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M. T. Aaron, J. Porter, T. J. Brunstetter, D. J. Tanzer, R. A. Applegate; Preoperative Factors Predict Postoperative Changes in Visual Acuity for Myopic Laser Refractive Surgery Patients. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6161.
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© ARVO (1962-2015); The Authors (2016-present)
In order to better assess which individuals will experience a postoperative gain or loss in visual acuity (VA) prior to surgery, we developed a model, based on preoperative measures, to predict changes in photopic high contrast (HC) VA after Wavefront-Guided (WFG) Laser Assisted in situ Keratomileusis (LASIK).
Photopic HC logMAR acuity (luminance = 108 cd/m2), spherical equivalent (SE) refractive error, natural pupil diameter and Shack-Hartmann wavefront error (WFE) measurements were collected on right eyes of 15 myopic subjects (mean SE = -6.05 ± 1.37D) preoperatively and 3 months post-WFG LASIK. Best subset and stepwise regression analyses were performed using the preoperative measures and 31 single-value image quality metrics (based on preoperative WFEs) to determine a model to predict the change in HC acuity after WFG LASIK. The model was tested on an independent, 14-eye data set in which similar pre- and postoperative measures were collected. A Bland-Altman analysis was used to compare the predicted change in HC acuity to the measured change in HC acuity from pre-to postoperative states.
The best subset regression model predicted 67.7% of the variance in the change in photopic HC acuity (p =0.006). The variables in the model (in order of entry) were preoperative HC acuity (accounted for 45.6% of the variance), and two preoperative image quality metrics, half width at half height (HWHH) and pupil fraction (PFWc). According to the Bland-Altman analysis, the model predicted 76% of the change in HC logMAR acuity in the independent test population to within ± 1 line and all of the independent test population to within ± 2 lines.
Our model predicts changes in HC acuity for the majority of tested patients based on a combination of preoperative factors that can easily be measured prior to refractive surgery. By testing more patients and incorporating non-optical pre-op factors (e.g., biomechanical properties), the model could be further refined to better predict which patients will experience gains or losses in HC acuity prior to WFG LASIK.
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