On-Screen Deconvolution to Facilitate Computer Access for Users With Visual Impairments
This project explores the possibility of having the computer itself bridge the gap that exists between computer technology (all the benefits that it can provide) and a significant number of individuals suffering from severe eye conditions, such as Keratoconus (with a US prevalence of 1/2000), Pellucid Marginal Degeneration, Terrien's Marginal Degeneration, and related refraction disorders that distort the images perceived by the eye in asymmetrical and irregular ways. The irregularity of the distortion introduced by these conditions is captured by the need to include "higher-order" (i.e., >2) terms in the Zernike polynomial approximation of the eye's "Wavefront Aberration Function" (WA), which represents the distortion of images through the optical components of the eye (cornea, lens). Furthermore, these "higher-order aberrations" are not addressed by traditional mechanisms of vision correction, such as glasses or contact lenses (they usually compensate only for second order Zernike terms, accounting for only defocus i.e., myopia or hyperopia, and the simplest forms of astigmatism, as encoded in the "sphere", "cylinder", and "axis" parameters specified in ophthalmic spectacle prescriptions). This project proposes the use of Point-Spread-Function (PSF), obtained from a person's WA, to pre-compensate (by deconvolution) the images shown on a computer screen, so they are perceived undistorted by the individual whose PSF is considered.
This research introduces a new approach to visual compensation that is, in principle, more general than current optical methods of visual correction, since it naturally accommodates the higher-order components of the visual limitations, not addressed by current solutions. These higher-order effects have an impact on 7,000,000 Americans who have excessively irregular refractive errors, and may partially account for the 14,000,000 Americans who have severe visual conditions not correctable by glasses.
Sponsor: National Science Foundation