| Abstract |
In this study we evaluate and compare the wavefront aberration profiles in single vision and progressive power lenses of different materials and designs, using a Shack-Hartmann wavefront sensor.
Lenses were categorized depending on their material, design and refractive index. Wavefront aberrations were measured using a monochromatic light source (632.8 nm) from an He-Ne laser. Measurements were taken for different points starting from the fitting cross for the progressive lens while from the geometrical centre of the single vision lenses and moving towards the periphery in 10 deg step corresponding to 4mm projection on the lens. Artificial pupils of 3mm and 5mm diameter were used to simulate daytime / mesopic viewing conditions. Lens was shifted around the eye centre of rotation, with a radius of 25 mm, simulating eye's movements. For each point the average of 3 measurements was analysed. Zernike expansion coefficients up to 4th order, sphere, astigmatism, spherical aberration and a range of image quality metrics for each lens were calculated using custom-made scripts in Matlab computational software.
Having created a Microsoft Excel file for each lens with all Zernike coefficients for the different points, the possibility of wavefront reconstruction was feasible. For the two different pupil sizes, wavefront maps were aligned in a matrix, giving a qualitative view of the kind of aberrations that exist at different areas of lenses. Three wavefront maps were created in every case: a) Defocus Sphere, b) Astigmatism and c) All Higher Order Aberrations (3rd & 4th order). In addition, for PPLs, Power Law and vertical astigmatic RMS diagrams were plotted.
The results were compared, contrasted and discussed. Wavefront map analysis offers a qualitative and quantitative evaluation of ophthalmic lens aberrations. In the case of progressive lenses, all suffer from high amounts of astigmatism starting from the near periphery. Modern designs seem to better control higher order aberrations than classic designs and offer enlarged functional vision areas. Pros and cons of hard vs soft design were discussed, showing that for the case of an addition 3.00D PPL, hard designs give wider far and near vision areas. For single vision lenses a significant difference on RMS Z40 between refractive index 1,5 and 1,6 was occurred. Ultimately, examples of occupational single vision lenses were studied showing their ergonomic design.
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Χαρτογράφηση υψηλών εκτροπών σε μονοεστιακούς και πολυεστιακούς οφθαλμικούς φακούς .
