What follows is the text of a series of messages between myself and a gentleman from China who requested to be identified only as Ranny and that his full name and e-mail address be withheld. I have done some minor formatting to the text to make it easier to read, but have not changed any of the spelling or grammar.

As a note I have removed Ranny's email address out of respect for his privacy

Ranny wrote -

I am really appreciated with your COLOUR BLINDNESS web page, also interested in your conversations with others concerning colour blindness. I am a chinese guy, age-32, male, I am a anomolous trichromat who got weakened red colour sensitivity, or saying, protanously. I can distingush primary colours like pure red, pure green, etc. even pure purple from pure blue. But for mixed colours such as brown-yellow and green, light purple and blue, would be really difficult for me to pick out one from the other. I began to know that I got a colour vision deficiency when I went through a colour vision exam in middle school, that test was Ishara colour dots-pictures. I failed in that test.

When I entered the University I found that there wre a lot of professions restricted to a colour vision defect. Finally I chose civil-engineering rather than architecture which I liked much more. so now I am a civil engineer. There weren't and aren't so many reserches on colour blindness in China, when I faied the Ishara test the doctor simply told me that I am a red-green colour blindness, after that test many friends and family members came to ask me to make differences from objects which coloured red or green, to their suprise, in most cases I got correct answers, and I told them that I know what is red and what is green, but sometimes when the colour becomes faint, I got confused. and other frequent making mistakes are recognizing green which is normally brown-yellow or orange, seeing black which normally very dark red, or taking blue for purple or pink.

I don't meet too many problems in daylly life, so that almost forget my problem, but till now my present job requires me to be able to drive a car from many construction sites, even sometimes working abroad. Someone told me that a man got red-green colour vision deficiency would not be able to get a driver's license, but I am sure that I can make diferences from the three kinds of trafic lights, though the red light seems a little bit dimer, especially from a little far distance. I learn from a friend who recently applied a driver's license that a special screen box is used on testing the colour vison for the license. But I still afraid if I could pass that test, for more I don't want my collegues know that because I got some colour vision abnomal that can not get a driver's license, so far till now they don't know anything about my colour deficiency and I am regarded as very smart and competent in my careeer. My boss now asks me to get a driver's license as soon as possible, but I just afraid to try that damn colour-vision test. If I failed, it means that I shall never be able to drive a car, it's terrible.

From web, I know that nearly 8% of male suffer such colour deficiency, and someone even worse than me as dichromats. I calculated that there should be about 10 million people among US population got somewhat colour vision deficiency, there cannot be so many people restricted to drive cars in USA, wihtout cars how could they go living and working in such a motorized country?. So, please tell me how many from all the anomolous trichromats could pass through the on-driver's license colour vision test and thus get the license in USA? Is there any restriction on driving for a anomolouse trichromat? ( or protanously?) Sorry for my not-accurate English, and looking forward to your reply.

Sicerely yours Ranny, from China

Marty wrote -

It appears that your colorblindness symptoms are very similar to mine. I can see the different traffic lights even when they are in a different order i.e. horizontal rather than vertical, or when there are more than three lights, and there sometimes are in special kinds of intersections. I have never found any problems in driving, other than possibly seeing the little red icons on the dashboard that indicate open doors, brakes on, etc.

I don't know of any restriction in the US or Canada or even Mexico for colorblind people. and I have also driven in the UK with no problems. Most street signs are standardized in terms of shape or design so that isn't a problem. The problem here in the US is that children (and adults) are not routinely tested for colorblindness. Those who enlist in the military are tested (where I was first tested) and for certain color sensitive occupations people might be tested, but it is the exception rather than the rule

You didn't say where in China you lived, but it shouldn't make much difference. What governs are the local DMV (Department of Motor Vehicles) laws. If you don't pass there is no stigma associated with being colorblind, and more than there would be if you were short, or tall, or fat.

The screen box is new to me, but it may just be something to eliminate distractions. If you can see the different light colors and if you can detect the various street warning and information signs you should be alright. As for driving abroad if you have a domestic license you can drive for a short period with no problems and if you stay for an extended period you can get an International license based on our domestic license (as far as I know)

Please let me know how you make out.

Ranny wrote -

I am very glad to have received your reply so quickly about colour blindness, that is really helpful to me. As you described that you've got almost the same symptom on colour blindness with that of mine, while having no problem at all in driving a car. Your driving experience give me much confidence to apply a driver's license. Thank you for your having eased my worry.

By the way, I live in the city of Hefei, Anhui Province, P.R.China. And as to coloured web pages which with coloured characters in coloured back ground, so far I have never found any unreadable, but in real life, I always find some print materials with red in black, or black in red which annoying me to recognize, and some of them are nearly invisible to me. Also I would like to know whether the prevalence ratio of colourblindness to all the human races(whites, blacks or Asians) is approximately the same(saying for male the chance is 8%). Thanks again for your devotion to the colourblind people.

Marty wrote -

Happy to be of help. I have not found any studies of any correlation between race and colorblindness. This does not mean none have been done, it just means that I am unaware of any. The only genetic link know of is that it is found predominantly in males and that it is carried by the female

Please let me know when you get your driver's license

Ranny wrote -

I do consent that you add our conversation to your web-collection, If nobody presented informations to others, there would be nothing on web-pages, I also wish that my colour vision deficiency experience and our conversations would be of help to others who got the similar problem.

Ranny wrote again-

Once again I read your conversation with Dr. Daneis [sic]. About seeing the trafic lights, I have got the same perception with Daneis [sic]. Last night I spent quarter an hour standing at the street cross corner just in watching the different trafic lights to check my colour vision perception, before I possibly go for a driver's license. I found that I can see the green light very well, even from a far distance. It's very clear green light. But if the yellow light has the same intensity with the red one, I may not be so prompt to tell the red from the yellow, and the red light is really the dimmest of the three. No matter in day light or at night I always find the green light the most noticable and can't imagine how could it be looked as white or as street lights, on the contrary, because my red sensitivity is not strong enough that the red light appears not so noticable, that if the intensity is not strong enough that I would ignorn it.

Ranny sent this update -

First, I was asked to look into an instrument somewhat like a microscope, in which I could see a coloured light disc about 1 CM of diameter, the upper-sphere and downward-sphere of the disc changing in different colours by adjusting a tune wheel of the machine, the colour changing along the light wave length from red to yellow to green, now beginning with the upper and down in random different colours, the examer asked me to adjust the tune to make the whole sphere of the disc right in the same red, same yellow or same green, additionally on the equater of the disc there was always a very thin coloured line, eg. on yellow disc it may be red or green , on green may be yellow or red, and even the colour of this line also should be detected and answered by the applicant.

Secondly I went to an other room siting before a black board, on which there were three small indicator lights, respectively in blue, yellow and red, on the desk where I sat by there were correspondingly three buttons each for the above lights, now the examer swiched on different lights in random very quickly and asked me to press the corespondent button in same quick response, in this test the colours of the lights were very easy to recognize, I think they mostly wants to check the applicant's respond reflect.

Now may I ask you what kind of colour vision test is used for a driver's license in your home town, or your country, I am interested in knowing how it was like when you got your colour vision tested for your first driver's license, was it easy for you, or simply there were no colour vision test? And is that possible for a real dichromat to drive a car? should a dichromat possiblly recognize the different trafic lights? For me if far away from the lights and the green one happened to be in low intensity , it might be difficult for me to recognize between the green one and the red. Hope to see your reply!

Marty wrote -

I was very interested in your latest message.

The test they gave you was very comprehensive. Much more so than any test I have taken here in the US.

It has been almost 35 years since I was given my pre-military (Air Force) enlistment colorblindness test and they only used the Ishara charts. I took my one and only driver's license test more than 40 years ago and if memory serves me the test consisted of a written test (Motor vehicle and traffic laws, traffic light and sign identification, etc.) They gave no formal colorblindness test that I remember. The major part of the test is the street driving test. I guess they assume that if you can stop at the red lights, go at the green lights and response to the colored signs (which also have distinctive shapes) you are fit to drive. The tests may have changed in the intervening period but I can't verify that.

At my most recent eye exam given by an Ophthalmologist (MD) the only colorblindness exam test he used was the Ishara charts. I should also add that he administered the test at my request, not as part of the normal eye exam.

I wonder at the reasons why they administer such a comprehensive test to you. I has assumed traffic lights and traffic signs were pretty standard all over the world. That means signs can be identified by shape and design (usually icons) and traffic lights are of a standard color and intensity. As far as I know, If you have a valid driver's license in one country you can pretty much drive in any other

I am happy to hear that you passed your test and I assume that means you now have a good shot at getting your driver's license. Now all you have to worry about are those other drivers who have licenses and who may or may not observe the lights and signs that we now know they all can see.