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Impairment of visual functions
Published in Ramar Sabapathi Vinayagam, Integrated Evaluation of Disability, 2019
Normal persons (trichromats) are sensitive to red, green, and blue light. Dichromats, with two photoreceptors, can recognize two colors. Most of the dichromats are red and green color deficient. Yellow and blue color deficient persons are rare. Monochromats with a single photoreceptor are color blind as they cannot recognize any color signal. They perceive only grayscale between black and white. Persons with achromatopsia (13) (monochromats) are deprived of the full experience of color perception in their environment, and this may interfere with activities of daily living. They also find it difficult to identify the color signal in a traffic light, and can drive only by locating the illumination of upper, middle, or lower lights. Thus, they have the risk of being involved in an accident. Furthermore, color discrimination is significantly important in certain occupations requiring critical safety tasks, such as in air, marine, road, and train transport systems as well as in certain trades. Hence, they may not be eligible for occupations such as a pilot, train engineer, railroad worker, firefighter, and signalman on railways. In dichromatopsia and those with anomalous color vision, there is an inaccurate recognition of the actual color and the perception of the reduced intensity of color may further augment the difficulty in identifying standard colors at a regular distance or in the presence of mist, smoke, or during rain. Thus, the quality of life is at a low ebb in persons with impairment of color vision.
Comparative Study of the Primate Retina
Published in Jon H. Kaas, Christine E. Collins, The Primate Visual System, 2003
The one-to-one connection between M/L cones, midget bipolar, and P ganglion cells, which constitute the basis for red-green color opponency of trichromatic primates was first described in catarrhines.2,43 Thus, it is of considerable importance to address the question of whether dichromatic platyrrhines or the monochromatic Aotus also have such a circuit, despite lacking red-green color-opponency. To answer this ques-tion, bipolar cells were labeled with Dil retinal implants and ganglion cells were labeled by retrograde transport of Biocytin.4445× It was found that the central retina of dichromatic Cebus and monochromatic Aotus preferentially had single-cone MB bipolar cells (Figure 2.2A), and that these cells had axon terminals whose sizes are in the range of the dendritic tree sizes of central P ganglion cells. These findings suggested that one-to-one connections between M/L cones, midget bipolar cells, and P ganglion cells are a feature of the P pathway shared by diurnal catarrhines, diurnal platyrrhines, and nocturnal platyrrhines, independently of the presence of one or two M/L-cone photo-pigments in their retina. They are consistent with the hypothesis that the P pathway evolved for achromatic vision before red-green color opponency appeared.31
Nutrition and the Cancer Patient
Published in David Heber, Zhaoping Li, Primary Care Nutrition, 2017
We are now separated from the system that enabled us to select foods according to color and taste. Humans and a few primate species have trichromatic color vision, so that they are able to distinguish red from green (Dominy and Lucas 2001). All other mammals have dichromatic vision and cannot distinguish between the two colors. One hypothesis for the evolution of this visual ability was that it conferred an advantage by enabling primates to distinguish red fruits from the green background of forest leaves. We could joke that today colors are still used to promote food choices, as most fast-food restaurants package their beige french fries in a red cardboard package. Contrasting colors have been shown to be one of the key factors in food selection by Drewnowski (1996). A new method for selecting fruits and vegetables based on colors keyed to the content of phytochemicals is described as a way of translating the science of phytochemical nutrition into dietary guidelines for the public. Most Americans eat only two to three servings of fruits and vegetables per day, without regard to the phytochemical contents of the foods being eaten. Certain phytochemicals give fruits and vegetables their colors and also indicate their unique physiological roles. All the colored phytochemicals that absorb light in the visible spectrum have antioxidant properties. In artificial membrane systems, it is possible to show synergistic interactions of lutein and lycopene in antioxidant capacity, and there are well-known antioxidant interactions of vitamins C and E based on their solubility in hydrophilic and hydrophobic compartments of cells.
Wheel-running activity rhythms and masking responses in the diurnal palm squirrel, Funambulus pennantii
Published in Chronobiology International, 2020
Dhanananajay Kumar, Sanjeev Kumar Soni, Noga Kronfeld-Schor, Muniyandi Singaravel
The family Sciuridae differs from the other Rodentia families in that it is mainly diurnal. Furthermore, within the family Sciuridae, the subfamily Sciurinae, which includes the arboreal and terrestrial squirrels, is an entirely diurnal subfamily (Roll et al. 2006). Sciuridae was among the first taxa to evolve diurnality, at about the same time as the infraorder Simiiformes (monkeys and apes) (Maor et al. 2017), which suggests they had the opportunity to evolve comparable visual adaptations to diurnality. This is consistent with their evolution of adaptations to diurnal activity, including cone dominated retinas, large numbers of blue and green cones that mediate excellent dichromatic color vision, and more (Van Hooser & Nelson 2006). It is possible that the long evolutionary time of diurnality also resulted in a more stable and robust diurnal circadian system, compared to other diurnal rodent species that developed diurnality later. Therefore, studying Sciuridae’s circadian system may contribute significantly to our understanding of the mammalian switch to diurnality and the circadian system of diurnal species.
Dalton's pseudo‐isochromatic plates and congenital colour vision deficiency
Published in Clinical and Experimental Optometry, 2020
Anuradha Narayanan, Mohan Venkadesan, Sruthi Sree Krishnamurthy, Jameel R Hussaindeen, Krishna Kumar Ramani
The colours were selected based on the red‐green dichromatic lines of confusion for protans and deutans in the 1931 XYZ chromaticity diagram. Luminance noise was added to reduce luminous contrast clues in the figures. The XYZ values were transformed into the International Commission on Illumination (CIE) L*a*b* co‐ordinates and used by Corel Draw X7 application software's colour matching and setting tool to check to ensure that the co‐ordinates fell within the colour gamut of the inks and then transform the CIE L*a*b* values into CMYK values for printing. During the printing process, the consistency of the colour stimuli was provided by means of International Color Consortium colour management system which was inbuilt with the printer. The quality of the printed images was assessed using the CIE L*a*b* space with white reference: American National Standards Institute T ‘absolute white’ under ISO 12647‐2 printing standard. The plotting of the hues for the foreground and background are provided in Figures 1 and 2.
The effect of the ChromaGen contact lens system on visual performance
Published in Clinical and Experimental Optometry, 2020
Cagri Ilhan, Mehmet A Sekeroglu, Sibel Doguizi, Pelin Yilmazbas
Despite the limited benefits of CCLs in patients with protan defects, all CCLs equally (Violet 3 included) improved the mean number of recognised symbols in patients with deutan defects. Swarbrick et al.2001 reported there was no difference in the number of recognised symbols between a normal trichromat and a dichromat after the insertion of CCLs in eyes with deutan defects. Similarly, in the present study, while the number of recognised symbols was lower in patients with medium rather than strong deutan defects at baseline, the numbers of recognised symbols of the two groups were similar after the insertion of CCLs. This study analysed the results in detail according to the type and extent of congenital red‐green CVD.