PubMed · 1497507
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I Adamsons. 1992. Visual function after photorefractive keratectomy.. https://doi.org/10.1001/archopht.1992.01080200021002
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For the rehabilitation of people with impaired vision, it is essential to have adequate (preferably quantitative) information about their residual visual functions. Special attention is given to the extra information provided by the results of measurement of the contrast sensitivity, especially in combination with the results of other measurements, such as the visual field, the amount of intraocular straylight and the visual acuity. The value of the contrast sensitivity function as a predictor of the extent of dysfunctioning in the visual activities of everyday life, such as outdoor vision, reading and recognition of faces, will be discussed. As far as this is concerned, a comparison is made between the value of visual acuity and contrast sensitivity as measures of the extent of vision and visual dysfunctioning.
In this study we investigate the nature of the computations that underlie the encoding of spatial position by the human visual system. Specifically, we explore the relationship between alignment accuracy and spatial scale on the one hand, and between alignment accuracy and contrast on the other. We do this for stimuli where local luminance, local contrast, and orientation cues do not underlie performance. The results suggest that spatial localisation is independent of spatial scale and weakly dependent on contrast. We present subsequent models based on the properties of some classes of visual cortical neurones, namely multiplicative noise and contrast energy detection of complex cells, which describe the form of these relationships.
The spatial frequency tuning of facilitation by masks is derived for a 2 c/deg test grating, counterphased at 8.8 Hz, from the contrasts at which masks of different spatial frequencies facilitate maximally. This tuning function has a bandwidth at half height of roughly 1.5 octaves, much broader than has been estimated previously from tuning functions determined at a constant contrast for each mask. We show also that best facilitation more than doubles sensitivity for tests of 4 c/deg and below, and that the magnitude of the facilitation effect declines at higher spatial frequencies.