Estimation accuracy of surgically induced astigmatism on the cornea when neglecting the posterior corneal surface measurement

Li Sheng Cheng, Ching Yao Tsai, Jui-Fang Tsai, Shiow Wen Liou, Jau Der Ho

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Purpose: To evaluate the accuracy of corneal surgically induced astigmatism (SIA) estimation when neglecting the posterior corneal surface measurement. Methods: Fifty right eyes undergoing phacoemulsification were measured with a rotating Scheimpflug camera (Pentacam; Oculus Inc., Wetzlar, Germany) both before and after surgery. Clear corneal incisions with one suture were used in the phacoemulsification surgery. The keratometric corneal SIA (KSIA) was derived using the anterior corneal surface measurement and the keratometric index (1.3375) while neglecting the posterior corneal surface measurement. The Pentacam-derived total corneal SIA (PSIA) was derived by vergence tracing and polar value analysis [KP(135) and KP(180)] of the measurements on both corneal surfaces. Results: The mean arithmetic estimation errors of the KSIA for the PSIA were 0.16 ± 0.32 (-0.52 to 1.14) D for the KP(135), and -0.02 ± 0.30 (-0.75 to 1.29) D for the KP(180). There was a significant difference between the KP(135) components of the KSIA and PSIA. Bivariate analysis revealed a statistically significant difference between the combined means of the KSIA and PSIA. Overall, 24% had either a KP(135) component of the KSIA that differed by > 0.50 D from that of the PSIA or a KP(180) component of the KSIA that differed by > 0.50 D from that of the PSIA. The blurring strength caused by neglecting the posterior corneal measurement was > 0.50 D in 24% of eyes. Conclusion: Neglecting the posterior corneal surface measurement may lead to significant deviation in the corneal SIA estimation after phacoemulsification in a proportion of eyes.

Original languageEnglish
Pages (from-to)417-422
Number of pages6
JournalActa Ophthalmologica
Volume89
Issue number5
DOIs
Publication statusPublished - Aug 2011

Keywords

  • cataract
  • phacoemulsification
  • posterior cornea
  • surgically induced astigmatism

ASJC Scopus subject areas

  • Ophthalmology

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