title: Changes in anterior segment morphology in response to illumination and after laser iridotomy in Asian eyes: an anterior segment OCT study.
abstract: OBJECTIVE
  Using the anterior segment optical coherence tomography (AS-OCT) to quantify changes in anterior segment morphology going from light to dark and following laser iridotomy (LI).
  
  
  METHODS
  Prospective observational study. 17 consecutive subjects without peripheral anterior synechiae undergoing LI were evaluated using gonioscopy and AS-OCT. Angle configuration including angle opening distance (AOD) at 500 microns anterior to the scleral spur, AOD(500), trabecular-iris space area up to 750 microns from the scleral spur, TISA(750) and the increase in angle opening going from dark to light conditions was determined.
  
  
  RESULTS
  Both mean AOD(500) and TISA(750) increased nearly threefold going from dark to light. Both also significantly increased following LI (p<0.001) as did gonioscopic grading of the angle in all quadrants (p<0.001, McNemar's test). Angles were more than twice as wide on average in the dark after LI than before LI (p<0.05). Both the mean absolute change and the mean proportionate change in AOD(500) and TISA(750) when going from light to dark were greater after LI than before (p<0.05).
  
  
  CONCLUSIONS
  Increased illumination as well as LI resulted in significant widening of the anterior chamber angle. AS-OCT (which does not require a water bath and can be performed with the patient at the slit lamp) identified similar magnitude changes as those previously reported using ultrasound biomicroscopy (UBM). Furthermore, the angle appears to open more both in absolute terms and and proportionate terms in response to illumination after LI.
authors.affiliation: National University Hospital, Singapore.
authors.forename: Jovina L S
authors.initials: JL
authors.lastname: See
authors.forename: Paul T K
authors.initials: PT
authors.lastname: Chew
authors.forename: Scott D
authors.initials: SD
authors.lastname: Smith
authors.forename: Winifred P
authors.initials: WP
authors.lastname: Nolan
authors.forename: Yiong-Huak
authors.initials: YH
authors.lastname: Chan
authors.forename: David
authors.initials: D
authors.lastname: Huang
authors.forename: Ce
authors.initials: C
authors.lastname: Zheng
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Foster
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
mesh_terms: D000368:Aged; D000869:Anterior Eye Segment / Q000473:pathology*; D044466:Asian People; D001699:Biometry / Q000379:methods; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000208:ethnology / Q000473:pathology / Q000601:surgery*; D006068:Gonioscopy; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D032801:Iridectomy; D053685:Laser Therapy; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D011446:Prospective Studies; D041623:Tomography, Optical Coherence