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Degree of angle closure and extent of peripheral anterior synechiae: an anterior segment OCT study
  1. D H W Su1,
  2. D S Friedman2,
  3. J L S See3,
  4. P T K Chew3,4,
  5. Y-H Chan4,
  6. W P Nolan2,3,
  7. S D Smith5,
  8. D Huang6,
  9. C Zheng3,
  10. Y Li5,6,
  11. P J Foster7,
  12. T Aung1,4
  1. 1
    Singapore National Eye Centre, Singapore
  2. 2
    Wilmer Eye Institute and Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
  3. 3
    National University Hospital, Singapore
  4. 4
    Yong Loo Lin School of Medicine, National University of Singapore, Singapore
  5. 5
    Cole Eye Institute, Cleveland, OH, USA
  6. 6
    Doheny Eye Institute, University of Southern California Keck School of Medicine, Los Angeles, CA, USA
  7. 7
    Moorfields Eye Hospital and Institute of Ophthalmology, London, UK
  1. T Aung, Glaucoma Department, Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore 168751; tin11{at}


Aims: To evaluate the relationship between angle width as determined by anterior segment optical coherence tomography (AS-OCT) and the presence of peripheral anterior synechiae (PAS).

Methods: This was a prospective observational case series in which 203 subjects with primary angle closure or open angles were recruited. Images of the nasal, temporal and inferior angles were obtained with AS-OCT in dark conditions. Subjects then underwent gonioscopy by an independent examiner who was masked to the AS-OCT findings. PAS were identified by gonioscopy and defined as abnormal adhesions of the iris to the angle that were at least half a clock hour in width and present to the level of the anterior trabecular meshwork or higher. The total clock hours of PAS were recorded.

Results: Sixty-eight subjects (33.5%) were PACS, 76 subjects (37.4%) had PAC/PACG, 14 (6.9%) had primary open angle glaucoma, and 45 (22.2%) subjects were normal with open angles. There was a weak but significant correlation between the angle opening distance (AOD), trabecular iris space area (TISA) and angle recess area (ARA) with clock hours of PAS (Spearman’s correlation coefficients = −0.30, −0.32 and −0.32, respectively, p<0.001). The mean values of the AOD, TISA and ARA in the nasal, temporal and inferior quadrants were significantly less in eyes with PAS compared with those without (p<0.001, Mann–Whitney U test). Analysis by quadrant showed that these parameters were smaller in the nasal and temporal quadrants in eyes with PAS (p<0.01).

Conclusions: Angle width determined by AS-OCT and the extent of PAS were weakly correlated, and angle width was significantly smaller in eyes with PAS.

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  • Funding: National University of Singapore: Grant numbers R-191000007101 and R-191000007112.

  • Competing interests: Carl Zeiss Meditec loaned the anterior segment OCT for the study and provided technical support. Dr Aung has received research funding and financial support for travel to conferences from Carl Zeiss Meditec. Dr Smith has received financial support for travel to conferences from Carl Zeiss Meditec. Dr Friedman has previously been a consultant to Carl Zeiss Meditec. Dr Huang receives patent royalty and research grant from Carl Zeiss Meditec.