Aims To assess dynamic change of iris area (Iarea) and volume (VOL) with physiologic pupil dilation for progression of primary angle closure suspects.
Methods Participants underwent baseline examinations including gonioscopy and anterior segment OCT (AS-OCT) as part of the Zhongshan Angle Closure Prevention Trial. The AS-OCT images were obtained both in the dark and light. Progression was defined as development of primary angle closure or an acute angle closure attack. Static ocular biometrics and dynamic changes were compared between progressors and non-progressors and multivariable logistic regression was developed to assess risk factors for progression.
Results A mean 16.8% decrease in Iarea and a mean 6.26% decrease in VOL occurred with pupil dilation, while 22.96% non-progressors and 40% progressors presented VOL increases with pupil dilation. Iarea in light and dark and VOL in light were significantly smaller in progressors. In a multivariable logistic model, older age (p=0.008), narrower horizontal angle opening distance (AOD) 250 µm from the scleral spur (AOD250, p=0.001), flatter iris curvature (IC, p=0.006) and lower loss of iris volume (ΔVOL, p=0.04) were significantly associated with progression. With receiver operating characteristic analysis, the area under the curve for ΔVOL alone was 0.621, while that for the combined index (age, AOD250, IC and ΔVOL) was 0.824. Eyes with elevated intraocular pressure had less VOL loss compared with progressors developing peripheral anterior synechiae alone (p=0.055 for ΔVOL adjusted for pupil enlargement).
Conclusion A smaller change in ΔVOL is an additive risk factor to identify eyes more likely to develop angle closure disease.
Trial registration number ISRCTN45213099.
Data availability statement
Data are available upon reasonable request.
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Contributors Research design was conducted by PJF, DF and MH. Data acquisition and research execution were carried out by YJ, SH and WH. Study idea was developed by HQ. Data analysis and interpretation was performed by CL. The manuscript was finished by HQ and CL, proofread and revised by PJF, DF and MH. CL is the guarantor.
Funding This work is supported by the Fight for Sight (grant 1655; UK), the Sun Yat-sen University 5010 Project Fund (grant 2007033; China), the National Natural Science Foundation of China (grant 81420108008; China), Fundamental Research Funds of the State Key Laboratory in Ophthalmology (China) and Moorfields Eye Charity (previously Special Trustees of Moorfields Eye Hospital, no award/grant number). The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. CL, YJ, SH, WH, HQ, MH, PJF and DF had access to all the data in the study. MH, PJF, HQ and DF had final responsibility for the decision to submit for publication.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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