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PubMed · 8089039

Generating colour and texture verniers.

G J Brelstaff·J B Wilson
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Abstract

This paper describes computer graphics techniques for presenting visual stimuli in a vernier format composed out of coloured texture patterns. Such stimuli can be used to investigate the performance at the task of localising boundaries mediated by changes in colour and/or texture. We summarise the contents as follows: (1) Techniques for presenting visual stimuli are reviewed with a view to how they might be used to present colour and texture verniers. (2) The design of the vernier stimuli for the localisation task is considered. (3) Significant elements of this design are: (a) the use of non-isoplanatic textures to avoid interference effects at boundaries, (b) the modulation of the texture patterns along axes in MacLeod-Boynton colour space so that relative retinal cone contributions are controlled, and (c) the use of double-buffering, colour map manipulation, and contrast randomisation techniques to avoid problems commonly encountered when presenting computer graphics stimuli on colour monitors. (4) Results of a psychophysical experiment that presents colour and texture verniers are reported elsewhere.

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Color Perception TestsComputer GraphicsHumansPattern Recognition, VisualJournal ArticleResearch Support, Non-U.S. Gov'tReview

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G J Brelstaff, J B Wilson. 1994. Generating colour and texture verniers.. https://doi.org/10.1016/0167-8760(89)90047-0

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Diagnosing protan heterozygosity using the Medmont C-100 colour vision test.

BACKGROUND: A surprisingly high 15 per cent of women in Caucasian societies are carriers of the genes for abnormal colour vision but there is no clinical method to identify them. It has long been known that heterozygotes for the protan colour vision deficiencies can demonstrate a reduced luminous sensitivity to red light. This is known as Schmidt's sign, which is thought to arise from mosaicism (Lyonisation). The Medmont C-100 colour vision test measures relative spectral sensitivity using flicker photometry to differentiate protans and deutans. It should be able to diagnose Schmidt's sign. METHOD: We tested six known protan heterozygotes (four whose sons have a protan colour vision deficiency and two whose fathers are protan) with the Medmont C-100 test. RESULTS: All six heterozygotes made average settings of -1.75 or more negative at the Medmont C-100 test, settings which are at or beyond the boundary of the distribution of settings made by observers with normal colour vision. There have been two previous cases reported in the literature of protan heterozygotes, who made protan settings on the Medmont C-100 or its predecessor test, the OSCAR. We also tested six daughters of the known heterozygotes, 50 per cent of whom are likely to be heterozygotes. Four of the six (66 per cent) made protan settings on the Medmont C-100. The other two made normal 0.0 settings. CONCLUSION: We conclude that the Medmont C-100 can be used clinically to diagnose carriers of protan colour vision deficiency.

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