Compute the addition or the cylinder from IOL to spectacle plane


Computes the effective addition or the Cylinder from the Intraocular Lens (IOL) plane to the spectacle plane by the Holladay's equation


Compute the addition or the cylinder from IOL to spectacle plane


The addition of a Multifocal Intraocular Lens or the cylinder of a toric IOL usually are given by the manufacturer at the IOL plane. However, the effective addition and the cylinder of the lens can vary among patients depending on some variables such as corneal power, effective lens position and IOL power. The main purpose of this function is to compute the effective addition or the cylinder of a IOL considering these variables by means of the Holladay's equation.


  1. Holladay JT. Refractive power calculations for intraocular lenses in the phakic eye. Am J Ophthalmol. 1993;116:63-6.
  2. Savini G, Hoffer KJ, Lombardo M, et al (2016) Influence of the effective lens position, as predicted by axial length and keratometry, on the near add power of multifocal intraocular lenses. J Cataract Refract Surg 42:44–49.
  3. Eom Y, Song JS, Kim HM (2016) Spectacle plane add power of multifocal intraocular lenses according to effective lens position. Can J Ophthalmol / J Can d’Ophtalmologie 1–7.
  4. McKee HD, Jhanji V (2016) Theoretical Effect of Lens Position and Corneal Curvature on the Near Focal Point of Multifocal Intraocular Lenses. J Refract Surg 32:64–66.

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