Corneal Spherical Aberration in a Population of Patients Measured by 3 Different Instruments Mohamed A Guenena, MD Helga P Sandoval, MD, MSCR Kerry D Solomon, MD Magill Research Center for Vision Correction, Storm Eye Institute Medical University of South Carolina, Charleston The authors does not have any financial interests in the products mentioned

Background Spherical aberration (SA) is a fourth-order higher-order aberration in which peripheral light rays are refracted more than the central ones Can be positive or negative depending on where the light rays focuses Leads to image spread on the retina instead of point focus Average cornea SA is +.27µ compensated by the lens negative SA in healthy individuals. After cataract surgery, if a spherical IOL is implanted, it will add more positive SA to the eye

Background Several aspheric monofocal IOLs have been developed with different SA values to compensate for the corneal SA Tecnis Z9000 -.27µ AcrySof SN60WF -.20µ nanoFLEX Collamer -.019µ Sofport AO 0 Tecnis SN60WF Sofport AO nanoFLEX

Background Literature suggests getting the patient closest to 0 SA to achieve the optimum quality of vision Correct selection of the aspheric IOLs will depend mainly on SA measurements of the cornea

Purpose To compare the measurements of corneal spherical aberration obtained by the Atlas Corneal Topography (Carl Zeiss, Jena, Germany), Galilei Dual Scheimpflug Analyzer (Ziemer, Port, Switzerland) and the OPD-Scan II (Nidek, Tokyo, Japan). Atlas Corneal Topography Galilei Dual Scheimpflug Analyzer OPD-Scan II

Methods A pilot study SA were measured in patients undergoing cataract surgery before dilation. SA measured in the 6 mm optical zone No history of ocular surgery or injury No ocular pathology other than cataract All measurements were done by single trained observer Difference between measurements were analyzed

Methods Reports from the 3 tested instruments

Measurements 8 eyes of 6 patients All females Average age: 73 years ( 63-81) Atlas Galilei OPD Eye 1 0.226 0.37 0.267 Eye 2 0.274 0.25 0.129 Eye 3 0.094 0.18 0.206 Eye 4 0.3 0.217 Eye 5 0.341 0.29 0.255 Eye 6 0.266 0.28 Eye 7 0.285 0.27 0.261 Eye 8 0.161 0.31 0.169 Average 0.220 (± 0.05) 0.281 0.228 (± 0.08)

Difference between Galilei and OPD measurements compared to Atlas Galilei - Atlas OPD-Atlas Eye 1 0.041 0.144 Eye 2 -0.145 -0.024 Eye 3 0.112 0.086 Eye 4 0.037 0.12 Eye 5 -0.086 -0.051 Eye 6 -0.011 0.014 Eye 7 -0.015 Eye 8 0.008 0.149 Average -0.009 (± 0.079) 0.053 (± 0.081) Positive sign = overestimate Negative sign = underestimate

Conclusion This pilot study showed high consistency of measurements of SA among the 3 tested instruments This finding can help the surgeons choose the proper aspheric IOL regardless of which measuring instrument is used. More studies are needed to determine the optimal SA surgeons need to target

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