Abstract
Purpose: :
To investigate potential wavefront–derived metrics to provide a better means of assessing visual quality after refractive surgery.
Methods: :
Human data was obtained from 431 eyes enrolled in LASIK clinical trials. This population included both myopic and hyperopic eyes treated either with conventional or wavefront–guided surgery. Exam data including wavefront measurements and low contrast cycloplegic uncorrected visual acuity (lccUCVA) measures were obtained 6–months after refractive surgery. Analysis was performed using numerous image and pupil plane metrics over varying pupil diameters. Metrics were also tested for correlations with symptoms such as glare, halo, night driving and blurry vision.
Results: :
Tested metrics included both novel and previously published parameters (e.g., Strehl ratio, PSF peak, MTF volume, etc.). Looking at the optimal wavefront diameter, best correlation between lccUCVA and most of the metrics was observed for pupil diameters between 4.5 and 5.0 mm. A metric defined using suitable combination of metrics yielded correlations higher than the correlation obtained with the best individual metric and also gave stable correlation over a larger range of pupil diameters. Using the best metrics, the highest correlation obtained applying the entire data set was 0.80. Using regression analysis, based on 95% confidence interval, outliers were removed. This results in removing ∼10% of the patient data improving the correlation to 0.84. Some metrics correlate well with symptoms such as glare, blurry vision but the subjective nature of the measurements themselves prevents us from drawing any final conclusions.
Conclusions: :
Using a large data set over a wide range of refractive error, we obtained correlations of 0.80 with a combination metric and a correlation coefficient of 0.84 with outliers removed (10% of the patient data). With this metric, we not only obtained high correlations over an optimal pupil size, but maintained the strong correlation over a range of pupil radii. With refinement these parameters should yield useful information regarding vision quality and calculation of the effective clinical refraction. An objective method is required for measuring symptoms such as glare to confirm the metric correlations.
Keywords: refractive surgery: optical quality • visual acuity • refractive surgery: LASIK