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A. Fabrikant, G. Dai; Error Budget Analysis for Refractive Surgery. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4191.
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© ARVO (1962-2015); The Authors (2016-present)
Classification and theoretical analysis of error sources for refractive surgery, numerical simulations of ablation errors, comparative study and prioritization of error sources.
A GUI-based software was developed for simulation of system errors. Given the laser parameter tolerances it allows a comparative factor analysis of ablation errors and Monte-Carlo statistical simulations of total errors induced by any selected subset of system deviations. The error analysis was performed for several treatment types, including myopia, hyperopia, myopic astigmatism, hyperopic astigmatism, and mixed astigmatism.
The comparative factor analysis shows that systematic errors, which stem from imperfect system calibration and stay the same from pulse to pulse during ablation, are typically more important than random errors. We found that the highest contributors to the total RMS error were ablation calibration, eye registration, inaccuracy of the laser spot positioning, and eye tracking latency. Spherical aberrations are mostly affected by errors in ablation depth, eye registration, eye tracking latency and sampling rate.Spherical aberrations, caused by ablation inaccuracy due to all error sources, stays typically below the level of 0.2 um (defined as abs(mean)+std) in optical path difference (OPD), but for some cases it may reach up to 0.4 um (the upper boundary defined as abs(mean)+2*std), which can make a difference to post-operative aberrations.
Prioritization of error sources, based on given system tolerances, is needed for further improvement of laser refractive surgery. System calibration accuracy, eye registration, and quality of eye tracking are the most important factors of the total system quality.
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