Astigmatism classification in WTR, ATR or oblique
Updated on version: 1.0.0


Converts the astigmatism to a nominal variable so that the distribution of cases according to the type of astigmatism can be analyzed


Astigmatism classification in WTR, ATR or oblique


This function converts the astigmatism data according to the magnitude and axis to a nominal classification of the variable as a function of the astigmatism orientation. It is possible to introduce the astigmatism in glasses so that a cylinder (-) with a 180º axis represents a WTR astigmatism  or as a function of the maximum power meridian so that an astigmatism (+) at 90º represents a WTR astigmatism.

The function requires a variable with two columns

  • The magnitude of the astigmatism in the first column
  • The axis (magnitude -) or meridian of maximum power (magnitude +)


  1. Alpins NA. A new method of analyzing vectors for changes in astigmatism. J. Cataract Refract. Surg. 1993; 19: 524–33. 2
  2. Thibos LN, Wheeler W, Horner D. Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error. Optom Vis Sci. 1997; 74: 367–75
  3. Abulafia A, Koch DD, Holladay JT, Wang L, Hill W. Pursuing perfection in intraocular lens calculations: IV. Rethinking astigmatism analysis for intraocular lens-based surgery: Suggested terminology, analysis, and standards for outcome reports. J Cataract Refract Surg. 2018;44(10):1169-1174

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