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Topic: Colour blindness

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	Tiresias - Guidelines (User Groups: Visual Impairment - Colour Blindness)
		Colour blindness is the reduced ability to distinguish between certain colours or wavelengths of light.
		Colour blindness is normally diagnosed through clinical testing and a number of tests have been devised.
		The most common, hereditary colour blindnesses are known as red-green colour vision deficiencies, they are associated with disturbances in either the L-cone photopigment (protan defects, with protanomaly being the alteration form and protanopia being the loss form) or M-cone photopigment (deutan defects, with deuteranomaly being the alteration form and deuteranopia being the loss form).
	www.tiresias.org /guidelines/colour_blindness.htm (1093 words)

	theories
		One method for identifying the colour discrimination abilities of dichromats is to plot on the CIE chromaticity diagram the pair of colours confused.
		Colour matching involves the adjustment of one to three light sources so that the test stimuli produced matches the colour appearance of an adjacent comparison stimulus.
		Colour deficient arrangements result in crossovers on the hue circle; the orientation of the axis of the crossover (i.e., deutan, tritan or protan) indicates the type of colour deficiency.
	psychology.ucalgary.ca /pace/VA-Lab/colourperceptionweb/congenital.htm (2338 words)

	Anomalous Colour Vision
		This, besides being unfair, shows that the commonest varieties of colour blindness are congenital, due to genetic differences in the sex-determining Y chromosome (where some genes are not duplicated), and that colour blindness is a recessive characteristic, like haemophilia.
		Colour blindness can also be the result of disease or poisoning, where it has no genetic basis, or due to other faults than those of the visual proteins.
		The perception of colour is not entirely that exhibited under standard laboratory conditions, as in the assessment of anomalous colour vision, but in nature is influenced by illumination, contrast, fatigue and other factors.
	www.du.edu /~jcalvert/optics/colvisn.htm (1374 words)

	Colour blindness - Better Health Channel.
		The mother is not herself colour blind because the gene is recessive.
		Many people with red–green colour blindness will be able to get a car driver's licence, but may not qualify for a commercial driver's licence, or they may have restrictions which mean they cannot drive at night.
		Colour blindness is caused by a lack of particular colour-sensitive cells in the back of the eye.
	www.betterhealth.vic.gov.au /bhcv2/bhcarticles.nsf/pages/Colour_blindness?open (954 words)

	Joe's Astro-Photo Page // Colour Blindness & Amature Astronomy
		Since colour blindness is not treatable or cureable in any conventional sense, little attention is paid to it by the medical community.
		In colour blindness, it may be that a person has more rods than cones, it it may be that the cones are not fully functional - depends on the individual and the specific form of colour blindness.
		Ther stronger the colour is in an object being observed - whether it is a comet or a globular or a nebula, the birghter it appears.
	www.start.ca /users/joneil/colour.html (1355 words)

	AboutKidsHealth: Health A-Z: Colour Blindness (Site not responding. Last check: 2007-09-10)
		Colour blindness is a vision problem that makes it hard to tell the difference between certain colours.
		Colour blindness is usually an inherited and lifelong condition.
		A colour blind child will not be able to see the number because it will appear as the same colour as the other circles on the page.
	www.aboutkidshealth.ca /Article.asp?articleID=1869 (579 words)

	Colour blindness
		Colour blindness can be due to a lack of one of the three types of cones, or be due to differences in the pigments in the cones.
		This is because colour blindness is hereditary and the gene that leads to colour blindness is located on the X-chromosome.
		Women who are carriers of one gene for colour blindness, and who therefore are not colour blind, can still hand the gene on to their children (in 50% of the cases).
	www.capioeye.co.uk /eyeinfo/colourvision (712 words)

	BBC - h2g2 - Colour Blindness - A883523
		Colour blindness is a disorder in which the individuals affected have a partial or total inability to detect certain wavelengths of the visual spectrum.
		Colour blindness varies between individuals in both the insensitivity and the wavelengths they are unable to see.
		Colour blind people have a tendency to better night vision and an ability to be able to distinguish hues that remain unseen to those who do not have the disorder
	www.bbc.co.uk /dna/h2g2/alabaster/A883523 (1840 words)

	Colour Blindness
		Colour deficient grandfathers pass the trait on to non-affected daughters who pass it on to grandsons.
		Colour perception is the process of distinguishing varying ways in which points or homogeneous patches of light appear to a subject.
		Complete colour blindness affects fewer than three people in a million and is usually associated with a variety of other serious problems with vision.
	www.cdli.ca /d6vsatf2000/s12/Project1/blindness.htm (682 words)

	Colour
		Colour is simply light of different wavelengths and frequencies and light is just one form of energy made up from photons.
		As the light passes through the prism, it is split into the seven visible colours of the spectrum by refraction.
		The higher the frequency, of the colour, the closer together the waves of energy are.
	www.colourtherapyhealing.com /colour (741 words)

	BBC NEWS \| Health \| Colour blindness cell loss clue
		People with colour blindness for one reason or another are unable to process these light signals in the usual way because their cones are unable to distinguish properly between colours, such as red and green.
		In this form of colour blindness the person is missing one of the three pigments needed to distinguish between colours.
		Until now, it was unclear whether individuals with dichromatic colour blindness had the normal number of cones, but just two types instead of three, or simply lacked a particular type of cone, and consequently had fewer cells to make sense of light signals.
	news.bbc.co.uk /1/hi/health/3720841.stm (542 words)

	BBC - Health - Mens health - Colour blindness
		Colour blindness is the reduced ability to distinguish between certain colours.
		If you're colour blind, you won't be able to see these colours and so you won't be able to pick out the pattern from the dots.
		Colour blindness needn't stop someone driving, because traffic lights can be distinguished by the position of the light.
	www.bbc.co.uk /health/mens_health/issues_colour.shtml (525 words)

	Colour Blind Test and Colour Deficiency Eye Test
		The cones don't directly report on the colours received, but rather interact with other circuits in the brain, so that certain signals are 'added' together, and others are 'subtracted' from each other.
		Most colour blindness involves red or green, and is hereditary via the X chromosome, and hence affects men more frequently than women.
		In an anomalous trichromat, the colour reception of the green cones is shifted towards the red end of the spectrum, to a greater or lesser degree; or else the reception of the red cones is shifted towards the green part of the spectrum.
	www.spectacleworld.co.za /colour-blind.htm (627 words)

	The Genetics Of Colour Blindness
		One of the traits in question is colour blindness, a condition in which a person is unable to distinguish colours, particularly red and green, easily distinguished by a person with normal vision.
		Colour blindness is a recessive trait with respect to normal vision, which is the dominant trait.
		Half of all the sons will inherit the X chromosome with the gene for colour blindness from their mother, and will consequently be colour-blind (c); the other half of the male offspring will inherit the gene for normal vision (C).
	www.stemnet.nf.ca /d6vsatf2000/s12/Project1/genetics.htm (493 words)

	Colour Blindness - Search Results - MSN Encarta (Site not responding. Last check: 2007-09-10)
		Colour Blindness, defect of vision affecting the ability to distinguish colours, occurring mostly in males.
		Colour is also produced in other ways than by absorption of light.
		The colours of mother-of-pearl and of soap bubbles are caused by interference....
	uk.encarta.msn.com /Colour_Blindness.html (146 words)

	Colour blindness
		Colour blindness is an inaccurate term for a lack of perceptual sensitivity to certain colors.
		Absolute colour blindness is almost unknown, but in very rare cases, total colour blindness occurs.
		Affecting around 7% of men and around 0.04% women, the main form of colour blindness is the inability to distinguish red from green.
	www.colourtherapyhealing.com /colour/colour_blindness.php (305 words)

	EveryEye: colour blindness
		Full colour vision relies on the smooth operation of 3 types of cell that are sensitive to colour light: blue, red and green cone receptors.
		One very rare form of colour blindness is achromatopsia, in which none of the colour receptors are functioning.
		If the colours are not carefully chosen they will not achieve their intended purpose when viewed by colour-blind users making your site harder and less pleasant to use.
	www.everyeye.co.uk /htms/colourblindness.htm (313 words)

	[No title]
		Colour blindness comes as a result of a lack of one or more of the types of colour receptors.
		Red-green colour blindness is a result of a lack of red receptors.
		Another form of colour blindness -- yellow-blue is the second most common form, but it's extremely rare.
	www.digitalexposure.ca /BlindTest.html (137 words)

	The Human Side of Colour Blindness ( Color Blindness )
		When someone is colour blind then, they might see two colours really good, one colour really good, they might be 90% red, 90% green, 20% blue, or they might be 25% red, 45% green and 85% blue, or any number of combinations.
		Ten percent of the male population and around 0.5% of the female population in Canada and the USA are said to be colour blind.
		The main point however is colour blindness is something a person can go through their entire life with, and never be noticed, even by caring people and even if it is a more severe form of the condition.
	www.start.ca /users/joneil/colour2.htm (3871 words)

	[No title]
		Defective colour vision, commonly known as colour blindness, is a serious issue which affects the life and work of approximately 1 in 12 men and 1 in 200 women.
		The epidemic of blindness takes place without any apparent cause; the disease spreads quickly and as the novel ends the blind are getting their vision back.
		One view proposes that blind individuals are severely impaired because vision is so essential in the development of spatial concepts.
	www.lycos.com /info/blindness--vision.html (519 words)

	Colour Blind Resource Centre - How do you get colour blindness?
		Colour blindness is a sex linked recessive condition, which all you biology buffs know means that it is a recessive trait condition which is transmitted in the 23 pair of chromosomes.
		As I mentioned before, colour blindness is a recessive trait which is transmitted via X chromosomes in the 23rd pair of chromosomes.
		Because males have only one X chromosome in their 23rd pair, they have a higher chance of inheriting colour blindness, this is why more males in the population have colour blindness then females.
	colourblind.freeservers.com /how.htm (499 words)

	The Production of Colour Teaching Materials and Colour Blindness
		Colour blind persons may have one or more receptors missing or more frequently the receptor responses are less separated so that colour differences cannot be perceived or can only be seen with great difficulty.
		This means that if a red green colour blind person perceives two colours to have the same brightness they will not be able to distinguish between them, unless the blue receptor is stimulated differently, eg 'yellow and bright green' have a similar 'blue' content so will appear as the same tone of grey.
		Colours that differ greatly in luminance will be able to be readily distinguished from each other by colour blind as well as normal sighted viewers.
	www.city.ac.uk /colourgroup/colourblind.html (641 words)

	Color Blindness: More Prevalent Among Males
		This is the commonest form of color blindness, but it affects only.4 percent of women.
		The fact that color blindness is so much more prevalent among men implies that, like hemophilia, it is carried on the X chromosome, of which men have only one copy.
		Because the DNA sequences of the red and green receptor genes are so similar, and because they lie head to tail, it is easy for mistakes to occur during the development of egg and sperm, as genetic material is replicated and exchanged between chromosomes.
	www.hhmi.org /senses/b130.html (602 words)

	Color Blindness Test for Children - Keep Kids Healthy
		Color vision defects (dyschromatopsia), often called color blindness, are a common problem, and it is estimated that 4% of people have problems with their color vision.
		Defects can range from total color blindness (complete achromatopsia), which is rare, to just having problems confusing colors, like blues and violets, red and brown, green and brown, green and gray, green and white, blue and purple, red and yellow, or red and green.
		In school, being color blind can cause difficulty if teachers are using colors to represent things that they are trying to teach your child and he can't tell the difference between the colors.
	www.keepkidshealthy.com /development/color_blindness.html (655 words)

	Colour blindness sometimes an advantage (Site not responding. Last check: 2007-09-10)
		The researchers had deuteranomalous and "colour-normal" individuals to rate the differences between pairs of colours that were predicted by the researchers to look different to those with colour blindness but the same to those with normal colour perception.
		All humans have some form of colour blindness as the human eye is unable to distinguish all the physical variations in the light reflected to us from surfaces.
		Men who are colour blind have the three cones but one has a peak sensitivity shifted from the common position in the spectrum.
	www.admin.cam.ac.uk /news/dp/2005121402 (250 words)

	Colour Blindness
		Colour blindness results from an absence or malfunction of certain colour-sensitive cells in the retina.
		The term “colour vision problem” is often used instead of colour blindness because most people with colour blindness can see some colour.
		The type of colour vision problem you have can often be determined by which patterns you can and can't see in the various plates used for the test.
	www.bchealthguide.org /kbase/topic/mini/hw143997/overview.htm (603 words)

	About Color Blindness - What, why, how - problems
		Color blindness (color vision deficiency) is a condition in which certain colors cannot be distinguished, and is most commonly due to an inherited condition.
		Those who are not color blind seem to have the misconception that color blindness means that a color blind person sees only in fl and white or shades of gray.
		Color blindness is a malfunction of the retina, which converts light energy into electircal energy that is then transmitted to the brain.
	www.toledo-bend.com /colorblind/aboutCB.html (1945 words)

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