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Toric Intraocular Lens Calculations—Reply

Michael Goggin, FRCSI(Ophth), MS; Sacha Moore, FRCOphth; Adrian Esterman, PhD
Arch Ophthalmol. 2012;130(7):947-949. doi:10.1001/archophthalmol.2012.700.
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We thank Dr Simpson for pointing out the typographical error in our article.1 He is correct. The formula should have read E = F /[1 + (d /1.336) F]. All calculations in the article were done using this correct formula, and the formula in the article has been corrected. With regard to the suitability of this formula for the task of predicting toric IOL outcome, we have demonstrated that it predicted the outcome better than the Alcon online calculator. He is right that it is related to the formula for adjusting effective powers between contact lenses and spectacle lenses, but the incorporation of an index of refraction for aqueous and cornea (1.336) makes it suitable for calculation of equivalent powers within the eye. The US patent application document for the online Alcon toric calculator2 uses such formulas in a more detailed manner, calculating vergence at the cornea and the first and second principal planes of the IOL.


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July 1, 2012
Giacomo Savini, MD; Kenneth J. Hoffer, MD
Arch Ophthalmol. 2012;130(7):947-949. doi:10.1001/archophthalmol.2011.2747.
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