Treating patients with closed-angle glaucoma requires management plan

Accurate diagnosis and appropriate surgical technique, coupled with proper drug treatment, are essential to preventing morbidity.

ByPrin Rojanapongpun, MD

Prin RojanaPongpun

Closed-angle glaucoma is a potentially vision-threatening condition that is further complicated by its subtle and difficult clinical presentation. Closed-angle glaucoma is a more severe form of glaucoma because it causes blindness in more patients than does open-angle glaucoma. Chronic closed-angle glaucoma is usually asymptomatic and often missed because accurate gonioscopy is not routinely performed. Effective disease management is crucial to avoid additional damage and to ensure the long-term viability of the patient’s vision.

Diagnosis and prevalence

Closed-angle glaucoma is the preferred term for the combined progressive disorders of angle closure (mechanical blockage of the drainage angle resulting in elevated IOP) and glaucomatous optic neuropathy (gradual alterations in optic nerve head and nerve fiber structure and function eventually manifesting as visual field defects). As clinic- and population-based surveys have shown,^1,2 most cases of closed-angle glaucoma are asymptomatic chronic closed-angle glaucoma, which develops only gradually after appositional closure or repeated attacks. Closed-angle glaucoma is a common disorder in many Asian countries, most notably in Mongolia where it is diagnosed more frequently than open-angle glaucoma. In a 1998 study conducted in India,¹ primary closed-angle glaucoma reported to be five times more common than primary closed-angle glaucoma, and all cases were chronic in nature. However, prevalence data also indicate that European populations may also have higher rates of closed-angle glaucoma than reported.² A population-based glaucoma survey, the Egna-Neumarkt Glaucoma study in northern Italy, found that almost 25% of all cases of glaucoma were primary closed-angle glaucoma, a rate much higher than previously believed.²

Five-part plan

Because chronic closed-angle glaucoma is associated with a high rate of glaucoma-related blindness, proper management and treatment are essential and usually follow a five-step strategy. Angle closure is an anatomic finding in which the angle is closed or not visible. In the first step, it is documented comprehensively, noting elevations in IOP, previous attacks, and changes in visual function.

Next, the possible mechanisms of angle closure such as pupillary block, plateau iris, thick peripheral iris, lens-related block, and ciliary block are identified, because these mechanisms could increase IOP and eventually lead to the development of glaucomatous optic neuropathy.

Once identified, increased IOP can then be treated, first with medications and then by laser peripheral iridotomy. Laser peripheral iridotomy is an effective treatment for chronic closed-angle glaucoma in its early stages, prior to the formation of large peripheral anterior synechiae, and is also effective if pupillary block is the only suspected underlying mechanism.

In an analysis of Asian patients with closed-angle glaucoma,³ laser peripheral iridotomy effectively prevented a long-term rise in IOP in 88.8% of the fellow eyes after 4 years of follow-up. However, once glaucomatous optic neuropathy is present, only 6% of patients did not require additional treatment after long-term laser peripheral iridotomy (63 months).⁴ These findings suggest that laser peripheral iridotomy is only effective if performing early with angle closure.

Following laser peripheral iridotomy, patients should be reassessed to determine whether addi tional interventions are necessary.

Although outcomes associated with trabeculectomy with or without antifibrotic agents (5-fluorouracil or mitomycin C) vary considerably in patients with chronic closed-angle glaucoma and depend on postoperative care, the procedure remains the preferred subsequent step after laser peripheral iridotomy in treating IOP when other measures have failed.

Iridoplasty can also provide relief to patients with closed-angle glaucoma, although long-term efficacy is unproven in chronic closed-angle glaucoma. Additionally, lens removal, goniosynechialysis, and other treatments should be considered in specific situations.

Best medications

Figure. Combined data over 12 weeks
(P = .0163) at 4 p.m. demonstrates that Travatan significantly enhanced diurnal IOP reduction over the day, compared with Xalatan.

Elevated IOP following iridotomy/iridoplasty is often caused by synechial closure, dysfunctional trabecular meshwork, or other uncorrected mechanisms of angle closure. In these and many other cases in which IOP is inadequately controlled, medication is indicated.

Currently, prostaglandins are considered the best agent for reducing IOP in chronic closed-angle glaucoma. There does not appear to be a correlation between the amount of angle opening and efficacy, with some data indicating that prostaglandins may be useful in almost totally closed angles.⁵

Results from the EXACT study⁶ indicate that once-daily Xalatan (latanoprost 0.005%; Pfizer) reduces IOP significantly more than twice-daily timolol. In the 12-week study, patients receiving Xalatan had 8.2 mm Hg mean reductions from baseline at week 12, compared with 5.2 mm Hg for patients receiving timolol. Additionally, more patients treated with Xalatan were able to reach prespecified treatment goals (P < .001 for IOP of 18 mm Hg or less).

In a recent multinational study,⁷ the IOP-lowering effect of Xalatan was measured against that of Travatan (travoprost 0.004%; Alcon) in chronic closed-angle glaucoma. At the 4 p.m. time point, Travatan significantly reduced diurnal IOP from baseline (P = .0162) compared with Xalatan. Both study drugs significantly reduced mean IOP at 9 a.m. (Figure). Additionally, 59.8% of patients in the Xalatan arm and 64.6% of patients in the Travatan arm achieved mean IOP responses of 18 mm Hg or less at 4 p.m. Both of these once-daily agents were reported to be safe and well tolerated.

Evidence-based management

Following treatment with these and other proven regimens, it is necessary to monitor IOP as well as optic nerve head and visual field. Periodic gonioscopy should be performed, and treatment is to be adjusted accordingly if needed.

References

Jacob A, Thomas R, Koshi SP, Braganza A, Muliyil J. Prevalence of primary glaucoma in an urban south Indian population.Indian J Ophthalmol. 1998;46:81-86.

Bonomi L, Marchini G, Marraffa M, Bernardi P, De Franco I, Perfetti S, Varotto A. Epidemiology of angle-closure glaucoma: prevalence, clinical types, and association with peripheral anterior chamber depth in the Egna-Neumarkt Glaucoma Study. Ophthalmology. 2000;107:998-1003.

Ang LP, Aung T, Chew PT. Acute primary angle closure in an Asian population: long-term outcome of the fellow eye after prophylactic laser peripheral iridotomy. Ophthalmology. 2000;107:2092-2096.

Alsagoff Z, Aung T, Ang LP, Chew PT. Long-term clinical course of primary angle-closure glaucoma in an Asian population. Ophthalmology. 2000;107:2300-2304.

Kook MS, Cho HS, Yang SJ, Kim S, Chung J. Efficacy of latanoprost in patients with chronic angle-closure glaucoma and no visible ciliary-body face: a preliminary study. J Ocul Pharmacol Ther. 2005;21:75-84.b

Chew P, Aung T, Aquino M, RojanaPongpun P. Intraocular pressure-reducing effects and safety of latanoprost versus timolol in patients with chronic angle-closure glaucoma. Ophthalmology. 2004;111:427-434.

Chew PTK, RojanaPongpun P, Euswas A, et al for the Travatan CACG Study Group. Travatan CACG Study Group. Intraocular pressure lowering effect and safety of travoprost 0.004% and latanoprost 0.005% for the treatment of chronic angle closure glaucoma. Asian J Ophthalmol. 2006;8:2-8.

Prin RojanaPongpun, MD, is the chief of the Glaucoma Service, Department of Ophthalmology, Chulalongkorn University and Hospital, King Chulalongkorn Memorial Hospital, Bangkok, Thailand.