Abstract
Background: A new method, the Iida–Shimizu–Shoji (ISS) method, is proposed for calculating intraocular lens (IOL) power that combines the anterior–posterior ratio of the corneal radius of the curvature after laser in situ keratomileusis (LASIK) and to compare the predictability of the method with that of other IOL formulas after LASIK. Methods: The estimated corneal power before LASIK (Kpre) in the double-K method was 43.86 D according to the American Society of Cataract and Refractive Surgery calculator, and the K readings of the IOL master were used as the K values after LASIK (Kpost). The factor for correcting the target refractive value (correcting factor [C-factor]) was calculated from the correlation between the anterior–posterior ratio of the corneal radius of the curvature and the refractive error obtained using this method for 30 eyes of 30 patients. Results: Fifty-nine eyes of 59 patients were included. The mean values of the numerical and absolute prediction errors obtained using the ISS method were −0.02 ± 0.45 diopter (D) and 0.35 ± 0.27 D, respectively. The prediction errors using the ISS method were within ±0.25, ±0.50, and ±1.00 D in 49.2%, 76.3%, and 96.6% of the eyes, respectively. The predictability of the ISS method was comparable to or better than some of the other formulas. Conclusions: The ISS method is useful for calculating the IOL power in eyes treated with cataract surgery after LASIK.
Highlights
The opportunities to perform cataract surgery in patients who have undergone corneal refractive surgeries such as laser in situ keratomileusis (LASIK) are increasing
Where na is the refractive index of intraocular media (1.336), rpost is the radius of curvature of the anterior corneal surface measured by intraocular lens (IOL) master, nc is the refractive index of the cornea (1.333), LOPT is the adjusted axial length considering that is measured with optical biometry (L + 0.65696 − 0.02029 L), LP is the implanted IOL power, and ACDest is the effective lens position (ELP) of the double-K
We examined the predictability of the ISS method, a no-history method
Summary
The opportunities to perform cataract surgery in patients who have undergone corneal refractive surgeries such as laser in situ keratomileusis (LASIK) are increasing. The double-K method, described by Arramberri [7] in 2003, enables more accurate IOL power calculation by estimating the ELP using pre-refractive surgery corneal measurements (Kpre) and the subjective refractive value-derived K values (clinical history method) as Kpost for optical calculations without using the post-refractive surgery corneal measurements. Method, based on the double-K method using the prediction error induced by the ratio of the anterior and posterior radii of the corneal curvature after LASIK This method can calculate IOL frequencies without relying on preoperative data. The accuracy of this new method was compared with other formulas in eyes after LASIK
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