Estimation of effective lens position using a method independent of preoperative keratometry readings

Ian Dooley, Sofia Charalampidou, John Nolan, James Loughman, Laura Molloy, Stephen Beatty

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Purpose: To evaluate the validity of a keratometry (K)-independent method of estimating effective lens position (ELP) before phacoemulsification cataract surgery. Setting: Institute of Eye Surgery, Whitfield Clinic, Waterford, Ireland. Design: Evaluation of diagnostic test or technology. Methods: The anterior chamber diameter and corneal height in eyes scheduled for cataract surgery were measured with a rotating Scheimpflug camera. Corneal height and anterior chamber diameter were used to estimate the ELP in a K-independent method (using the SRK/T [ELPrs] and Holladay 1 [ELPrh] formulas). Results: The mean ELP was calculated using the traditional (mean ELPs 5.59 mm ± 0.52 mm [SD]; mean ELPh 5.63 ± 0.42 mm) and K-independent (mean ELPrs 5.55 ± 0.42 mm; mean ELPrh ± SD 5.60 ± 0.36 mm) methods. Agreement between ELPs and ELPrs and between ELPh and ELPrh were represented by Bland-Altman plots, with mean differences (± 1.96 SD) of 0.06 ± 0.65 mm (range -0.59 to +0.71 mm; P=.08) in association with ELPrs and -0.04 ± 0.39 mm (range -0.43 to +0.35 mm; P=.08) in association with ELPrh. The mean absolute error for ELPs versus ELPrs estimation and for ELPh versus ELPrh estimation was 0.242 ± 0.222 mm (range 0.001 to 1.272 mm) and 0.152 ± 0.137 mm (range 0.001 to 0.814 mm), respectively. Conclusion: This study confirms that the K-independent ELP estimation method is comparable to traditional K-dependent methods and may be useful in post-refractive surgery patients.

Original languageEnglish
Pages (from-to)506-512
Number of pages7
JournalJournal of Cataract and Refractive Surgery
Issue number3
Publication statusPublished - Mar 2011


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