelids retract further, posterior to the equator of the globe. This situation represents the most extreme degree of eyelid retraction. Other factors that may
Figure 3. A, schematic diagram of type-II thyroid orbitopathy. Note the significant enlargement of the extraocular muscles, which serve to limit anterior displacement of the globe. B, schematic diagram of axial globe subluxation in type-I thyroid orbitopathy. Because the muscles are not enlarged, they are more freely extensible. This, combined with the large amount of orbital fat relative to the musculature, allows the eye to subluxate.
facilitate globe subluxation in patients with exophthalmos are shallow bony orbits and short axial length of the globe. In these two situations, the equator of the globe is in greater proximity to the orbital rim and is relatively easy to dislocate. Thus, globe subluxation is determined by four factors: (1) enlargement of retrobulbar fat; (2) compliance of the extraocular muscles; (3) the eyelid barrier; and (4) the size of the orbits and the globes. Spontaneous globe subluxation occurred in all four patients after the diagnosis of Graves’ disease. The interval between the diagnosis of Graves’ disease and this manifestation was 1.5 to 20 years (mean, 8.6 years). Previous studies showed that thyroid-related orbitopathy may precede, occur concurrently, or occur after Graves’ thyroid disease.3,4 These few cases suggest that globe subluxation is a late manifestation relative to the diagnosis of Graves’ disease. Furthermore, in a recent large cohort study, globe subluxation has not been reported as an initial sign for thyroid orbitopathy.5 The interval between the diagnosis of Graves’ disease or thyroid orbitopathy permits follow-up examinations and proper timing of surgical intervention. Although globe subluxation is a dreadful event to the patient, initiating emergent medical attention, it may be devastating if left untreated. The length of the intraorbital segment of the optic nerve is approximately 25 mm while
2063
Ophthalmology Volume 105, Number 11, November 1998 the distance of the posterior pole of the globe from the orbital apex is 18 mm. This allows stretching of the optic nerve up to 7 mm if proptosis occurs. The normal position of the globe equator is approximately 10 mm posterior to the inferior orbital rim, where the orbital circumference is the largest. In subluxation, axial displacement of the globe of more than 10 mm causes tethering of the optic nerve and tenting of the globe (Fig 3B). In this situation, vision is acutely threatened by optic neuropathy and exposure keratopathy. Therefore, it is important to carefully monitor patients with type-I orbitopathy who show extensive proptosis or rapid progression of exophthalmos. Recognition of this rare manifestation of thyroid orbitopathy is essential. The patient should be instructed regarding the nature of this phenomenon and the probability of recurrent episodes until more definitive treatment is used. The acute episode of subluxation can be treated effectively with manual repositioning of the globe with axial pressure and adjunctive use of steroids if there is any sign of an acute optic neuropathy. Tarsorrhaphy may be performed at presentation as a temporary measure to prevent additional episodes of subluxa-
2064
tion. Orbital bony decompression is the definitive treatment of choice for these patients, since it results in orbital expansion and reduction of proptosis and it minimizes the recurrence of globe subluxation.
References 1. Duke–Elder S. System of Ophthalmology. Vol. 13. London: Henry Kimpton, 1974;1233– 4. 2. Nunery WR. Ophthalmic Graves’ disease: a dual theory of pathogenesis. Ophthalmol Clin North Am 1991;4:73– 87. 3. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 1993;14:747–93. 4. Bartley GB, Fatourechi V, Kadrmas EF, et al. The chronology of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996;121:426 –34. 5. Bartley GB, Fatourechi V, Kadrmas EF, et al. Clinical features of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996;121:284 –90.
Originally received: March 9, 1998. Revision accepted: June 2, 1998. Manuscript no. 98123. From Ophthalmic Plastics, Orbital, and Cosmetic Eyelid Surgery, Department of Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston, Massachusetts. Presented in part at the Association for Research and Vision in Ophthalmology annual meeting, Fort Lauderdale, Florida, May, 1997. Supported in part by Dr. Gideon Manelis Award, Israel Medical Association–World Fellowship (SR). Reprint requests to Peter A. D. Rubin, MD, Ophthalmic Plastics and Orbital Surgery, Massachusetts Eye & Ear Infirmary, 243 Charles Street, Boston, MA 02114.
an alarming situation for the patient. However, it has not gained attention in the ophthalmic literature, probably because of the rarity of this manifestation. We attempted to characterize the orbital computed tomographs (CT) of patients with globe subluxation to examine our postulation that patients with relatively normal extraocular musculature and excessive intraorbital fat are more prone to have this disorder develop.
Results Of approximately 4000 patients with thyroid orbitopathy seen in our practices, 4 patients presented with spontaneous subluxation of the globe. All patients with globe subluxation had increased orbital fat without significant enlargement of the extraocular musculature on orbital CT. None had a history of diplopia on presentation or during the course of their disease. They had no evidence of orbital inflammation on examination. Three of the patients were female, and the mean age was 36 years.
Case Reports Case 1. A 40-year-old white woman with an 18-month history of Graves’ disease presented with a chief complaint that her eyes “keep popping out.” The patient previously was treated with sub-
2061
Ophthalmology Volume 105, Number 11, November 1998
Figure 1. Case 2. Side view of globe subluxation. Note the extreme retraction of the eyelids posterior to the equator of the globe.
total thyroidectomy and radioactive iodine and later with thyroid supplements. On examination, her visual acuity was 20/20 in each eye. Exophthalmometry measured 26 mm in the right eye and 25.5 mm in the left eye (base, 102 mm). Four millimeters of superior and inferior scleral show, and 4 mm of lagophthalmos were noted. The ocular motility was normal without diplopia. Visual fields were normal in each eye, and the optic nerves appeared normal. No other pathologic findings were noted. Orbital CT showed bilateral proptosis with increased orbital fat and slight bilateral and symmetric prominence of the inferior and medial rectus muscles. The patient underwent transantral orbital decompression of the orbital floor in each eye, after which her symptoms resolved. Her exophthalmos decreased by 4 mm in the right eye and 3 mm in the left eye, and the patient maintained normal ocular alignment and motility. Case 2. A 36-year-old white woman presented to the emergency department reporting that her right eye protruded from the eye socket 1 hour before presentation. The patient repositioned the globe by pressing the eyelids axially. However, she noted a decrease in visual acuity after this event. The patient had an 8-year history of Graves’ disease and bilateral proptosis without diplopia. She had been treated with thyroidectomy followed by supplemental thyroxine therapy. On acute presentation, her best-corrected visual acuity was 20/100 in the right eye and 20/20 in the left eye. There was an afferent pupillary defect noted in the right eye and decreased color vision (1⁄9 Ishihara color plates). Exophthalmometry was 25 mm in the right eye and 22 mm in the left eye with a base of 97 mm. The ocular motility was normal. Lagophthalmos of 3 mm in the right eye and 1 mm in the left eye was noted. Results from slit-lamp examination were remarkable only for bilateral superficial punctate keratopathy. No signs of optic disc swelling or pallor were noted. The subluxation was induced by manual retraction of the eyelids (Fig 1). After treatment with intravenous methylprednisolone (100 mg), the patient’s color discrimination improved. She was able to identify four of eight Ishihara plates. Her visual acuity improved to 20/40 in the right eye. There was resolution of the afferent pupillary defect in the right eye. Orbital CT showed increased volume of the orbital fat, displac-
2062
ing the right globe anteriorly and tethering the optic nerves (Figs 2A,B). The patient underwent transantral orbital decompression of the floor and medial wall in the right eye. On subsequent examinations, the exophthalmos decreased by 4 mm and the visual acuity improved to 20/30. Case 3. A 37-year-old white woman presented with a chief complaint of more than 30 episodes of spontaneous globe subluxation, facilitated by touching or rubbing her eyelids. She had a 20-year history of Graves’ orbitopathy and had undergone bilateral upper eyelid recession for lid retraction. There was no history of diplopia. The patient had corrected visual acuity of 20/20 in each eye on presentation. Her extraocular motility was normal without diplopia. Eyelid retraction in each eye was present with 5 mm of upper and lower scleral show and “flare” of the lateral upper lids. Exophthalmometry was 35 mm in each eye (base, 109 mm). The ocular examination was otherwise normal. Orbital CT showed increased orbital fat with normal cross-section diameter of the extraocular muscles. The globes appeared tethered and the optic nerves stretched. The patient underwent medial wall and orbital floor decompression in the right eye and medial wall, lateral wall, and orbital floor decompression in the left eye with advancement of the lateral wall in the left eye. After surgery, the globe subluxation resolved and the exophthalmos decreased by 7 mm in the right eye and 9 mm in the left eye. Ocular alignment and motility were preserved. Case 4. A 30-year-old white man with a 5-year history of Graves’ orbitopathy presented for evaluation after an acute spontaneous globe subluxation in the left eye while playing baseball.
Figure 2. Case 2. Coronal (A) and axial (B) orbital computed tomographic views showing marked proptosis attributed to the increased orbital fat volume without enlargement of the extraocular muscles.
Rubin et al 䡠 Globe Subluxation in Thyroid Orbitopathy He repositioned the globe before arrival in the emergency department. He had no diplopia. Visual acuity was 20/20 in each eye, and exophthalmometry was 30 mm in each eye. There was no evidence of exposure keratopathy or optic neuropathy. Orbital CT showed bilateral proptosis with increased orbital fat and minimal infiltration and enlargement of the extraocular musculature. The patient underwent successful lateral wall and medial orbital floor decompression with resolution of the globe subluxation.
Discussion Two clinical subtypes of thyroid orbitopathy have been described by Nunery.2 Patients with type-I orbitopathy usually have normal ocular motility or may have only minimal limitation of ductions in extreme gaze position. Type-I patients present with variable degrees of symmetric proptosis and absence of orbital inflammatory signs. These patients tend to be young women (mean age, 36 years, with a female-to-male ratio of 8:1). The orbital CT scans of these patients show increased volume of orbital fat with or without minimal enlargement of the extraocular muscles. Type-II orbitopathy is the “restrictive myopathy” variant. Patients with this type of orbitopathy have diplopia within 20° of primary position and asymmetric proptosis. The mean age of this group of patients is 52 years, and the female-to-male ratio is 2:1. Orbital CT shows asymmetric enlargement of the extraocular muscles and normal fat content (Fig 3A). In our clinical experience, the majority of patients with prominent proptosis (⬎24 mm) have enlarged extraocular muscles seen on CT. Thus, the cases presented here represent a minority of patients in whom expanded fat volume alone accounts for the clinical exophthalmos. All four patients with spontaneous globe subluxation due to thyroid-related orbitopathy showed increased orbital fat without significant enlargement of the extraocular muscles. Thus, they represent type-I orbitopathy. The patients’ age and gender also reflect type-I orbitopathy group. We suggest that globe subluxation in thyroid orbitopathy requires compliance of soft tissues and extensibility of the extraocular muscles. An increase in retrobulbar orbital fat causes anterior displacement of the globe and axial subluxation (Fig 3B). When the extraocular muscles are not enlarged, they do not limit the anterior displacement of the globe. Imbalance between the increased volume of the retrobulbar fat and the enlargement of the extraocular muscles may result in globe subluxation. We suggest that with more significant muscle enlargement, subluxation may occur only with manipulations of the upper eyelid. In myogenic orbitopathy, infiltration and enlargement of the extraocular muscles may limit the anterior movement of the globe as well as contraction of the eyelids posterior to the globe, both requirements for globe subluxation (Fig 3B). Another barrier against globe subluxation is the upper eyelid due to the tarsal and canthal tendon support. In thyroid orbitopathy, this barrier for axial displacement may be weakened by the retraction of the eyelid. When subluxation occurs, the eyelids retract further, posterior to the equator of the globe. This situation represents the most extreme degree of eyelid retraction. Other factors that may
Figure 3. A, schematic diagram of type-II thyroid orbitopathy. Note the significant enlargement of the extraocular muscles, which serve to limit anterior displacement of the globe. B, schematic diagram of axial globe subluxation in type-I thyroid orbitopathy. Because the muscles are not enlarged, they are more freely extensible. This, combined with the large amount of orbital fat relative to the musculature, allows the eye to subluxate.
facilitate globe subluxation in patients with exophthalmos are shallow bony orbits and short axial length of the globe. In these two situations, the equator of the globe is in greater proximity to the orbital rim and is relatively easy to dislocate. Thus, globe subluxation is determined by four factors: (1) enlargement of retrobulbar fat; (2) compliance of the extraocular muscles; (3) the eyelid barrier; and (4) the size of the orbits and the globes. Spontaneous globe subluxation occurred in all four patients after the diagnosis of Graves’ disease. The interval between the diagnosis of Graves’ disease and this manifestation was 1.5 to 20 years (mean, 8.6 years). Previous studies showed that thyroid-related orbitopathy may precede, occur concurrently, or occur after Graves’ thyroid disease.3,4 These few cases suggest that globe subluxation is a late manifestation relative to the diagnosis of Graves’ disease. Furthermore, in a recent large cohort study, globe subluxation has not been reported as an initial sign for thyroid orbitopathy.5 The interval between the diagnosis of Graves’ disease or thyroid orbitopathy permits follow-up examinations and proper timing of surgical intervention. Although globe subluxation is a dreadful event to the patient, initiating emergent medical attention, it may be devastating if left untreated. The length of the intraorbital segment of the optic nerve is approximately 25 mm while
2063
Ophthalmology Volume 105, Number 11, November 1998 the distance of the posterior pole of the globe from the orbital apex is 18 mm. This allows stretching of the optic nerve up to 7 mm if proptosis occurs. The normal position of the globe equator is approximately 10 mm posterior to the inferior orbital rim, where the orbital circumference is the largest. In subluxation, axial displacement of the globe of more than 10 mm causes tethering of the optic nerve and tenting of the globe (Fig 3B). In this situation, vision is acutely threatened by optic neuropathy and exposure keratopathy. Therefore, it is important to carefully monitor patients with type-I orbitopathy who show extensive proptosis or rapid progression of exophthalmos. Recognition of this rare manifestation of thyroid orbitopathy is essential. The patient should be instructed regarding the nature of this phenomenon and the probability of recurrent episodes until more definitive treatment is used. The acute episode of subluxation can be treated effectively with manual repositioning of the globe with axial pressure and adjunctive use of steroids if there is any sign of an acute optic neuropathy. Tarsorrhaphy may be performed at presentation as a temporary measure to prevent additional episodes of subluxa-
2064
tion. Orbital bony decompression is the definitive treatment of choice for these patients, since it results in orbital expansion and reduction of proptosis and it minimizes the recurrence of globe subluxation.
References 1. Duke–Elder S. System of Ophthalmology. Vol. 13. London: Henry Kimpton, 1974;1233– 4. 2. Nunery WR. Ophthalmic Graves’ disease: a dual theory of pathogenesis. Ophthalmol Clin North Am 1991;4:73– 87. 3. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 1993;14:747–93. 4. Bartley GB, Fatourechi V, Kadrmas EF, et al. The chronology of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996;121:426 –34. 5. Bartley GB, Fatourechi V, Kadrmas EF, et al. Clinical features of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996;121:284 –90.