2020–2021 BCSC Basic and Clinical Science Course™

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2020–2021 BCSC Basic and Clinical Science Course™

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10 Glaucoma

Chapter 9: Primary Angle Closure

The Primary Angle-Closure Spectrum

Primary Angle-Closure Suspect

The term primary angle-closure suspect (PACS) is defined by the presence of a narrow angle with ≥180° of appositional iridotrabecular contact, without overt signs of PAC (IOP elevation or PAS) or glaucomatous optic nerve damage. PACS eyes are at risk for developing angle-closure disease (acute angle-closure crisis, PAC, or PACG).

Only a small percentage of PACS eyes develop angle-closure disease, and the predictive value of gonioscopy is relatively poor even when performed by experienced clinicians. When performing gonioscopy, the clinician should observe the effect that the examination light has on the angle recess. For example, pupillary constriction stimulated by the slit-lamp beam itself may open the angle, and the narrow recess may go unrecognized (Video 9-1; Fig 2-9).

VIDEO 9-1 Angle apposition when going from light to dark conditions.

Courtesy of Shan Lin, MD.

Scan the QR code or access the video at www.aao.org/bcscvideo_section10.

Provocative tests such as pharmacologic pupillary dilation and the dark-room prone-position test can precipitate a limited form of angle closure and thus have been used in an attempt to predict which patients might develop angle closure and benefit from an iridotomy. However, the recent Zhongshan Angle-Closure Prevention (ZAP) study showed that provocative testing (15-minute dark-room prone position) is not predictive of an angle-closure attack or development of glaucoma (although eyes were excluded from the study if there was a 15 mm Hg elevation in IOP on either mydriatic dilation or dark-room, prone provocative testing). Anterior segment imaging is under investigation in hopes it may be a better predictor of angle-closure disease (see the section Anterior Segment Imaging in Chapter 4).

He M, Jiang Y, Huang S, et al. Laser peripheral iridotomy for the prevention of angle closure: a single-centre, randomized controlled trial. Lancet. 2019;393(10181):1609–1618.

Figure 9-2 Anterior segment optical coherence tomography of a narrow angle. A, Angle closure is evident when the angle is imaged with lights off. B, The same angle is much more open when it is imaged with lights on. C, Narrow angles due to plateau iris (before laser iridotomy). D, Same meridian with persistent narrow angles after laser iridotomy.

(Parts A and B courtesy of Yaniv Barkana, MD; parts C and D courtesy of David A. Lee, MD.)

Figure 9-3 Plateau iris syndrome. A, Eye with plateau iris has a flat iris plane but shallow angle recess (arrow). Note that the midperipheral angle appears deeper (double arrow) than the narrow angles associated with pupillary block. B, Plateau iris syndrome after laser peripheral iridoplasty, with a much deeper angle recess (arrow).C, Image shows the classic “double-hump” sign. D, Ultrasound biomicroscopy shows peripheral iris contact with Schwalbe line, anterior to the angle recess, in a case of plateau iris configuration

(Parts A and B courtesy of M. Roy Wilson, MD; part C courtesy of Wallace L.M. Alward, MD; part D courtesy of Robert Ritch, MD.)

Management

It is considered reasonable to perform a laser peripheral iridotomy (LPI; Fig 3-9) in an eye that meets the criteria for PACS (Videos 9-2, 9-3). However, iridotomy is not necessary for all PACS patients, and the decision of whether to treat an asymptomatic individual with narrow angles is based on an accurate assessment of the anterior chamber angle, the clinical judgment of the ophthalmologist, and the patient’s preference. (See the sidebar Treatment Controversies for further discussion.) Any patient with narrow angles should be advised of the symptoms of acute angle closure, the need for immediate ophthalmologic attention if symptoms occur, and the value of long-term periodic follow-up.

VIDEO 9-2 Angle apposition before LPI.

Courtesy of Shan Lin, MD.

Courtesy of Shan Lin, MD.

VIDEO 9-3 Angle apposition after LPI, with angle opening.

Courtesy of Shan Lin, MD.

TREATMENT CONTROVERSIES

Laser Peripheral Iridotomy

Whether to perform an LPI in patients who meet the criteria for PACS remains controversial. The Zhongshan Angle-Closure Prevention (ZAP) trial randomized 1 eye of subjects with PACS to LPI, with the contralateral eye serving as a control. The study showed that very few cases in either group progressed to PACG or an acute attack. There was a significantly lower risk of conversion to PAC with treatment; however, most cases of conversion were attributed to PAS formation alone, without ocular hypertension. Overall, the results suggest that performing LPIs for PACS on a population basis is not recommended. However, on an individual basis, the clinician needs to consider whether an LPI is appropriate based on narrowness of the angle, the presence of symptoms such as eye discomfort in the evening, and other factors relevant to the particular patient, including his or her personal preference given the available evidence.

An LPI should be considered for patients who have a narrow angle with PAS, increased segmental trabecular meshwork pigmentation, a history of previous acute angle closure, or other risk factors for angle closure (ACD <2.0 mm, strong family history). The status of the lens and the potential benefit of cataract surgery should also be taken into consideration.

Furthermore, there is controversy as to whether an LPI should be performed in eyes in which most or all of the angle is closed with PAS. Such eyes have limited outflow facility and may have marked IOP increase as a result of the dispersed pigment and debris. In some cases, the IOP elevation is refractory to medications and requires filtering surgery. Thus, caution should be exercised in such cases, and avoidance of the LPI may be the better course of action.

Iridoplasty

Another controversial area is whether to perform iridoplasty in angle closure. There is evidence that iridoplasty is effective in further widening a narrow angle after iridotomy (Video 9-4). However, there is no strong evidence that iridoplasty is beneficial in preventing development of future glaucoma or progression of existing glaucoma.

VIDEO 9-4 Iridoplasty in the peripheral iris.

Courtesy of Robert Ritch, MD.

Lensectomy

Clear lens extraction (LE) may be beneficial to certain patients with angle closure. The EAGLE study was a prospective randomized trial that evaluated the safety and efficacy of LE in subjects with no or non–visually significant cataracts, compared with standard treatment with LPI and medications. Subjects enrolled were ≥50 years, without visually significant cataracts, and with newly diagnosed PAC with IOP ≥30 mm Hg or PACG. The study found that LE resulted in lower IOP, less medication usage, better quality of life, and similar visual field progression as the control group.

Azuara-Blanco A, Burr J, Ramsay C, et al; EAGLE study group. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): a randomised controlled trial. Lancet. 2016;388(10052):1389–1397.

He M, Jiang Y, Huang S, et al. Laser peripheral iridotomy for the prevention of angle closure: a single-centre, randomised controlled trial. Lancet. 2019;393(10181):1609–1618.

Lim DK, Chan HW, Zheng C, et al. Quantitative assessment of changes in anterior segment morphology after argon laser peripheral iridoplasty: findings from the EARL study group. Clin Exp Ophthalmol. 2019;47(1):33–40.

Ng WS, Ang GS, Azuara-Blanco A. Laser peripheral iridoplasty for angle-closure. Cochrane Database Syst Rev. 2012;(2):CD006746.

Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.

10 Glaucoma

Chapter 9: Primary Angle Closure

The Primary Angle-Closure Spectrum

Primary Angle-Closure Suspect

Management

TREATMENT CONTROVERSIES

OUR SITES

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