title: Comparison of automated and partial coherence keratometry and resulting choice of toric IOL.
abstract: OBJECTIVE
  Consistent astigmatism correction with implantation of a toric intraocular lens (IOL) requires accurate preoperative keratometry. This article compares corneal astigmatism determined by an autokeratometer (Topcon KR-7100) and a partial coherence interferometry keratometer (IOLMaster 500) and considers if any discrepancy ultimately alters in final cylindrical power of the toric IOL for implantation.
  
  
  METHODS
  Keratometry of 235 eyes was performed using both instruments. Corneal astigmatism was transformed into vector components J0 and J45 and cylindrical power at the IOL plane calculated. Comparisons were made using paired t test and correlation and Bland-Altman analyses.
  
  
  RESULTS
  Although interinstrument differences for J0 (p = 0.013), J45 (p = 0.012), and toric IOL cylindrical power (p < 0.001) were statistically significant, a high correlation for these (R = 0.96, 0.90, and 0.90, respectively) was observed. IOLMaster tended to overestimate corneal astigmatism by 0.13 (±0.31) diopters and toric IOL cylinder by 0.11 (±0.18) diopters. Difference in calculated toric IOL cylindrical power correlated poorly with corneal curvature (R = 0.007) and astigmatism (R = -0.004).
  
  
  CONCLUSIONS
  The two keratometers were generally concordant in measuring corneal astigmatism. However, the resultant choice of toric IOL cylinder power differed appreciably in 40% of eyes examined. Therefore, postoperative visual outcome with toric IOL implantation may be optimized by a thorough analysis of biometry data before IOL selection, paying special attention to any difference in corneal astigmatism as measured by more than one instrument.
authors: Moreton Eye Group, 47 Redcliffe Parade, Redcliffe, Queensland 4020, Australia. jeetopt@yahoo.com
authors: Jit B
authors: JB
authors: Ale Magar
authors: Frank
authors: F
authors: Cunningham
authors: Garry
authors: G
authors: Brian
mesh_terms: D001251:Astigmatism / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D001699:Biometry / Q000379:methods*; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D007910:Lenses, Intraocular; D011184:Postoperative Period; D011474:Prosthesis Design; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D012189:Retrospective Studies