title: Optical coherence tomography-derived corneal thickness asymmetry indices: clinical reference study of normal eyes.
abstract: OBJECTIVE
  To determine 3-dimensional corneal pachymetry distribution characteristics in a large pool of healthy normal patients.
  
  
  METHODS
  Private practice, Athens, Greece.
  
  
  METHODS
  Prospective case series.
  
  
  METHODS
  Spectral-domain anterior segment optical coherence tomography (AS-OCT) was used for measurements of central (CCT) and minimum corneal thickness, thickness asymmetry indices for superonasal-inferotemporal (SN-IT) and superior-inferior (S-I), and focal thinning indices (Min-Med focal thinning, Min-Max thickness range).
  
  
  RESULTS
  The study enrolled 561 eyes. The mean values were CCT, 537.17 μm ± 30.99 (SD) (range 447.0 to 654.0 μm); minimum corneal thickness, 529.01 ± 30.02 μm (range 435.0 to 644.0 μm); SN-IT, 26.32 ± 15.06 μm (range -23.0 to 97.0 μm); S-I, 25.34 ± 15.06 μm (range -36.0 to 93.0 μm); Min-Med, -20.70 ± 5.99 μm (range -7.0 to -50.0 μm); Min-Max, -59.79 ± 16.55 μm (range -156.0 to -23.0 μm). There were significant age-related differences; the mean SN-IT was 22.19 ± 12.40 μm (range -6.0 to 63.0 μm) in the younger group and 30.44 ± 15.07 μm (range -4.0 to 97.0 μm) in the older group (P=.002). The mean S-I was 21.47 ± 12.92 μm (range -5.0 to 70.0 μm) and 29.76 ± 16.27 μm (range -8.0 to 93.0 μm), respectively (P=.001).
  
  
  CONCLUSIONS
  Corneal-thickness asymmetry distribution in a healthy eye population obtained by Fourier-domain AS-OCT showed increased asymmetry in the older group; the asymmetry was not sex dependent. These findings may provide a benchmark for future comparative studies.
  
  
  BACKGROUND
  Dr. Kanellopoulos is a consultant to Alcon Laboratories, Inc., Allergan, Inc., Avedro, Inc., Keramed, Inc., and i-Optics. No other author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From Laservision.gr Clinical and Research Institute (Kanellopoulos, Chiridou, Asimellis), Athens, Greece; New York University Medical School (Kanellopoulos), New York, New York, USA. Electronic address: ajk@brilliantvision.com.
authors.forename: Anastasios John
authors.initials: AJ
authors.lastname: Kanellopoulos
authors.affiliation: From Laservision.gr Clinical and Research Institute (Kanellopoulos, Chiridou, Asimellis), Athens, Greece; New York University Medical School (Kanellopoulos), New York, New York, USA.
authors.forename: Marianthi
authors.initials: M
authors.lastname: Chiridou
authors.affiliation: From Laservision.gr Clinical and Research Institute (Kanellopoulos, Chiridou, Asimellis), Athens, Greece; New York University Medical School (Kanellopoulos), New York, New York, USA.
authors.forename: George
authors.initials: G
authors.lastname: Asimellis
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003315:Cornea / Q000033:anatomy & histology*; D063171:Corneal Pachymetry / Q000379:methods*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011446:Prospective Studies; D012016:Reference Values; D017678:Sex Distribution; D041623:Tomography, Optical Coherence