title: Refractive predictability of partial coherence interferometry and factors that can affect it.
abstract: OBJECTIVE
  To evaluate the refractive predictability of a partial coherence interferometry (PCI) biometry device (IOL Master) for cataract surgery and to investigate factors that may affect it.
  
  
  METHODS
  Retrospective review of 209 eyes from 151 patients that had undergone preoperative PCI biometry and an uneventful phacoemulsification cataract surgery with posterior chamber intraocular lens (IOL) implantation was conducted. Prediction error defined as the intended refraction minus the postoperative refraction in spherical equivalent (SE) and the absolute error were analyzed according to IOL calculation formulas, patient characteristics, preoperative visual acuity (VA) and refraction, posterior subcapsular cataract (PSC), signal-to-noise ratio (SNR), and axial length (AL).
  
  
  RESULTS
  The overall refractive predictability of the PCI device was good. Generally, the SRK/T formula performed better than the SRK-II formula. Refractive predictability was slightly worse in eyes with >or=+2.0 diopters (D) of preoperative SE (with both SRK-II and SRK/T) and in eyes with an AL<or=23.0 mm (only with SRK-II. No other factors significantly affected the refractive predictability of the PCI, although poor VA, dense PSC, and poor SNR were closely interrelated.
  
  
  CONCLUSIONS
  The SRK/T formula performed significantly better than the SRK-II formula. Eyes with an AL<or=23.0 mm were associated with significantly greater hyperopic shifts in postoperative refraction with the SRK-II formula, but not with the SRK/T formula. A preoperative SE>or=+2.0D was related to a significantly greater hyperopic shift in postoperative refraction. With proper verification of measured data and a suitable IOL calculation formula, good refractive predictability is expected from PCI biometry regardless of patient characteristics, preoperative VA, SNR, PSC, and AL.
authors.affiliation: Department of Ophthalmology, Seoul Veterans Hospital, Seoul, Korea.
authors.forename: Seung Mo
authors.initials: SM
authors.lastname: Kim
authors.forename: Joohyun
authors.initials: J
authors.lastname: Choi
authors.forename: Sangkyung
authors.initials: S
authors.lastname: Choi