Exploring the optimum step size for defocus curves

James S. Wolffsohn*, Amit N. Jinabhai, Alec Kingsnorth, Amy L. Sheppard, Shehzad A. Naroo, Sunil Shah, Phillip Buckhurst, Lee A. Hall, Graeme Young

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Purpose: To evaluate the effect of reducing the number of visual acuity measurements made in a defocus curve on the quality of data quantified. Setting: Midland Eye, Solihull, United Kingdom. Design: Evaluation of a technique. Methods: Defocus curves were constructed by measuring visual acuity on a distance logMAR letter chart, randomizing the test letters between lens presentations. The lens powers evaluated ranged between +1.50 diopters (D) and -5.00 D in 0.50 D steps, which were also presented in a randomized order. Defocus curves were measured binocularly with the Tecnis diffractive, Rezoom refractive, Lentis rotationally asymmetric segmented (+3.00 D addition [add]), and Finevision trifocal multifocal intraocular lenses (IOLs) implanted bilaterally, and also for the diffractive IOL and refractive or rotationally asymmetric segmented (+3.00 D and +1.50 D adds) multifocal IOLs implanted contralaterally. Relative and absolute range of clear-focus metrics and area metrics were calculated for curves fitted using 0.50 D, 1.00 D, and 1.50 D steps and a near add-specific profile (ie, distance, half the near add, and the full near-add powers). Results: A significant difference in simulated results was found in at least 1 of the relative or absolute range of clear-focus or area metrics for each of the multifocal designs examined when the defocus-curve step size was increased (P<.05). Conclusion: Faster methods of capturing defocus curves from multifocal IOL designs appear to distort the metric results and are therefore not valid. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. © 2013 ASCRS and ESCRS.

Original languageEnglish
Pages (from-to)873-880
Number of pages8
JournalJournal of Cataract and Refractive Surgery
Issue number6
Early online date18 May 2013
Publication statusPublished - Jun 2013

Bibliographical note

Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.


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