title: Differences in corneal astigmatism between partial coherence interferometry biometry and automated keratometry and relation to topographic pattern.
abstract: OBJECTIVE
  To compare the corneal astigmatism values obtained with a partial coherence interferometry (PCI) biometer and an automated keratometer and to evaluate the association between these differences and corneal topographic patterns.
  
  
  METHODS
  Department of Ophthalmology, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
  
  
  METHODS
  Comparative case series.
  
  
  METHODS
  Corneal astigmatism was measured by PCI biometry (IOLMaster) and automated keratometry (RK-F1 autorefractor). Eyes were divided into 3 groups based on the difference in absolute astigmatism values between PCI biometry and automated keratometry (ie, PCI biometry - automated keratometry) as follows: Group 1, more than 0.25 diopter (D); Group 2, within ±0.25 D; Group 3, less than -0.25 D. The topographic maps were grouped into patterns of round, oval, symmetric bow tie, asymmetric bow tie, and irregular. Distributions of topographic patterns according to group and astigmatism values by topographic patterns were evaluated.
  
  
  RESULTS
  The study enrolled 312 eyes. The most common pattern was the asymmetric bow tie (34.6%) followed by symmetric bow tie (20.5%), round (18.9%), irregular (16.3%), and oval (9.6%). The asymmetric bow-tie pattern was the most common in Group 1 and Group 2 (36.1% and 50.0%, respectively); however, in Group 3, the symmetric bow-tie pattern was the most common (32.8%). The distribution of topographic patterns by groups was statistically significantly different (P=.015, Pearson chi-square test).
  
  
  CONCLUSIONS
  The difference in corneal astigmatism between the PCI biometer and automated keratometer may depend on the corneal topography pattern.
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Guro-gu, Seoul, Korea.
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Park
authors.forename: Su Yeon
authors.initials: SY
authors.lastname: Kang
authors.forename: Hyo-Myung
authors.initials: HM
authors.lastname: Kim
authors.forename: Jong-Suk
authors.initials: JS
authors.lastname: Song
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000175:diagnosis*; D001699:Biometry / Q000295:instrumentation; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation; D005260:Female; D006801:Humans; D007368:Interferometry / Q000295:instrumentation; D007429:Intraocular Pressure; D008027:Light; D008297:Male; D008875:Middle Aged; D014065:Tonometry, Ocular