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Editors Selection IGR 22-3

Prognostic Factors: Biometric Parameters and Visual Field Progression in Primary Angle Closure

Victor Koh
Tec Kuan Paul Chew

Comment by Victor Koh & Tec Kuan Paul Chew on:

96490 Ocular Biometric Risk Factors for Progression of Primary Angle Closure Disease: The Zhongshan Angle Closure Prevention Trial, Xu BY; Friedman DS; Foster PJ et al., Ophthalmology, 2021; 0:

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The authors used data from Zhongshan Angle Closure Prevention Trial to detect baseline biometric risk factors for progression of untreated primary angle closure suspect (PACS). There is lack of evidence in the literature that helps to determine if one with PACS, an asymptomatic condition, will benefit from prophylactic procedure or conservative management. This is an important question for a potentially blinding condition such as angle closure disease.

Baseline risk factors to guide management of PACS; The authors identified older age, narrower horizontal AOD500 and flatter horizontal iris curvature (IC) as risk factors for progression. This group of factors can be easily applied as a set of risk assessment to guide management of PACS. The authors highlighted Anterior Segment Optical Coherence Tomography (ASOCT) as a monitoring tool for untreated PACS and it could be used to decide who requires prophylactic procedures in subsequent outpatient reviews.

ASOCT as a risk assessment tool for angle closure; ASOCT is a fast and non-contact investigation that gives reproducible results in a standardized environment. The authors showed that ASOCT parameters such as AOD500 and iris curvature are predictive of angle closure progression. Compared to gonioscopic grading (modified Shaffer classification system), the earlier parameter is a continuous variable which provides a better resolution of angle width characteristics. The latter parameter is a measure of iris bowing which is characteristic of pupil block. Neither slit lamp nor gonioscopy can quantify the extent of iris bowing.

Flatter iris curvature as a risk factor for angle closure progression ; This is interesting as a flatter IC is not characteristic of pupil block but points towards other mechanisms of angle closure such as plateau iris, thick peripheral iris or increased lens vault. Whether prophylactic laser iridotomy will be beneficial in PACS with flat IC is questionable.

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