Spatio-temporal Contrast Sensitivity in the Cardinal Directions of the Colour Space. A Review

Abstract

We review the psychophysics of the spatio-temporal contrast sensitivity in the cardinal directions of the colour space and their correlation with those neural characteristics of the visual system that limit the ability to perform contrast detection or pattern-resolution tasks. We focus our attention particularly on the influence of luminance level, spatial extent and spatial location of the stimuli -factors that determine the characteristics of the physiological mechanisms underlying detection. Optical factors do obviously play a role, but we will refer to them only briefly. Contrast sensitivity measurements are often used in clinical practice as a method to detect, at their early stages, a variety of pathologies affecting the visual system, but their usefulness is very limited due to several reasons. We suggest some considerations about stimuli characteristics that should be taken into account in order to improve the performance of this kind of measurement. RESUMENSe revisa la psicofísica sobre la sensibilidad al contraste con patrones espacio-temporales en las direcciones cardinales del espacio de color y su relación con las características neuronales del sistema visual que limitan la habilidad para realizar una tarea de detección de contraste o de resolución de patrones. La atención se centra especialmente en la influencia del nivel de luminancia, el tamaño y la localización espacial de los estímulos, en la medida que estos son los factores más importantes que determinan las características de los mecanismos fisiológicos que median la detección. Obviamente, los factores ópti-cos también juegan un papel en el conjunto del sistema visual, pero nos referiremos a ellos sólo brevemente. Las medidas de sensibilidad al contraste son a menudo usadas en clínica como método para detectar, en un estado temprano, una amplia variedad de patologías del sistema visual, pero su utilidad en la práctica es bastante limitada por diferentes razones. Sugerimos que ciertas consideraciones sobre los estímulos deberían ser tenidas en cuenta si se quiere mejorar las prestaciones actuales de este tipo de medidas. (J Optom 2010;3:2-19 ©2010 Consejo General de Colegios de Ópticos-Optometristas de España) PALABRAS CLAVE: sensibilidad al contraste; patrones espacio-temporales; espacio de color; direcciones cardinales; caminos visuales. INTRODUCTIONDuring the last three decades, the possibility of early detection of a variety of pathologies affecting the visual system by means of the measurement of spatial and temporal contrast sensitivity functions -CSFs-has been thoroughly explored. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] (Burr D, et al. IOVS 2003;44: ARVO E-Abstract 3193). It has been shown, however, that the usefulness of these functions is rather limited in practice, for several reasons. In the first place, measurements are often limited to the fovea, whilst anatomical damage and functional loss frequently begin outside this region [see, for example, F. Rowe's book 17 ]. In fact, different perimetry technique...

Chromatic Contrast Sensitivity

“…Like any visual contrast, chromatic contrast may occur through variations across space or across time [1]. On the one hand, spatial chromatic contrast consists in the simultaneous occurrence of differ-ences in chromaticity at different locations in space.…”

“…However, these terms highlight different aspects due to their usage in different research domains. On the one hand, the term chromatic contrast mostly (but not exclusively) refers to research on contrast sensitivity and its relation-ship to spatial and temporal frequency [1]. For this reason, the term chromatic contrast focuses on the distribution of color differences across space and time and the ability of the observer to detect these differences (contrast sensitivity).…”

“…Visual acuity is a particular case of spatial resolution, which corresponds to the highest spa-tial frequency that can be detected at maximum contrast [1]. It can only be determined relative to a given contrast, such as the black letters on a white background.…”

“…This index may not only be used for contrast sensitivity measure-ments but also for contrast distributions in scenes. Apart from these three main indices, still other indices to assess contrast are possible [1].…”

6.4: A Computational Color Difference Metric to Evaluate the Viewing Angle Range for FPDs

“…Contrast sensitivity declines rapidly with eccentricity, and the rate of decline increases strongly with spatial frequency [8]. If we use the same set of stimuli to measure the sensitivity at fovea and at a given eccentricity E, we observe the sensitivity shifts towards lower frequencies and sensitivities with increasing E. These changes have been modeled by the eccentricity-adapted scaling factor [9]. We assume that the amount of AF is equal over the azimuth angles.…”