title: Anterior chamber angle measurements using Schwalbe's line with high-resolution fourier-domain optical coherence tomography.
abstract: OBJECTIVE
  To use Fourier-domain optical coherence tomography (OCT) to measure the angle opening distance at Schwalbe's line (AOD-SL) and determine its value in anterior chamber angle assessment.
  
  
  METHODS
  Horizontal scans of the nasal and temporal anterior chamber angles in glaucoma subjects were performed at 830 nm wavelength Fourier-domain OCT. Images were graded by 2 ophthalmologists who assessed the visibility of Schwalbe's line (SL), anterior limbus (AL), scleral spur (SS), and angle recess (AR). AOD-SL was measured with computer calipers. SL was manually identified by the termination of the corneal endothelium. Gonioscopy was used to classify anterior chamber angles according to a modified Shaffer system. Spearman ρ analysis was performed to assess correlation between AOD-SL and modified Shaffer grade. A cutoff value of AOD-SL for diagnosing occludable angles (modified Shaffer grade ≤ 1) was determined by receiver operating characteristic (ROC) analyses.
  
  
  RESULTS
  Thirty-five glaucoma subjects (65 eyes) were enrolled. SL, AL, AR, and SS were visible by OCT in 97.7%, 99.2%, 87.3%, and 80.8% of eyes, respectively. Nasal and temporal AOD-SLs were 322.6 ± 200.2 µm and 341.4 ± 197.4 µm, respectively. Correlation coefficients between AOD-SL and modified Shaffer grade were 0.80 (nasal) and 0.81 (temporal). The diagnostic cutoff value of AOD-SL for occludable angles was 290 µm. The areas under the ROC curve, sensitivity, specificity values were 0.90, 0.80, 0.87 (nasal) and 0.90, 0.85, 0.77 (temporal), respectively.
  
  
  CONCLUSIONS
  The measurement of AOD-SL by Fourier-domain OCT is highly correlated with gonioscopy and may be a useful noncontact method for assessing angle closure risk.
authors: *Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China †Doheny Eye Institute and Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA.
authors: Bing
authors: B
authors: Qin
authors: Brian A
authors: BA
authors: Francis
authors: Yan
authors: Y
authors: Li
authors: Maolong
authors: M
authors: Tang
authors: Xinbo
authors: X
authors: Zhang
authors: Chunhui
authors: C
authors: Jiang
authors: Catherine
authors: C
authors: Cleary
authors: David
authors: D
authors: Huang
mesh_terms: D000368:Aged; D000867:Anterior Chamber / Q000473:pathology*; D003315:Cornea / Q000033:anatomy & histology*; D005260:Female; D005583:Fourier Analysis; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D011446:Prospective Studies; D012372:ROC Curve; D041623:Tomography, Optical Coherence; D014065:Tonometry, Ocular; D014129:Trabecular Meshwork / Q000473:pathology*; D014792:Visual Acuity / Q000502:physiology