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Arch Ophthalmol. 2004;122:1230-1232.

Elevated intraocular pressure (IOP) associated with blood in the Schlemm canal may be associated with many different conditions.^1-3 To our knowledge, we describe a previously unreported case of a patient with recurrent, intermittent spikes in IOP associated with episodic and transient blood in the Schlemm canal. Whenever the patient was examined because of elevated IOP in one or both eyes, gonioscopy disclosed the presence of blood in varying quadrants of the Schlemm canal in the affected eye(s). Whenever IOP was normalized, with or without medical therapy, the blood was no longer visualized.

Report of a Case
A 38-year-old woman of Latin American descent sought medical care because of right ocular pain, redness, and decreased visual acuity of approximately 12 hours' duration. The pain was not relieved by ibuprofen. The patient reported a history of similar ocular episodes that had occurred intermittently during the preceding 2 years. Her medical history was significant for systemic hypertension and left elbow surgery; her blood pressure was 160/90 mm Hg at the time of examination. Therewas no significant ocular, family, or social history.

On initial examination, visual acuities were 20/40 OD and 20/25 OS, with a mid-dilated, minimally reactive pupil in the left eye. We found no proptosis, orbital bruits, or pulsating exophthalmos. The right conjunctival region had a mild red appearance, and mild corneal edema or haze was noted in the right eye. There was no apparent dilation of the episcleral veins. The left anterior segment appeared normal. Goldmann applanation tonometry measurements were 55 mm Hg OD and 17 mm Hg OS. In the right eye, gonioscopy showed open angles with blood in the Schlemm canal inferiorly, temporally, and superiorly (Figure 1). Gonioscopic findings of the left angle structures were unremarkable. Dilated funduscopic examination of the right eye showed mild vascular tortuosity without leakage on fluorescein angiography. Ophthalmodynomometry measurements were 70 mm Hg OD and 60 mm Hg OS (both within normal limits). The elevated IOP was initially treated with an intensive course of topical medications and oral agents (eg, acetazolamide and glycerin). Once the IOP was normalized, the patient was prescribed an antiglaucoma regimen of timolol maleate, latanoprost, and dorzolamide hydrochloride.

View larger version (75K): [in this window] [in a new window] Gonioscopic view of the angles of the right eye. Blood can be seen in the Schlemm canal.

During the next 5 months, the patient experienced recurrent, intermittent episodes of increased IOP in either or both eyes. These IOP spikes were always associated with the gonioscopic presence of blood in varying quadrants of the Schlemm canal. Whenever IOP was normalized in the affected eye(s), with or without medical therapy, the blood was no longer visualized. The patient also experienced 2 mild episodes of white-colored cells and flare noted in the anterior chamber, both resolving within a few days. At any of the visits, no signs of hyphema, either on slitlamp or gonioscopic examination, were noted.

A computed tomographic scan of the head (with contrast) showed that both superior ophthalmic veins were normal; no mass effect was noted. An open magnetic resonance imaging scan (with gadolinium enhancement) was also read as within normal limits; the cavernous sinus and ophthalmic veins were unremarkable. Automated visual fields (created with the 24-2 SITA program; Humphrey Instruments, Inc, Dublin, Calif) were normal in both eyes. Measurement of the episcleral venous pressure was within normal limits in both eyes. Doppler imaging of the jugular, subclavian, and upper extremity venous system showed normal values for compression and velocity. Extensive laboratory evaluation results (including a full hypercoagulable workup), as well as fluorescent treponemal antibody absorption test results, erythrocyte sedimentation rate, and beta human chorionic gonadotropin, rapid plasma reagin, antinuclear antibody, serum angiotensin-converting enzyme, and Lyme antibody titers, were all within normal limits. The chest x-ray film was also within normal limits. Of note, the patient was found to have a positive sickle cell trait on hemoglobin electrophoresis (HbAS trait; such individuals have 1 copy of the normal hemoglobin A gene and 1 copy of the hemoglobin S gene).

Comment
In our patient, the differential diagnosis included increased episcleral venous pressure due to Sturge-Weber syndrome, dural cavernous sinus fistula, carotid-cavernous sinus fistula, superior vena cava syndrome, orbital arteriovenous fistula, jugular vein obstruction, thyroid ophthalmopathy, and idiopathic familial entities.³ Other causes of blood in the Schlemm canal include artifact due to the compression of episcleral veins with the Goldmann or Allen-Thorpe goniolens, ocular hypotony (following injury, inflammation, or cyclodialysis), and pathologic deep arterial anastomosis from a deep limbal artery to the Schlemm canal.^1-2 During our extensive diagnostic evaluation (including normal values on episcleral venous pressure testing), these diagnoses were eventually excluded.

A systematic review of the literature demonstrated one previous case report⁴ of a patient with HbAS trait who was first seen because of a single episode of elevated IOP in one eye associated with blood in the Schlemm canal. However, our patient had multiple intermittent episodes of elevated IOP associated with transient episodes of blood in the Schlemm canal, which appeared in either eye. Another recent case report⁵ described a patient with a 3-year history of uveitis-glaucoma-hyphema syndrome who was diagnosed as having HbAS trait on the basis of cytopathologic examination findings of the submitted aqueous fluid during posterior-chamber intraocular-lens explantation and anterior-chamber washout.

While patients with sickle cell disease (either hemoglobin SS [HbSS] [individuals having 2 copies of the hemoglobin S gene] or HbSC [individuals having 1 copy of the hemoglobin S gene and 1 copy of the hemoglobin C gene]) are well known to have systemic and ocular vaso-occlusive episodes, little is known about the extent of increased coagulation activity in individuals with HbAS trait.⁶ Although HbAS trait disorders are usually asymptomatic in nature, we theorize that in our patient, the HbAS trait caused localized sickling of the red blood cells (with subsequent sludging) in the Schlemm canal. In support of this theory, a recent study⁶ reports that individuals with HbAS trait have increased coagulation activity (although it is lower than in patients with HbSC or HbSS disease). Moreover, Goldberg⁷ has reported that patients with sickle cell hemoglobinopathies (including AS) have a higher percentage of sickled erythrocytes in their anterior chambers than in their circulating venous blood. Injection of sickle cell erythrocytes (AS, SS, SC, and Sthal [consisting of 1 copy of the hemoglobin S gene and 1 copy of the hemoglobin -thalassemia gene]) into the anterior chambers of living human, monkey, or guinea pig eyes results in sickling of the red blood cells with resultant IOP elevation.⁸ Furthermore, a vicious cycle of hypoxia and acidosis are known to contribute to increased sickling of the erythrocytes.⁹ In our patient, we suggest that intermittent episodes of sickled red blood cells in the trabecular meshwork (as a result of the HbAS trait) contributed to her transient elevations in IOP.

The authors have no relevant financial interest in this article.

This study was supported in part by the Homer McK. Rees Scholar Award, New York, NY (Dr Tsai); the Eye Surgery Fund (Dr Tsai), New York; and unrestricted departmental grants from Research to Prevent Blindness, Inc, New York.

This study was presented in part at the Annual Meeting of the Association for Research in Vision and Ophthalmology; May 8, 2002; Fort Lauderdale, Fla.

AUTHOR INFORMATION

Robyn E. Horowitz, MD; Max Forbes, MD; Steven M. Podos, MD; James C. Tsai, MD

Correspondence: Dr Tsai, Harkness Eye Institute, Columbia University College of Physicians and Surgeons, 635 W 165th St, New York, NY 10032 (jct2002{at}columbia.edu).

REFERENCES
1. Phelps CD, Asseff CF, Weisman RL, Podos SM, Becker B. Blood reflux into Schlemm's canal. Arch Ophthalmol. 1972;88:625-631. FREE FULL TEXT 2. Phelps CD. Arterial anastomosis with Schlemm's canal: a rare cause of secondary open-angle glaucoma. Trans Am Ophthalmol Soc. 1985;83:304-315. PUBMED 3. Greenfield DS. Glaucoma associated with elevated episcleral venous pressure. J Glaucoma. 2000;9:190-194. WEB OF SCIENCE | PUBMED 4. Friedman AH, Halpern BL, Friedberg DN, Wang FM, Podos SM. Transient open-angle glaucoma associated with sickle cell trait: report of 4 cases. Br J Ophthalmol. 1979;63:832-836. FREE FULL TEXT 5. Sharma A, Ibarra MS, Piltz-Seymour JR, Syed NA. An unusual case of uveitis-glaucoma-hyphema syndrome. Am J Ophthalmol. 2003;135:561-563. PUBMED 6. Westerman MP, Green D, Gilman-Sachs A, et al. Coagulation changes in individuals with sickle cell trait. Am J Hematol. 2002;69:89-94. FULL TEXT | WEB OF SCIENCE | PUBMED 7. Goldberg MF. Sickled erythrocytes, hyphema, and secondary glaucoma, I: the diagnosis and treatment of sickled erythrocytes in human hyphemas. Ophthalmic Surg. 1979;10:17-31. WEB OF SCIENCE | PUBMED 8. Goldberg MF, Dizon R, Raichand M. Sickled erythrocytes, hyphema, and secondary glaucoma, II: injected sickle cell erythrocytes into human, monkey, and guinea pig anterior chambers: the induction of sickling and secondary glaucoma. Ophthalmic Surg. 1979;10:32-51. WEB OF SCIENCE | PUBMED 9. Goldberg MF, Dizon R, Moses VK. Sickled erythrocytes, hyphema, and secondary glaucoma, VI: the relationship between intracameral blood cells and aqueous humor pH, PO2, and PCO2. Ophthalmic Surg. 1979;10:78-88. WEB OF SCIENCE | PUBMED

SECTION EDITOR: W. RICHARD GREEN, MD

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