A System for the Design, Manufacture and Test of Custom Lenses With Known Amounts of High Order Aberrations

Abstract

Abstract: : Purpose: To design a system for manufacture and test of custom lenses with known amounts of high order aberrations. This process is a direct precursor to wavefront-guided ablations that can be done on human corneas. Method: Analytically defined wavefront surfaces can be represented as a linear combination of Zernike polynomials on a unit circle corresponding to the pupil plane of the eye. Such a surface can be used to create a treatment plan, - a pattern of laser pulses designed to ablate the surface on a given material. The treatment table for a specific surface has been input to the VISX STAR^TM laser to perform the ablation on a flat plastic plate. The lens created in the process was measured in VISX WaveScan^TM instrument (Hartmann-Shack wavefront sensor) in order to measure the lens optical properties and express them in turn as a linear combination of Zernike polynomials. The resulting wavefront was compared to the initial analytically defined wavefront for two different surfaces. Results: In addition to the good qualitative agreement, the theoretical and the measured surfaces also agree quantitatively. The noise found in the higher Zernike terms is an artifact of the entire process, and its amplitude should be indicative of the overall noise levels of the system once the alignment issues are resolved. For both tested surfaces the amplitude of measured Zernike coefficients for terms higher then the ones present in the input wavefront is at least an order of magnitude smaller then the amplitude of the signal. Conclusion: We have shown that the ablation process on calibration plastic closely matches the expected wavefront surface both qualitatively and quantitatively. This demonstrates the accuracy of each step of the process from lens manufacturing to lens validation. We have also addressed the issues that have a significant impact on lens properties, such as translational and rotational alignments of the treatment area and the measurement area of the lens.

Keywords: 454 laser • 500 optical properties • 367 contact lens