Purchase this article with an account.
J. B. Nolan; Color Constancy as Demonstrated by Low Vision Patients and a Subject With a C203R Gene Mutation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3829. doi: https://doi.org/.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
In order to determine the type and numbers of the X-linked pigment genes, a molecular genetic analysis was performed on a subject who exemplified remarkable color constancy ability despite a profound reduction in visual acuity and a lack of effective color vision. For the purpose of exploring how the phenomenological color world of a color vision altered subject who possesses a C203R genetic mutation compares to the color experience of additional clinically diagnosed vision-altered patients exemplifying various forms of color alterations and also in comparison to color normal controls, and to assess whether the sensitivity of receptors will influence one’s description of color, a color naming procedure was utilized.
Our subject (TJ) is a 32 year old male who exemplified 20/160 acuities in both eyes and has been diagnosed with congenital cone dysfunction syndrome. This subject failed all plates in the Ishihara color plate test. Molecular genetic analysis (courtesy of M. Neitz and J. Neitz, Medical College of Wisconsin) was performed on TJ to determine the type and numbers of the X-linked pigment genes. Additional subjects (n=10) had previously been diagnosed with numerous vision conditions resulting in altered forms of color vision. They exemplified best-corrected visual acuities ranging from 20/100 to 20/600 in both eyes. Color vision deficiencies were detected with Ishihara Color Plates). All Subjects and 10 color normal controls were tested using a standard pallet of nominal color regions.
DNA sequencing revealed that subject TJ does not possess a gene that encodes for L photopigment (suggesting that TJ is an obligate protanope).DNA sequencing has also revealed the C203R mutation in a subset of the M genes for TJ.Subject. Data for color naming showed that although the regions chosen by TJ and our other color-altered experimental subjects for the 11 basic color terms were quite large and slightly shifted, they were in rough agreement with control subjects indicating a form of color constancy in this reduced visual acuity, color-altered population.
Despite the fact that TJ exemplifies a C203 mutation of his M pigment genes and other subjects show reduced visual acuity and altered forms of color vision they show consistency in naming colors as well as characteristic shifts and confusions. Thus, results for subject TJ suggest: A very small photoreceptor complement may be sufficient for natural color discrimination and categorization. As such, the present results call into question models of color vision deficiency based on a simple reduction of the available receptoral mechanisms.
This PDF is available to Subscribers Only