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G. M. Gavanski, M. J. McCarthy; Evaluation of Intraocular Lens Power Calculation Methods After Myopic Laser Refractive Surgery. Invest. Ophthalmol. Vis. Sci. 2008;49(13):398. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the accuracy of corneal power estimation methods in conjunction with popular formulas for determining intraocular lens (IOL) power after myopic laser refractive surgery.
This was a retrospective chart review of post-refractive IOL implants at our practice between the years 2004-07. A total of 18 patients operated on for cataracts which had prior PRK (Photorefractive Keratectomy) or LASIK (Laser-Assisted in Situ Keratomileusis) for myopia were included in the study. True IOL power was back-calculated using the stable postoperative manifest refraction and implanted IOL power. The Holladay (I and II), SRK/T, Hoffer Q and Haigis formulas were evaluated in conjunction with the R-Factor, Shammas.cd, Latkany, Aramberri Double-K and the "gold standard" Clinical History Method (CHM) amongst a number of other corneal power adjustment techniques. The relatively new, no-history Haigis-L and Shammas.PL formulas were also included in the analysis.
The top performing formulas in terms of overall accuracy and minimizing hyperopic "refractive surprises" were the Shammas.PL, Latkany SRK/T and the Haigis-L which resulted in 78% (15/18), 67% (12/18) and 50% (9/18) of the eyes within ±0.5D spherical equivalent, respectively. The popular Haigis, Holladay II and SRK/T with the CHM performed poorer with 45% (8/18), 33% (6/18) and 33% (6/18) of the eyes within ±0.5D spherical equivalent, respectively.
IOL calculation after laser refractive surgery remains a challenge. Attesting to this is the abundance of corneal power estimation techniques and IOL formulas available. Based on our preliminary data, the Shammas.PL, Latkany SRK/T and Haigis-L are more accurate and result in less hyperopic "refractive surprises" than the popular Holladay II, Haigis or SRK/T used with the Clinical History Method. The Shammas.PL and Haigis-L have the added benefit of not requiring laser refractive surgical history which is often unavailable or of questionable accuracy.
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