Simulating images seen by patients with inhomogeneous sensitivity losses

We aim to simulate how colored images are perceived by subjects with local achromatic and chromatic contrast sensitivity losses in the visual field (VF).

The spatiochromatic corresponding pair algorithm, introduced in a previous article (J Opt Soc Am (A) 2004;21:176-186), has been implemented with a linear model of the visual system. Spatial information is processed separately by the chromatic and achromatic mechanisms by means of a multiscale model, with sensors selective to frequency, orientation, and spatial position, whose mechanism-dependent relative weights change with the spatial location of the image. These weights have been obtained from perimetric data from a patient with Leber's Hereditary Optic Neuropathy and an age-matched sample of normal subjects, using achromatic, red-green, and blue-yellow gratings of different spatial frequencies. Distortion contours for each mechanism have been derived from the images simulating the perception of these subjects at different locations in the VF.

The images simulating the perception of normal subjects at different locations of the VF show a fast decrease in image quality with eccentricity. The same analysis carried out with the Leber's Hereditary Optic Neuropathy patient reveals worse overall image quality throughout the VF, plus a color vision defect resembling red-green dichromacy at fovea and trichromatic anomaly in the rest of the VF.

In the present article, we show that implementing the algorithm with a spatial vision model that considers the changes in contrast sensitivity with spatial location of the stimulus may reveal the local effects that are suffered, in general, by pathological subjects, and that are ignored by simpler spatial vision models.