eMedicine Specialties > Ophthalmology > Intraocular Pressure
Glaucoma, Unilateral
Updated: Mar 8, 2007
Introduction
Background
While any type of glaucoma can be unilateral, primary open-angle glaucoma, primary angle-closure glaucoma, primary infantile glaucoma, juvenile-onset glaucoma, and pigmentary glaucoma are generally bilateral diseases, the severity of which may be asymmetric in the two eyes.
This article reviews glaucoma associated with increased episcleral venous pressure (EVP) and glaucoma associated with iridocorneal endothelial (ICE) syndrome.
Several etiologies of unilateral glaucoma are discussed in detail in other articles, including Glaucoma, Pseudoexfoliation; Glaucoma, Uveitic; Glaucoma, Lens-Particle; Glaucoma, Drug-Induced; Glaucoma, Neovascular; Glaucoma, Intraocular Tumors; Glaucoma, Hyphema; Glaucoma, Angle Recession; and Glaucoma, Malignant.
Pathophysiology
Increased EVP
In the early 1900s, Lauber provided histological evidence that the canal of Schlemm was connected to the episcleral venous network. Aqueous humor drains via the anterior surface of the ciliary body or through the trabecular meshwork, Schlemm canal, collector channels, and, subsequently, aqueous veins. These pathways have been termed unconventional and conventional, respectively.
While the unconventional pathway is independent of pressure, outflow via the conventional route is passive and depends largely on the difference between the intraocular pressure (IOP) and EVP; as EVP increases relative to IOP, or as resistance increases, flow decreases.
The 3 general pathophysiological mechanisms of increased EVP are arteriovenous anomalies, venous obstruction, and idiopathic. Arteriovenous anomalies associated with increased EVP include carotid-cavernous sinus fistula, orbital varix, Sturge-Weber syndrome, orbital-meningeal shunts, carotid-jugular venous shunts, and intraocular vascular shunts. Venous obstruction may be caused by a retrobulbar tumor, thyroid ophthalmopathy, superior vena cava syndrome, congestive heart failure, thrombosis of the cavernous sinus or orbital vein, vasculitis involving the episcleral or orbital vein, and jugular vein obstruction.
ICE syndrome
The pathophysiological mechanism underlying ICE syndrome remains unknown. However, the finding of chronic inflammatory cells in the corneal specimens of patients with ICE syndrome suggests a viral etiology. In a study using polymerase chain reaction techniques, 16 of 25 corneas from patients with ICE syndrome and 4 of 6 patients with herpetic keratitis were positive for herpes simplex virus.
Glaucoma associated with ICE syndrome is believed to be due to trabecular meshwork obstruction caused by peripheral anterior synechiae or, less commonly, an abnormal cellular membrane.
Frequency
United States
The frequency of glaucoma associated with increased EVP or with ICE syndrome is unknown.
Glaucoma has been reported to occur in 30% of patients with Sturge-Weber syndrome, 5% of patients with thyroid ophthalmopathy, 11.6% of patients with scleritis, and 4% of patients with episcleritis.
Mortality/Morbidity
- Glaucoma is the third leading cause of blindness in the United States.
- Because glaucoma may progress insidiously without causing symptoms, progressive glaucomatous damage may occur without the patient even being aware of the diagnosis.
- Prompt and continued control of IOP can prevent ocular damage due to glaucoma.
Sex
- Traumatic carotid-cavernous sinus fistulae occur more commonly in males than in females.
- ICE syndrome occurs more commonly in females than in males.
Age
- Spontaneous carotid-cavernous sinus fistulae typically occur in middle-aged to elderly individuals, while traumatic carotid-cavernous sinus fistulae occur most commonly in young persons.
- It has been reported that 60% of patients with glaucoma associated with Sturge-Weber syndrome acquire glaucoma before age 2 years, and the remaining patients develop glaucoma later in childhood or in early adulthood.
- The onset of ICE syndrome generally occurs in early to middle adulthood.
Clinical
History
- Elicit history of trauma, thyroid disease, congestive heart failure, vasculitis, malignancy, and other systemic diseases.
- Diplopia may be a presenting complaint of patients with a carotid-cavernous sinus fistula, thyroid ophthalmopathy, or retrobulbar tumor.
- Carotid-cavernous sinus fistulae often present after the following:
- A severe head injury
- Any penetrating injury to the orbit injuring the medial or inferomedial wall of the orbit and/or the superior orbital fissure
- Surgery involving the internal carotid artery
- Rupture of a preexisting aneurysm of the internal carotid artery
Physical
- Ophthalmic examination
- Increased EVP may cause pulsating exophthalmos, conjunctival chemosis, engorgement of the episcleral vein, restricted ocular motility, ocular bruit, and ocular ischemia.
- Dilated episcleral vessels are a prominent feature of Sturge-Weber syndrome; choroidal hemangioma is present in 31-50% of patients with Sturge-Weber syndrome.
- A common clinical sign of an orbital varix is intermittent exophthalmos (exophthalmos occurring when the head is placed in a dependent position, when the patient sneezes, or when the patient performs a Valsalva maneuver).
- Orbital tumors may cause proptosis and restricted ocular motility.
- Thyroid ophthalmopathy may cause proptosis, restricted ocular motility, conjunctival chemosis, epiphora, exposure keratitis, and optic nerve compression.
- Presenting signs of the superior vena cava syndrome include edema of the lid, face, and conjunctiva; vascular engorgement of the fundus, episclera, and conjunctiva; proptosis; optic nerve edema; and glaucoma.
- IOP may increase while supine and may decrease while sitting.
- The most common presenting manifestations of ICE syndrome are iris abnormalities (eg, iris atrophy, corectopia, ectropion uveae, peripheral anterior synechiae, iris nevi), decreased vision, and pain. Other features of the syndrome may include fine-hammered silver appearance of the posterior cornea and corneal edema.
Causes
- Glaucoma associated with EVP is due to increased resistance of aqueous outflow from the Schlemm canal and is associated with arteriovenous anomalies, venous obstruction, and idiopathic anomalies.
- Glaucoma associated with ICE syndrome is believed to be due to trabecular meshwork obstruction caused by peripheral anterior synechiae or, less commonly, an abnormal cellular membrane.
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| Treatment & Medication: Glaucoma, Unilateral |
| Follow-up: Glaucoma, Unilateral |
| References |
| Next Page » |
References
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Kirsch M, Henkes H, Liebig T, et al. Endovascular management of dural carotid-cavernous sinus fistulas in 141 patients. Neuroradiology. Jul 2006;48(7):486-90. [Medline].
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Uram M, Zubillaga C. The cutaneous manifestations of Sturge-Weber syndrome. J Clin Neuroophthalmol. Dec 1982;2(4):245-8. [Medline].
Watson PG, Hayreh SS. Scleritis and episcleritis. Br J Ophthalmol. Mar 1976;60(3):163-91. [Medline].
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Further Reading
Keywords
open angle, closed angle, vision loss, visual deficit, open-angle glaucoma, episcleral venous pressure, EVP, glaucoma associated with iridocorneal endothelial syndrome, ICE syndrome
