Article Text

Download PDFPDF
Association of iris crypts with acute primary angle closure
  1. Victor Koh1,2,
  2. Jacqueline Chua1,3,
  3. Yuan Shi1,
  4. Sri Gowtham Thakku1,
  5. Ryan Lee1,2,
  6. Monisha E Nongpiur1,3,
  7. Mani Baskaran1,3,
  8. Rajesh S Kumar1,4,
  9. Shamira Perera1,3,
  10. Tin Aung1,2,3,
  11. Ching-Yu Cheng1,2,3
  1. 1Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore
  2. 2Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore
  3. 3Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore
  4. 4Narayana Nethralaya Eye Hospital, Bangalore, Karnataka, India
  1. Correspondence to Dr Ching-Yu Cheng, Singapore Eye Research Institute, 20 College Road, The Academia, Level 6, Discovery Tower, Singapore 169856, Singapore; chingyu.cheng{at}


Purpose To determine the relationship between iris surface features and acute primary angle closure (APAC) in eyes with angle closure.

Design Case-control study involving Asian patients diagnosed with previous APAC, primary angle closure suspect (PACS), primary angle closure (PAC) and primary angle closure glaucoma (PACG) at an eye centre in Singapore between August 2012 and January 2015.

Methods Participants underwent ophthalmic examination and digital slit-lamp iris photography. Iris surface features were graded based on crypts, furrows and colour. Fellow eyes of APAC were compared with PACS and PAC/PACG eyes with regard to their iris surface features.

Main outcome measure Occurrence of APAC.

Results A total of 309 patients (71 APAC, 139 PACS, 47 PAC and 52 PACG) were included (mean age: 67.7±7.2 years and 36.6% male). Compared with PACS, higher crypt grade was significantly associated with lower odds of APAC (OR=0.58 for one grade higher in crypt grade; p=0.027, adjusted for age, gender, ethnicity and pupil diameter). The results remained similar when compared with PAC/PACG group (OR=0.58 for one grade higher in crypt grade; p=0.043). We did not observe any significant associations between iris furrows or colour with presence of APAC.

Conclusions Our study comprising Asian eyes with angle closure suggests that the presence of a higher crypt grading may be protective for APAC. As such, assessing iris surface architecture for crypts could be a new measure for risk stratification of developing APAC in eyes with angle closure.

  • Glaucoma
  • Diagnostic tests/Investigation
  • Iris

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Contributors VK, JC and C-YC had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: C-YC and TA. Acquisition, analysis or interpretation of data: all authors. Drafting of the manuscript: VK, JC and C-YC. Critical revision of the manuscript for important intellectual content: all authors. Statistical analysis: YS and JC. Obtained funding: C-YC. Administrative, technical or material support: all authors. Study supervision: C-YC. VK, JC, YS, SGT, MEN, MB, RSK, SP, TA and C-YC prepared and reviewed the main manuscript, tables and figures.

  • Funding The study is funded by National Medical Research Council (NIG/1069/2012 and CIRG/1442/2016), Singapore. C-YC is supported by National Medical Research Council (CSA/033/2012).

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval SingHealth Centralised Institutional Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.