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C.E. Joslin, E.Y. Tu, T.T. McMahon, J. Sugar; IOL Power Calculation in Eyes Having Undergone Myopic Refractive Surgery and Cataract Surgery . Invest. Ophthalmol. Vis. Sci. 2005;46(13):859.
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© ARVO (1962-2015); The Authors (2016-present)
To compare method accuracy in intraocular (IOL) power calculation for eyes that have undergone myopic refractive surgery and phacoemulsification.
Five consecutive eyes with previous refractive surgery (pre–refractive surgery SE: –4.40 ± 1.90 (SD; D); RK = 4, LASIK = 1) and uncomplicated phacoemulsification were analyzed. IOL power was estimated using our modified contact lens overrefraction (CLO) method and the SRK/T formula. Multiple methods for IOL power calculation were analyzed by comparing IOL prediction error, which is the difference between the implanted and predicted IOL. Methods were analyzed using both the single–K and double–K versions of the SRK/T. Methods analyzed include manual keratometry (K's), clinical history, our CLO method, Hamed’s adjusted post–op K's, Maloney’s modified corneal topography, Wang’s modified Maloney method, and the Feiz–Mannis method. Historical and CLO methods were calculated at the corneal (K) and spectacle (SRx) planes.
The mean SE was –6.77 ± 3.88 pre– and –0.10 ± 0.93 D post–phacoemulsification. Mean logMAR best corrected visual acuity was 0.42 ± 0.20 (20/50–) and 0.08 ± 0.08 (20/25+), respectively. No eyes required additional surgery for refractive complications. The IOL prediction error for each method is presented in the table below. Double–K formulas were less likely to induce hyperopia, but had reduced consistency between cases for every method of IOL power prediction when compared to single–K formulas.
While this series demonstrates unpredictability in IOL power calculation, three important points should be noted: 1) our CLO method can be used to accurately predict IOL power in eyes with dense cataracts and poor visual acuity; 2) our CLO method can successfully be used to estimate corneal power and calculate IOL in post–refractive surgery eyes; and, 3) our CLO method successfully predicted IOL power despite significant refractive error. Further work in a larger series of eyes is warranted to improve our CLO method accuracy and to determine the related confounding and interacting effects of various clinical factors.
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