Futoshi Taketani, MD,PhD, Characteristics of the spherical aberrations of three aspherical intraocular lenses by measurement in a model eye Department of Ophthalmology, Nara Medical University Futoshi Taketani, MD,PhD, Yoshiaki Hara , MD,PhD No author has a financial interest in any material or method mentioned.

Introduction The spherical aberration (SA) at 6mm diameter for the Acrysof IQ SN60WF (Alcon Laboratories, Inc.) is indicated to be -0.20 µm, while for the Tecnis ZA90003 (Advanced Medical Optics Inc.), the figure is -0.27 µm. However, manufacturers do not disclose tolerance and standard deviation values for these SA. Purpose To evaluate the SA of aspherical intraocular lenses (IOLs) using a model eye.

Material and Methods Model eye cornea : Anterior radius curvature 7.67 mm Posterior radius curvature 7.20 mm Spherical aberration +0.22 µm for 6mm aperture diameter Central thickness 1.00 mm Aspherical IOLs were placed in a fluid-filled model eye designed to closely duplicate the optical condition of an IOL when implanted in the human eye. The schema of the model eye is shown in Figure 1. The IOLs were fixed to an IOL holder, which had an outer diameter of 12 mm, an inner diameter of 10 mm, a thickness of 1 mm and an artificial pupil diameter of 7.5 mm. The IOL holder, complete with IOL, was set inside the model eye. A cross-sectional image of the model eye configured for measurement with the Hartmann-Schack aberrometer. An artificial retina back plate moved back and forth for both spherical and astigmatism errors were less than ± 0.25 D, to measure 10.0 D to 30.0 D IOLs The Acryfold PC60AD (HOYA Corp.) , the Acrysof IQ SN60WF, and the Tecnis ZA9003 are selected for comparison in this study. (Table 1) Characteristics of the three types of IOLs

The SA of each IOL was calculated according to the following formula: Material and Methods 2 First, we measured 9 pieces for 20 D IOLs from each of the three manufacturers (n = 9). Second, we tested IOLs between the ranges of 10–17 D and 26–30 D, in 1 D increments (n = 13); and IOLs of powers 18–25 D in 0.5 D increments (n = 15) (total n = 28). We measured 37 IOLs in total for each manufacturer. IOL position was measured using EAS-1000 (NIDEK, Japan) by Scheimpflüg image analysis. If the IOL position decentered ± 0.10 mm and/or tilted ≥2 degrees, the IOL was remounted on the model eye and the measurements for HOA and IOL position were repeated. High-order aberrations of the model eye were measured with the commercially available Hartman-shack aberrometer (KR9000 PW; Topcon, Tokyo, Japan). (Figure 2) Analysis of aberrations in this study was conducted by measuring the 6 mm wavefront aperture diameters in the model eye. Calculation of the root mean square (RMS) error, matching to 3rd–6th order Zernike coefficients, was done with the KR-9000 PW program. Model eye KR9000PW Figure 2 The SA of each IOL was calculated according to the following formula: IOL SA = SA of the measured model eye – SA of the model eye cornea (= 0.22 µm)

Material and Methods 3 For the three IOL types, a one-sample t-test was performed on 20 D IOLs, to compare the IOL SA indicated by each manufacturer with the actual value measured in our study. One-factor ANOVA was used to evaluate the differences of HOAs, HOAs root mean square (RMS), IOL tilt and decentration for the three types of the aspheric IOL. Pearson’s correlation analysis (r value) was used to evaluate the relationship between the spherical aberrations of each IOL, and IOL power, for 6 mm aperture diameters. A P value ≤0.05 was considered to be statistically significant.

Results There was no significant difference in IOL tilt (P = 0.06) and IOL decentration (P = 0.326) among these three manufactures. 0.326 0.028±0.028 0.045±0.031 0.042±0.027 Decentration （ｍｍ） 0.06 1.43±0.26 1.14±0.36 1.22±0.67 Tilt（°） P value* ZA9003 SN60WF PC60AD The IOL tilt and decentration of the three types of IOLs The measured +20D IOL SA for the AC60AD (P = 0.002) was significantly smaller than the value indicated by the manufacturer (-0.18 µm). However, no significant differences in the IOL SA were found between the measured and the indicated values for the SN60WF and the ZA9003. There was no significant difference in 3rd , 4th and 3rd – 6th order aberration RMS among three groups. <0.001 -0.274±0.039 -0.201±0.007 -0.199±0.013 IOL　SA 0.675 0.176±0.064 0.156±0.071 0.182±0.049 3rd – 6th RMS -0.054±0.039 0.020±0.007 0.021±0.013 SA (Model eye) 0.069 0.058±0.036 0.032±0.006 0.042±0.011 4th RMS 0.797 0.152±0.077 0.149±0.075 0.169±0.054 3rd RMS P value* ZA9003 SN60WF PC60AD RMS: Root Mean Square 3rd RMS: 3rd order aberration RMS 4th RMS: 4th order aberration RMS 3rd -6th RMS: 3rd to 6th order aberration RMS SA: Spherical aberration

Results 2 A B C A: PC60AD (p < 0.0001, r = -0.684) Y=-0.00407x – 0.12181 A B Y=-0.00233x – 0.2317 C The correlation between the IOL power and the spherical aberration; A: PC60AD (p < 0.0001, r = -0.684) B: SN60WF (p = 0.929) C: ZA9003 IOL (p = 0.011, r = -0.470) The negative correlations for were found between IOL powers and the SA for the Acryfold PC-60AD and the Tecnis ZA9003.

Conclusion This model eye was effective to evaluate the HOAs of IOLs. Negative correlations were found between IOL powers and the SA for AC60AD and ZA9003. The implantation of aspherical IOL may result in a negative SA, which exceeds the value indicated by the manufacturer, especially for higher power IOLs. Acknowledgment We would like to thank Jiro Hidaka for helping to construct the model eye. Our these findings was accepted in Journal of cataract & refractive surgery, and in press.