title: Association of iris crypts with acute primary angle closure.
abstract: To determine the relationship between iris surface features and acute primary angle closure (APAC) in eyes with angle closure.
  
  
  
  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.
  
  
  
  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.
  
  
  
  Occurrence of APAC.
  
  
  
  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.
  
  
  
  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.
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore.
authors.forename: Victor
authors.initials: V
authors.lastname: Koh
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Chua
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Sri Gowtham
authors.initials: SG
authors.lastname: Thakku
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore.
authors.forename: Ryan
authors.initials: R
authors.lastname: Lee
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Monisha E
authors.initials: ME
authors.lastname: Nongpiur
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Mani
authors.initials: M
authors.lastname: Baskaran
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Narayana Nethralaya Eye Hospital, Bangalore, Karnataka, India.
authors.forename: Rajesh S
authors.initials: RS
authors.lastname: Kumar
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Shamira
authors.initials: S
authors.lastname: Perera
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D000208:Acute Disease; D000368:Aged; D044466:Asian People; D016022:Case-Control Studies; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis*; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis
keywords: Diagnostic tests/Investigation; Glaucoma; Iris