title: Anterior chamber width measurement by high-speed optical coherence tomography.
abstract: OBJECTIVE
  To measure anterior chamber (AC) width and other dimensions relevant to the sizing of phakic intraocular lenses (IOLs) with a high-speed optical coherence tomography (OCT) system.
  
  
  METHODS
  Cross-sectional observational study.
  
  
  METHODS
  Both eyes of 20 normal volunteers.
  
  
  METHODS
  A novel high-speed (4000 axial scans/second) OCT prototype was developed for anterior segment scanning. The system uses long wavelength (1310 nm) for deeper angle penetration, rectangular scanning for undistorted imaging, and short image acquisition time (0.125 seconds) to reduce motion error. Three horizontal cross-sectional OCT images (15.5 mm wide and 6 mm deep) of the anterior segment were obtained from each eye with real-time image display to guide centration on the corneal apex. Image processing software was developed to correct for image warping resulting from index transitions. Anterior chamber dimensions were measured using computer calipers by 3 expert raters (ophthalmologists). Analysis of variance was used to determine interrater, interimage, right versus left eye, and intersubject standard deviation (SD) of OCT measurements.
  
  
  METHODS
  Anterior chamber width (recess to recess), AC depth, and crystalline lens vault as measured by OCT; external white-to-white (WTW) corneal diameter (CD) as measured by Holladay-Godwin gauge.
  
  
  RESULTS
  The mean AC width was 12.53+/-0.47 mm (intereye SD), and the mean corneal diameter was 11.78+/-0.57 mm. Optical coherence tomography measurement of AC width has good repeatability from image to image (SD, 0.134 mm), but there was significant difference between raters (SD, 0.215 mm). Estimation of AC width from WTW CD by linear regression was relatively inaccurate (residual SD, 0.41 mm). The mean AC depth was 2.99+/-0.323 mm (intereye SD), with repeatability of less than 0.001 mm (interimage SD), and the mean crystalline lens vault was 0.39+/-0.27 mm with 0.023 mm repeatability.
  
  
  CONCLUSIONS
  Reproducible OCT AC biometry was demonstrated using a high-speed OCT prototype. Further improvement in reproducibility may be achieved by automating the measurements with a computer. Direct OCT AC width measurement may improve sizing of angle-supported AC IOLs over conventional estimation by WTW CD. The measurement of AC depth and lens vault also may be useful for other types of phakic AC IOLs.
authors.affiliation: Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Goldsmith
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Maria Regina
authors.initials: MR
authors.lastname: Chalita
authors.forename: Volker
authors.initials: V
authors.lastname: Westphal
authors.forename: Chetan A
authors.initials: CA
authors.lastname: Patil
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Rollins
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Izatt
authors.forename: David
authors.initials: D
authors.lastname: Huang
mesh_terms: D000328:Adult; D000867:Anterior Chamber / Q000033:anatomy & histology*; D001699:Biometry; D001837:Body Weights and Measures; D003315:Cornea / Q000033:anatomy & histology; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000033:anatomy & histology; D007910:Lenses, Intraocular; D008297:Male; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*