title: Pretreatment anterior segment imaging during acute primary angle closure: insights into angle closure mechanisms in the acute phase.
abstract: OBJECTIVE
  To describe anterior segment optical coherence tomography (ASOCT) parameters during acute primary angle closure (APAC) before therapeutic interventions and comparative analyses of biometric parameters of APAC eyes with fellow eyes.
  
  
  METHODS
  Prospective, comparative case series.
  
  
  METHODS
  Thirty-one consecutive patients with APAC.
  
  
  METHODS
  All patients underwent ASOCT imaging of both eyes during the attack, before therapeutic interventions were administered. Custom software was used to measure anterior chamber depth (ACD), anterior chamber area (ACA), anterior chamber volume (ACV), iris curvature (I-Curv), iris area (I-Area), lens vault (LV), and angle opening distance (AOD750), trabecular iris space area (TISA750), and iris thickness (IT750) at 750 μm from the scleral spur. Multivariate logistic regression modeling using forward selection was used to determine the most important biometric variables associated with APAC compared with the fellow eye during the attack.
  
  
  METHODS
  Anterior segment biometric parameters associated with APAC.
  
  
  RESULTS
  The mean age of the patients was 60.9±7.5 years, and 11 patients (35.5%) were male. The mean intraocular pressure was 3.8±9.2 mmHg in the APAC eye and 4.2±4.3 mmHg in the fellow eye before treatment (P <0.001). After adjustment for pupil diameter, APAC eyes had smaller ACD, ACA, ACV, I-Curv (all P <0.001), AOD750 (P = 0.037), TISA750 (P = 0.043), I-Area (P = 0.027), and IT750 (P = 0.002) and larger LV (P = 0.041) than fellow eyes. An optimal model consisting of 3 variables (pupil diameter, ACD, and I-Curv) explained 36.7% of the variance in APAC occurrence, with ACD accounting for 18.1% and I-Curv accounting for 14.1% of this variance.
  
  
  CONCLUSIONS
  Shallower ACD and smaller I-Curv were the 2 main anterior segment biometric parameters associated with APAC during the attack. These findings present new insights into the anterior segment biometric parameters of APAC and fellow eyes before therapeutic interventions. Anatomic changes in the anterior segment explained only about one third of the variance in APAC occurrence, and the role of nonanatomic factors require further investigation.
authors.affiliation: Department of Ophthalmology, National University Health System, Singapore; Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.
authors.forename: Chelvin C A
authors.initials: CCA
authors.lastname: Sng
authors.affiliation: Department of Ophthalmology, National University Health System, Singapore.
authors.forename: Maria Cecilia D
authors.initials: MCD
authors.lastname: Aquino
authors.affiliation: Department of Ophthalmology, National University Health System, Singapore.
authors.forename: Jiemin
authors.initials: J
authors.lastname: Liao
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.
authors.forename: Marcus
authors.initials: M
authors.lastname: Ang
authors.affiliation: Department of Ophthalmology, National University Health System, Singapore; Singapore Eye Research Institute and Singapore National Eye Centre, Singapore; Joint Shantou International Eye Center of Shantou University and the Chinese University of Hong Kong, Hong Kong.
authors.forename: Ce
authors.initials: C
authors.lastname: Zheng
authors.affiliation: Department of Ophthalmology, National University Health System, Singapore.
authors.forename: Seng Chee
authors.initials: SC
authors.lastname: Loon
authors.affiliation: Department of Ophthalmology, National University Health System, Singapore; Singapore Eye Research Institute and Singapore National Eye Centre, Singapore. Electronic address: ophchewp@nus.edu.sg.
authors.forename: Paul T K
authors.initials: PTK
authors.lastname: Chew
mesh_terms: D000208:Acute Disease; D000869:Anterior Eye Segment / Q000473:pathology*; D001699:Biometry; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D014065:Tonometry, Ocular