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At least 883 records · Page 49Linked to original sources
PubMed1991

Changes in colour appearance following post-receptoral adaptation.

Current models of colour vision assume that colour is represented by activity in three independent post-receptoral channels: two encoding chromatic information and one encoding luminance. An important feature of these models is that variations in certain directions in colour space modulate the response of only one of the channels. We have tested whether such models can predict how colour appearance is altered by adaptation-induced changes in post-receptoral sensitivity. In contrast to the changes predicted by three independent channels, colour appearance is always distorted away from the direction in colour space to which the observer has adapted. This suggests that at the level at which the adaptation effects occur, there is no colour direction that invariably isolates only a single post-receptoral channel.

Adaptation, Physiological↗
PubMed1995

Quadrant analysis of peripheral colour contrast thresholds can be of significant value in the interpretation of minor visual field alterations in glaucoma suspects.

Peripheral colour contrast thresholds were investigated in glaucoma suspects with no or minor visual field alterations, determining the average colour contrast threshold at 12.5 degrees off axis. The technique was introduced as a rapid screening test for pre-glaucomatous visual loss. Using this 'ring' test, all definite glaucoma patients in the initial study had elevated colour contrast thresholds. In our experience, however, a substantial proportion of early glaucoma patients were found to have normal thresholds. The peripheral colour contrast threshold determined by the ring test is an average threshold in the entire annular zone at 12.5 degrees eccentricity. We therefore modified the test procedure without a major increase in test duration. An arcade subtending 45 degrees at 12.5 degrees eccentricity was used to determine colour contrast thresholds in four quadrants of the visual field separately ('quadrant' test). We present here the first results of this novel procedure, investigating peripheral colour contrast thresholds in glaucomatous patients. The quadrant test is shown to be more sensitive than the ring test in the detection of functional loss.

Adult↗
PubMed1996

Colour contrast thresholds are normal in functional amblyopia.

We evaluated colour contrast thresholds in patients with unilateral functional amblyopia. A computer-controlled colour vision test was used to determine colour contrast thresholds along a blue-yellow tritan axis. Prior to the threshold measurement, a heterochromatic flicker brightness test was performed to ensure isoluminance between the test stimulus and the background for every subject individually. Luminance contrast thresholds were also measured using the same computer-based system. Twenty amblyopic patients were tested. All showed normal tritan colour contrast thresholds both for their amblyopic eye and non-amblyopic fellow eye. Luminance contrast thresholds were elevated in all 6 refractive amblyopic eyes, in 4 of 9 strabismic eyes and in 2 of 5 mixed amblyopic eyes. Colour contrast thresholds are normal in functional amblyopia (with central fixation). Whenever elevated tritan colour contrast thresholds are found in patients with a decreased visual acuity, other causes of visual impairment are to be evaluated.

Adolescent↗
PubMed1999

[Color vision in relation to age: a study of normal values].

BACKGROUND: It is difficult to quantify thresholds in most colour vision tests, and this is especially the case for tritan hues, where a strong age-related increase of threshold has been reported. With the development of computer-graphic methods it is possible to remove brightness clues caused by lens absorption. This study attempts to give normative values for colour contrast thresholds and assess the age related changes therein. PATIENTS AND METHODS: 115 patients aged between 6 & 71 years were tested for central and peripheral colour contrast sensitivity. No patient had any systemic or eye disease. As a preliminary, heterochromatic flicker balance between the luminosities of the R and G and B and G phosphors was established, so that all colours subsequently generated were isoluminant for the person tested. Then, using a modified binary search technique, colour contrast thresholds were established using both 2 degree optotypes, for central vision, and a ring, 12.5 degrees in radius for peripheral vision. In the latter case, the observer had to name the position of the missing quadrant in the ring. Stimuli were presented for 200 msec at 1 Hz. Colours were modulated on protan, deutan or tritan colour axis. RESULTS: No correlation between age and central colour vision thresholds was observed. By contrast a significant but only minor increase of peripheral colour vision threshold was observed for the peripheral protan and tritan axis. DISCUSSION: The present system removes luminance clues from colour vision tests and permits both central and peripheral retina to be tested. The results are simple in that the influence of age can be neglected. The variability of threshold results is small, and it is easy to detect the relatively large changes associated with disease. Since high-quality monitors are standardised and calibrated, providing the stimulus parameters described are adhered to, the results given here for upper limits of normal may be used for other similar systems.

Adolescent↗
PubMed1983

[Examinations of color vision in the differentiation of retinopathia pigmentosa].

Quantitative analyses of color vision using the Farns-worth-Munsell 100-hue test confirm that the mode of inheritance is important for the prognosis of retinopathia pigmentosa. Cases involving the autosomal dominant mode of inheritance are characterized by slight functional losses whereas patients with the autosomal-recessive or the X-chromosomal-recessive mode of inheritance show pronounced defects in the photopic system. With time the degeneration affects the blue, the green and finally the red areas of the color spectrum.

Adolescent↗