Cortical color blindness, or cerebral achromatopsia, has been likened by some authors to "blindsight" for color or an instance of "covert" processing of color. Recently, it has been shown that, although such patients are unable to identify or discriminate hue differences, they nevertheless show a striking ability to process wavelength differences, which can result in preserved sensitivity to ch...

In this chapter, we introduce the molecular structure of the genes encoding the human cone photopigments and their expression in photoreceptor cells. We also consider the consequences that alterations in those genes have on the spectral sensitivity of the photopigments, the cone photoreceptor mosaic, and the perceptual worlds of the color normal and color blind individuals who possess them. Thr...

The mother or daughter of a male with an X-chromosome-linked red/green color defect is an obligate carrier of the color deficient gene array. According to the Lyonization hypothesis, a female carrier's defective gene is expressed and thus carriers may have more than two types of pigments in the L/M photopigment range. An open question is how a carrier's third cone pigment in the L/M range affec...

Red-green color vision is strongly suspected to enhance the survival of its possessors. Despite being red-green color blind, however, many species have successfully competed in nature, which brings into question the evolutionary advantage of achieving red-green color vision. Here, we propose a new method of identifying positive selection at individual amino acid sites with the premise that if p...

PURPOSE To investigate the influence of color vision on myopia development by testing refraction error and axial length of the eye for high school students with and without color vision deficiency (CVD). METHODS A school-based cross-sectional, cluster sample study was conducted to test the color vision and refractive error of 16,539 high school students. Students were screened for CVD using a...

Both acquired color vision deficiencies and abnormal pattern electroretinograms (PERGs) are observed in patients with ocular hypertension (OHT) as well as in patients with glaucoma. In the present study we determined the prevalence of both of these functional deficits in a large group of OHT patients (N = 130). Color vision was tested with the desaturated D-15 and a color confusion score was us...

OBJECTIVE To investigate the prevalence of red-green color vision deficiency (CVD) among medical and dental students compared with non-medical students. METHODS This descriptive, cross-sectional study compared the prevalence of CVD between medical and non-medical Pakistani students. A total of 926 medical and dental students from Baqai Medical University, Karachi, Pakistan were compared with ...

This paper presents a new approach including passive and actrive processes to deal with the image segmentation and pattern recognition to a color blindness plate (CBP). The CBP is well-known satisfactory way of testing the degree of color blindness happened in the human visual system. The image of CBP is very complex. It includes not only the colors but also the disconnected size-varied dots. I...