Information about Monochromacy
Monochromacy, also known as "total color blindness"[1], is the lack of ability to distinguish colors; caused by cone defect or absence.[2] Monochromacy occurs when two or all three of the cone pigments are missing and color and lightness vision is reduced to one dimension.[1]
Organisms with monochromacy are called monochromats. Monochromats are truly color blind and can see only shades of black, gray and white. The perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by any pure spectral light.
The normal explanation of monochromacy is that the organism's retina contains only a single kind of light receptor cell, or at least that only one kind is active at any particular level of illumination. In vertebrates, which typically have two kinds of receptors, called rods and cones, active at low and higher levels of illumination respectively, there are two main kinds of monochromacy:
In principle there could also be a second kind of cone monochromacy, in which the retina contains no rods, and only a single type of cone. Such an animal would be unable to see at all at lower levels of illumination, but it would have good pattern vision at normal daylight levels (though it would not be able to distinguish hues). In practice it is hard to produce an example of such a retina, at least as the normal condition for a species; there are animals (for example, many birds) with very cone-rich retinas, but they all tend to have multiple types of cones. Some individuals do possess diseases or injuries that lead to nyctalopia, or night blindness, where rod cells stop responding properly to light.
In cone monochromats, at low light intensities the rods and cones may be active simultaneously, allowing some degree of color discrimination. However it is unlikely that this will be functionally significant since the neural apparatus for hue discrimination would presumably not be present in an animal that was monochromatic most of the time.
It used to be confidently claimed that most mammals other than humans and our fellow primates were monochromats. In the last half-century, however, evidence of at least dichromatic color vision in a number of mammalian orders has accumulated. Two of the orders of sea mammals, the pinnipeds (which includes the seal, sea lion, and walrus) and cetaceans (which includes dolphins and whales) clearly are cone monochromats, since the short-wavelength sensitive cone system is genetically disabled in these animals. The same is true of the owl monkeys, genus Aotus.
Both rod and cone monochromacy occur as very rare forms of color blindness in humans. Rod monochromacy, or maskun, is the more common of the two. The majority of people described as color blind, however, are either dichromats or anomalous trichromats.
Monochromacy has been subdivided into typical (rod monochromacy) and atypical forms.[3][4]
Clinically, some monochromats have normal visual acuity and others have poor visual acuity.[5]
The retina is a thin layer of neural cells that lines the back of the eyeball of vertebrates and some cephalopods. It is comparable to the film in a camera.
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Organisms with monochromacy are called monochromats. Monochromats are truly color blind and can see only shades of black, gray and white. The perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by any pure spectral light.
The normal explanation of monochromacy is that the organism's retina contains only a single kind of light receptor cell, or at least that only one kind is active at any particular level of illumination. In vertebrates, which typically have two kinds of receptors, called rods and cones, active at low and higher levels of illumination respectively, there are two main kinds of monochromacy:
- rod monochromacy is the condition of having only rods in the retina. A rod monochromat will be unable to see well in normal daylight levels of illumination.
- cone monochromacy is the condition of having both rods and cones, but only a single kind of cone. A cone monochromat can have good pattern vision at normal daylight levels, but will not be able to distinguish hues. (see below)
In principle there could also be a second kind of cone monochromacy, in which the retina contains no rods, and only a single type of cone. Such an animal would be unable to see at all at lower levels of illumination, but it would have good pattern vision at normal daylight levels (though it would not be able to distinguish hues). In practice it is hard to produce an example of such a retina, at least as the normal condition for a species; there are animals (for example, many birds) with very cone-rich retinas, but they all tend to have multiple types of cones. Some individuals do possess diseases or injuries that lead to nyctalopia, or night blindness, where rod cells stop responding properly to light.
In cone monochromats, at low light intensities the rods and cones may be active simultaneously, allowing some degree of color discrimination. However it is unlikely that this will be functionally significant since the neural apparatus for hue discrimination would presumably not be present in an animal that was monochromatic most of the time.
It used to be confidently claimed that most mammals other than humans and our fellow primates were monochromats. In the last half-century, however, evidence of at least dichromatic color vision in a number of mammalian orders has accumulated. Two of the orders of sea mammals, the pinnipeds (which includes the seal, sea lion, and walrus) and cetaceans (which includes dolphins and whales) clearly are cone monochromats, since the short-wavelength sensitive cone system is genetically disabled in these animals. The same is true of the owl monkeys, genus Aotus.
Both rod and cone monochromacy occur as very rare forms of color blindness in humans. Rod monochromacy, or maskun, is the more common of the two. The majority of people described as color blind, however, are either dichromats or anomalous trichromats.
Monochromacy has been subdivided into typical (rod monochromacy) and atypical forms.[3][4]
Clinically, some monochromats have normal visual acuity and others have poor visual acuity.[5]
Cone monochromacy
Cone monochromacy is a rare, total color blindness that is accompanied by relatively normal vision, electoretinogram, and electrooculogram.[2] There are three types named according to the single functioning cone class:- Blue cone monochromacy, also known as S-cone monochromacy[1]
- Green cone monochromacy, also known as M-cone monochromacy[1]
- Red cone monochromacy, also known as L-cone monochromacy[1]
References
1. ^ "Guidelines: Color Blindness." Tiresias.org. Accessed September 29, 2006.
2. ^ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
3. ^ Alpern M. "What is it that confines in a world without color?" Invest Ophthalmol. 1974 Sep;13(9):648-74. PMID 4605446.
4. ^ Hansen E. "Typical and atypical monochromacy studied by specific quantitative perimetry." Acta Ophthalmol (Copenh). 1979 Apr;57(2):211-24. PMID 313135.
5. ^ [1]
6. ^ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
2. ^ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
3. ^ Alpern M. "What is it that confines in a world without color?" Invest Ophthalmol. 1974 Sep;13(9):648-74. PMID 4605446.
4. ^ Hansen E. "Typical and atypical monochromacy studied by specific quantitative perimetry." Acta Ophthalmol (Copenh). 1979 Apr;57(2):211-24. PMID 313135.
5. ^ [1]
6. ^ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
See also
Color vision |
|---|
Color vision - Color blindness - Opponent process
Monochromacy - Dichromacy - Trichromacy - Tetrachromacy - Pentachromacy
|
Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
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visible spectrum (or sometimes optical spectrum) is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light.
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- For the moth genus, see Retina (moth).
The retina is a thin layer of neural cells that lines the back of the eyeball of vertebrates and some cephalopods. It is comparable to the film in a camera.
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Location Retina
Function Low light photoreceptor
Morphology rod shaped
Presynaptic connections None
Postsynaptic connections Bipolar Cells and Horizontal cells
Rod cells, or rods
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Function Low light photoreceptor
Morphology rod shaped
Presynaptic connections None
Postsynaptic connections Bipolar Cells and Horizontal cells
Rod cells, or rods
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Cone cells, or cones, are photoreceptor cells in the retina of the eye which function best in relatively bright light. The cone cells gradually become more sparse towards the periphery of the retina.
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Achromatopsia
Classification & external resources
ICD-10 H 53.5
ICD-9 368.54
OMIM 216900 262300 139340
DiseasesDB 83
MeSH D003117
Achromatopsia (ACHM) is the inability to see color.
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Classification & external resources
ICD-10 H 53.5
ICD-9 368.54
OMIM 216900 262300 139340
DiseasesDB 83
MeSH D003117
Achromatopsia (ACHM) is the inability to see color.
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Hue is one of the three main attributes of perceived color, in addition to lightness and chroma (or colorfulness). Hue is also one of the three dimensions in some colorspaces along with saturation, and brightness (also known as lightness or value).
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Nyctalopia
Classification & external resources
ICD-10 H 53.6
ICD-9 368.6
Nyctalopia (Greek for "night blindness") is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases.
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Classification & external resources
ICD-10 H 53.6
ICD-9 368.6
Nyctalopia (Greek for "night blindness") is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases.
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Mammalia
Linnaeus, 1758
Subclasses & Infraclasses
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Linnaeus, 1758
Subclasses & Infraclasses
- Subclass †Allotheria*
- Subclass Prototheria
- Subclass Theria
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Primates
Linnaeus, 1758
Families
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Linnaeus, 1758
Families
- 15, See classification
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Dichromacy in humans is a moderately severe color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, predominantly affecting males.
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order (Latin: ordo, plural ordines) is a rank between class and family (termed a taxon at that rank). The superorder is a rank between class and order. Exact details of formal nomenclature depend on the Nomenclature Code which applies.
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Pinnipeds ("fin-feet", lit. "winged feet") are marine mammals belonging to the former biological suborder Pinnipedia (sometimes now a superfamily) of the order Carnivora. The pinnipeds now fall within the suborder Caniformia and comprise the families Odobenidae (walruses),
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Cetacea
Brisson, 1762
Diversity
Around 88 species; see list of cetaceans or below.
Suborders
Mysticeti
Odontoceti
Archaeoceti (extinct)
(see text for families)
The order Cetacea
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Brisson, 1762
Diversity
Around 88 species; see list of cetaceans or below.
Suborders
Mysticeti
Odontoceti
Archaeoceti (extinct)
(see text for families)
The order Cetacea
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Aotidae
Poche, 1908 (1865)
Genus: Aotus
Illiger, 1811
Type species
Simia trivirgata
Humboldt, 1811
Species
Aotus lemurinus
Aotus hershkovitzi
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Poche, 1908 (1865)
Genus: Aotus
Illiger, 1811
Type species
Simia trivirgata
Humboldt, 1811
Species
Aotus lemurinus
Aotus hershkovitzi
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Achromatopsia
Classification & external resources
ICD-10 H 53.5
ICD-9 368.54
OMIM 216900 262300 139340
DiseasesDB 83
MeSH D003117
Achromatopsia (ACHM) is the inability to see color.
..... Click the link for more information.
Classification & external resources
ICD-10 H 53.5
ICD-9 368.54
OMIM 216900 262300 139340
DiseasesDB 83
MeSH D003117
Achromatopsia (ACHM) is the inability to see color.
..... Click the link for more information.
Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
..... Click the link for more information.
..... Click the link for more information.
Dichromacy in humans is a moderately severe color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, predominantly affecting males.
..... Click the link for more information.
..... Click the link for more information.
Trichromacy is the condition of possessing three independent channels for conveying colour information, derived from the three different cone types.[1] Organisms with trichromacy are called trichromats.
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Visual acuity (VA) is acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye, the sensitivity of the nervous elements, and the interpretative faculty of the brain.
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A cone dystrophy is an inherited ocular disorder characterized by the loss of cone cells, the photoreceptors responsible for both central and color vision.
The most common symptoms of cone dystrophy are vision loss (age of onset ranging from the late teens to the sixties),
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The most common symptoms of cone dystrophy are vision loss (age of onset ranging from the late teens to the sixties),
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Achromatopsia
Classification & external resources
ICD-10 H 53.5
ICD-9 368.54
OMIM 216900 262300 139340
DiseasesDB 83
MeSH D003117
Achromatopsia (ACHM) is the inability to see color.
..... Click the link for more information.
Classification & external resources
ICD-10 H 53.5
ICD-9 368.54
OMIM 216900 262300 139340
DiseasesDB 83
MeSH D003117
Achromatopsia (ACHM) is the inability to see color.
..... Click the link for more information.
Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect or emit. The nervous system derives color by comparing the responses to light from the several types of cone photoreceptors in the eye.
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Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
..... Click the link for more information.
..... Click the link for more information.
opponent process is a color theory that states that the human visual system interprets information about color by processing signals from cones and rods in an antagonistic manner.
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Dichromacy in humans is a moderately severe color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, predominantly affecting males.
..... Click the link for more information.
..... Click the link for more information.
Trichromacy is the condition of possessing three independent channels for conveying colour information, derived from the three different cone types.[1] Organisms with trichromacy are called trichromats.
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Tetrachromacy is the condition of possessing four independent channels for conveying color information, or possessing four different cones, one other than RGB. Organisms with tetrachromacy are called tetrachromats.
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Pentachromacy is the condition of possessing five independent channels for conveying color information. Organisms with pentachromacy are called pentachromats. For these organisms, the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a
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Herod_Archelaus
