<title>Photolithography for the static compensation of human eye aberrations</title>

Abstract

Recent developments in human eye aberration measurements allow to design and fabricate compensating elements aiming to achieve aberration-limited imaging. This is important not merely from a subject's viewpoint (improving the sharpness of the outer world images formed at the retina) but mainly for clinical instrumentation purposes, especially those dealing with high-resolution retinal imaging (eye fundus cameras, scanning laser ophtlalmosopes, etc). Here we report recent developments in the correction of the static component of the eye aberrations. Aberration data of several subjects were used for manufacturing personally customized phase plates designed to compensate for the wave aberration in the human eye. These plates were made by gray-level single-mask photoscuipture in photoresist and then placed in front of the eye. The effects of misalignments as well as the strategy to design wide-field correcting elements are briefly revised. Applications include improving images in scanning laser ophtalmoscopes. The future plans of research including application of axicons for compensation of the lack of accommodation and kinoforms cancelling high amounts of eye's aberrations in monochromatic illumination are also sketched. MEASUREMENT AND COMPENSATION OF EYE ABERRATIONSRefractive defects of the eye beyond the classical sphero-cylinder ametropies are a subject of growing interest. Recent developments in optoelectronics made possible to build efficient devices to measure and compensate them. Eye aberrations, both monochromatic and polychromatic, are recognized today (together with intraocular scattering) as the main factor limiting the quality of retinal images. Overcoming this limitation should allow for increasing the visual acuity of normal emmetropic subjects beyond the standard 20/20 value. And, perhaps more important than that, compensating eye aberrations will improve the spatial resolution of the eye fundus imaging devices, including retinographic cameras, scanning laser ophthalmoscopes and OCT systems. Improving contrast and resolution is a key factor for successful diagnostics of several ocular diseases in their early stages of development.The basic principles of eye aberration measurement are presently well understood, and the technology required to do it is near reaching maturity. Forty years ago Smirnov[1J described a subjective spatially resolved refractometer built using relatively simple equipment and reported the first -to our knowledge-detailed eye aberration maps. Taking measurements and reducing the raw data was at that time a huge task. Advances in fabrication of narrow-band light sources (lasers and ultrabright LEDs), detectors (APD, CCD, etc) and the widespread availability of computing tools allowed to develop in the last years new aberration measurement devices such as the Howland aberrometers [2-3], improved versions of spatially resolved refractometers [4][5],Hartmann-Shack wavefront sensors [6-8], laser ray-tracing setups [9-12] and pyramidic wavefront sensors [13]. The comprehensive amount o...