Estimating total corneal astigmatism from anterior corneal data

Kristian Næser, Giacomo Savini, Jesper Flethøj Bregnhøj

Research output: Contribution to journalArticlepeer-review


Purpose: To determine keratometric astigmatism (KA), posterior corneal astigmatism (PCA), and total corneal astigmatism (TCA) in 951 normal eyes, to establish a model for estimating TCA from anterior corneal data, and to test this method in a new group of eyes with toric intraocular lenses (TIOLs). Methods: We used a Pentacam HR (high-resolution) Scheimpflug camera to determine KA, PCA, and TCA in 951 normal eyes. A model to estimate TCA from anterior corneal data was evaluated by the difference (=error) between the measured TCA and the estimated value. The model was tested in 40 eyes with TIOLs. Results: KA, TCA, and PCA averaged 1.06 (±0.85) D, 1.05 (±0.83) D, and 0.33 (±0.17) D. The error of the model to estimate TCA averaged zero with an SD of ±0.21 D. Application of this model and of direct Pentacam TCA measurements in TIOL calculation gave similar results, namely a slight reduction of overcorrection in with-the-rule astigmatism, but an eradication of undercorrection in against-the-rule astigmatism. Conclusions: It was possible to estimate TCA accurately from anterior corneal data with a new formula. However, application of both this model on keratometric data and of direct Pentacam measurements in a group of 40 eyes with TIOLs did not completely eradicate the refractive error in TIOL calculation. More studies comparing Pentacam TCA and refractive astigmatism are required.

Original languageEnglish
Pages (from-to)828-833
Number of pages6
Issue number7
Publication statusPublished - Jul 1 2017


  • Meridional power
  • Polar value analysis
  • Posterior corneal astigmatism
  • Torsional power
  • Total corneal astigmatism

ASJC Scopus subject areas

  • Ophthalmology


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