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Guang-ming George Dai, Dimitri Alex Chernyak, Sanjeev Kasthurirangan; Reducing Spherical Aberration in LASIK Surgeries Using Periphery Modification Function. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5751. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate treatment algorithms for reducing post-operative induction of spherical aberration for LASIK surgeries.
A previous study for reducing post-operative spherical aberration (SA) used an optimized linear filter (OLF) model to represent the biomechanical and healing effect during the surgery. Unfortunately, a subsequent clinical study showed suboptimal outcomes. Since the optimization already matched between the model and the clinical outcomes in an optimal way, it leaves little room for improvement without a change of the model. In this new study, we construct a periphery modification function (PMF) where the strength of the function can be linearly changed, thus becoming a scalable model. This PMF is multiplied to the treatment targets point-by-point, thus also eliminates issues seen in the previous approach, such as noise amplification issues. Based on prior clinical study data where no effort to reduce SA was intended, and the clinical study where a deconvolution technique was employed to reduce SA, an extrapolation can be employed to tune the strength of the PMF such that a desirable level of post-operative SA can be designed
For myopia, current treatment induces about 0.03 μm (over a 6 mm diameter) of spherical aberration per diopter. With the deconvolution approach, this was reduced to a little below 0.02 μm, but not to zero as desired. Although the deconvolution approach used a very different technique (OLF), its effect in terms of reducing spherical aberration can be related to PML where the same amount of SA reduction is achieved. The deconvolution approach, if represented with the PML instead, has a strength of about 0.062. In order to reduce the per-diopter SA to zero, the strength of PML is estimated to be 0.125, roughly doubling the strength used in the deconvolution approach. With this new approach, it requires doubling the extra ablation depth (17% as compared to 8.6% in the deconvolution) when compared to normal wavefront-guided LASIK for myopia. The advantage of this approach is its scalability, allowing for multiple trial-and-error studies to achieve desirable outcomes. Furthermore, it is possible to design personalized treatments with desirable amount of post-operative SA, after this approach is proven to work.
Use of periphery modification function allows scalable control of post-operative spherical aberration in LASIK surgeries.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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