Prospective Comparison of Manifest Refraction with Autorefraction Before and After Sub-Bowman Keratomileusis Joel D. Hunter MD Frank Schwendeman OD Daniel S. Durrie MD Durrie Vision Overland Park, KS

Potential Conflicts of Interest Drs. Hunter and Schwendeman have no financial relationships to disclose Presently Dr. Durrie is a clinical investigator for: Alcon Allergan AMO Bausch and Lomb IntraLase Refractec Acufocus WaveTec Avedro Encore Vision LenSx Wavefront Science NeuroVision High Performance Optics OcuSense QuestVision Visiometrics Tracey Technologies Topcon Ocular Optics

Purpose To evaluate accuracy of autorefraction compared with manifest refraction To investigate whether the traditional phoropter is still the “gold standard” for accurate pre- or post-operative evaluation in a refractive surgery practice

Study Design 3-month prospective clinical trial includes 300 eyes at pre-operative, 1-month and 3-month post-operative visits for Sub-Bowman Keratomileusis Myopia or hyperopia with or without astigmatism were treated with SBK using the IntraLase for flap creation and the Allegretto Wavelight for ablation. Two consecutive measurements at each visit: Nidek ARK-530A Topcon KR-8800 Nidek OPD-Scan II

Results - Accuracy These results are concerned with how far away the patient's average autorefraction is from the "true" value (manifest) Because refractions are a combination of sphere and cylinder, comparison can only be done by vector analysis Vector manipulations were used to determine the error

Autorefractor vs. MRx Histograms

Autorefractor vs. MRx Double-Angle Plots

Results - Repeatability These results are concerned with the difference between the values of the 1st and 2nd measurement on the same device The “distance” between the measurements was based on the magnitude of the vector difference between measurements (i.e. vector analysis)

Results - Repeatability Manifest Refraction – most disparity Spherical Equivalent: 0.17 D Cylinder: 0.23 D Nidek ARK-530A – least disparity Spherical Equivalent: 0.07 D Cylinder 0.11 D Topcon KR-8800 Spherical equivalent: 0.12 D Cylinder: 0.12 D OPD-Scan II Spherical equivalent: 0.14 D Cylinder: 0.15 D

Interpretation Modern autorefraction is within 0.27 D of spherical equivalent and 0.32 D of cylinder or less, depending on the device used, when compared to manifest refraction. Modern autorefraction is highly repeatable, with spherical equivalent and cylinder changes averaging <0.25 D for all three machines tested.