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).
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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.
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.
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.