title: Relation between optical coherence tomography and optical pachymetry measurements of corneal swelling induced by hypoxia.
abstract: OBJECTIVE
  To determine the relation between optical coherence tomography (OCT) and optical pachymetry (OP) measurements of corneal swelling induced by hypoxia.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  One randomly selected eye of 20 noncontact lens wearers (10 males and 10 females, age 35.6 +/- 9.6 years) was patched during 3 hours of soft contact lens (SCL) wear while the contralateral eye acted as control. Central corneal thickness of both eyes was measured before and after SCL wear using OCT and OP in randomized order.
  
  
  RESULTS
  Baseline central corneal thickness was 523.6 +/- 33.0 microm (mean +/- standard deviation [SD]) measured with OCT and 490.6 +/- 25.5 microm with OP. Immediately after contact lens removal, corneal thickness measured with OCT increased by 13.8 +/- 2.3% compared with 12.1 +/- 1.8% (paired t test: P <.001) measured with OP. Thereafter, corneal thickness decreased at the rate of 5.6% per hour for OCT and 5.4% per hour for OP. The difference in thickness between instruments before lens insertion, which was 33 microm compared with the difference after lens removal (edematous cornea), which ranged from 46 to 41 microm. The difference between instruments decreased during the corneal deswelling period after lens removal. The correlation coefficient between OCT and OP was 0.914 before lens insertion and 0.932 after lens removal.
  
  
  CONCLUSIONS
  This study has demonstrated the difference of corneal thickness measured with OCT and OP. Although both instruments are correlated highly in all conditions tested, OCT may overestimate corneal thickness in normal and edematous corneas.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Ontario, Canada.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wang
authors.forename: Desmond
authors.initials: D
authors.lastname: Fonn
authors.forename: Trefford L
authors.initials: TL
authors.lastname: Simpson
authors.forename: Lyndon
authors.initials: L
authors.lastname: Jones
mesh_terms: D000328:Adult; D003263:Contact Lenses, Hydrophilic; D003315:Cornea / Q000473:pathology*; D015715:Corneal Edema / Q000175:diagnosis* / Q000209:etiology; D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D007368:Interferometry; D008027:Light; D008297:Male; D015203:Reproducibility of Results; D014054:Tomography