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» Hatrack River Writers Workshop » Forums » Open Discussions About Writing » Vision anomalies

   
Author Topic: Vision anomalies
Silver3
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Does anyone around here know about the way the eye works?

I need my character to have some form of colour-blindness; is there some form of that which shows in the colour/external aspect of the eye (so that people would know on looking at him that he has vision problems)? The article I found on Wikipedia is great for technical stuff, but it doesn't really tell me much on the practical side.

Thanks in advance


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tchernabyelo
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I'm not aware of any form of colour-blindness that would be visible to others.

The only visual conditions I can think of that would be obvious to other people are things like cataracts. I guess there might be some way in which a coloured catarct could develop, meaning that someone couldn't see a particular colour, or distinguish some range of colours, but I don't know of an instance.


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Silver3
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Damn. I'll just have to make one up, then
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tchernabyelo
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Well, if you're writing fantasy, you can easily come up with a condition like (say) yellow cataracts, that sort of have the effect of wearing permanent sunglasses.

If it isn't fantasy, then you may have to work harder at rationalising it.


I could be wrong; there are doubtless people on here who know a lot more about ophthalmology than I do.


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Silver3
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We were talking fantasy
I just wanted to see whether there was something real that I could use, or whether I needed to be a little more creative.

Thanks !


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Calligrapher
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Have the character wear wild colored, mix-matched clothing. Other characters could comment he must be color blind.
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quidscribis
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Cataracts, in their early stages, are not visible. Later on, when vision is greatly impaired, it's visible as a whitening of the pupil.

However, cataracts do not affect color as far as I know.

The only differences I've noticed thus far is that it's more difficult to focus, and that gets worse as the cataracts become worse, and a cloudy feeling, like a film over the eye making everything more difficult to see.

I'm still in the early stages.

Edit to add: Ooops. Misinterpreted that post up there. Must be blindness setting in from the cataracts. :P Yes, if you created a type of cataracts that had a colored film instead of white, then you could induce color blindness of a type.

[This message has been edited by quidscribis (edited January 18, 2006).]


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Jeraliey
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Jaundice is easily seen, and it tinges vision yellow...it's a full-body thing, though. You could modify it so it's concentrated in the eyes or something, as long as we're doing fantasy

Alternatively, you could have your character's pupils be permanently constricted, almost to pinpoints, which would not let in enough light to allow him/her to distinguish colors.


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pantros
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Albino people are frequently color blind.

There are bits of the retina that some color blind people do not have - thus causing their color blindness.


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RedSakana
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Even achromatopsia (complete lack of cones, resulting in no color vision whatsoever) isn't externally visible--certainly the more common red-green colorblindness can't be detected just by looking at someone's eyes.

I'm not sure that the yellow cataracts that other people have been suggesting would produce the effect that you want. If everything a person sees is shifted to look more yellow, they will still be able to see and distinguish between different wavelengths of light. For example, my sunglasses have a yellowish tinge to them, but I have no trouble at all identifying various colors. In fact, my brain will compensate for the yellow tinge, to the point where when I remove the sunglasses, the colors look a bit off at first (but I can still distinguish between them).

What sort of color impairments does your character need to have? An in ability to distinguish between two colors? Complete lack of color vision?

Anyway, the only way that I can think of to link colorblindness with an external trait would be to have the particular type of colorblindness that the character has be very rare--only found in a very isolated population, and then have that same population have distinctive eye color. Oliver Sacks wrote about someting along these lines in Island of the Colorblind. Aparantly on this island there is a very high incidence of achromatopsia, and also a high incidence of near-sightedness. The two turn out to be unrelated, but since the population on the island was small and isolated, there were a lot of people that were both colorblind and near-sighted.


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Survivor
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There is also the case where color-blindness is the inheritance of a specific lineage, and thus might be seen often in combination with another trait from that ancestor.

To be more specific, let's say you have a population of Pacific islanders who have very little color-blindness. One day a single color-blind Dutchman with blue/grey eyes becomes stranded on the island, and settles there. If no further sources of color-blindness or blue eyes are introduced into the population, then within a couple of generations it will be commonplace for blue eyes to be associated with color-blindness, even if there isn't a perfect correlation either way.

Again, something that might work for a fantesy or other non-contemporary setting. But in a contemporary setting, there isn't really any way to know that people are color-blind unless they take a test designed to determine their ability to see different colors.


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abby
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Since its fantasy, do the obvious: with "type" of color blindness the person wears "color" of contacts to counter act the color blindness so they can see normal.
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RedSakana
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quote:
Since its fantasy, do the obvious: with "type" of color blindness the person wears "color" of contacts to counter act the color blindness so they can see normal.

Unfortunately, this won't actually work to treat colorblindness--the problem involves receptors (in the eye) for a specific wavelength (color) of light. Colored contacts wouldn't help because the colorblind individual doesn't have the ability to see that specific color--regardless of whether it is right next to the eye (like contacts) or farther away. So, for example, if there is a person who is completely colorblind and sees everything as shades of gray, wearing blue contacts would not make things appear any bluer--the visual system of the individual isn't capable of perceiving blue.

Also, I suspect that Silver3 may not want her colorblind character to have his/her vision corrected back to normal?


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Corky
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You could have the color that the person can not see take over the whites of their eyes, with the idea being that it stops there and doesn't enter the iris. Some kind of curse, maybe.
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hoptoad
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I am colour blind. Deuteranomalous.
Apparently can't see pale greens and pale purples.

What is funny is that I register as severely colour blind on the isihara charts but when it is investigated further (which had to be done once for a government job ) it was deemed so mild that I would have been granted a pilot's license! So you can register off the charts if they are testing for the wrong type.

About tinted lenses, the brain eventually adapts to counter the imposed colour. Vision will slowly get back to 'normal'.

Its related to colour subtraction. Its like when you place a 50% grey next to a strong colour, the grey will take on the hue of the strong colour's opposite. (IE if you place it next to bright red the grey will take on a greenish appearance--try it, it's cool) This is not the eye seeing a colour that is not there , rather it is the brain perceiving it.

Think of those experiments where people are given spectacles with lenses that invert the light reaching the eye. Everything looks upside down, but eventually the brain corrects for it and everything looks right way up. Then, of course, the scientists take the glasses away and the subject has to put up with everything looking upside down for a while until the brain catches up.

I agree with Survivor on this one, make it have an accompanying trait, even if it is not a dead certain give-away.

Another option is a disease which effects the retina accompanied by visible signs, for instance, eyelids laced with warts where eyelashes should be.

Saw that once ---urgh.

BTW, did you know that severely colour blind people used to be used in aircraft in order to detect camouflaged targets?

2nd BTW All people can experience temporary mild colour blindness by concentrating on bright or illuminated colours and then trying out the colour charts. It is called retinal bleaching and those who test colour-blindness need to compensate for this effect in their subjects.

[This message has been edited by hoptoad (edited January 18, 2006).]


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Silver3
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Uh, no, I don't want his vision corrected back to normal
But I like Survivor's idea, and since my MC comes from an isolated civilization...

Thanks everyone !


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