Colour vision test

[Canopus]

Has your kid ever had a colour vision test?

[Flora]

canopus do you mean for colour blindness? Or the work that Ian Jordan is doing with coloured lenses?

 

Either way, yes to both.

 

Lauren

[Canopus]

As in a test for colour blindness.

[Zemanski]

Yes, it's one of the few visual problems Com doesn't have.

 

Z

[Suze]

yes my son has had a test..........no he,s not colour blind.

[Canopus]

Which test was used? There are several colour vision tests available including Ishihara, Farnsworth, City University, and lantern.

[Zemanski]

No idea

 

Z

[darky]

yes, my son has had one, and again, is one of the vision problems he does not have. (colour blindness)

[Ian Jordan]

It would be unusual to use anything other than an ishihara or city test on children, lantern tests tend towards specific occupations e.g. sailor, the farnsworth is very unusual test in practice. There is limited benefit in complex testing except in very specific cases - usually only if a job is dependent or pathology suspected.

[Canopus]

I think the conventional Ishihara test is inappropriate for schools. It is very high standard test and works more as a pass fail test rather than indentifies the degree of colour discrimination deficiency. When a kid fails an Ishihara test they are told the devastating news that they can't become an airline pilot, train driver, or even an electrician. There are better tests available than the conventional Ishihara test that more clearly identify the degree of colour discrimination deficiency and are more suitable for use with kids.

 

I am slightly protanopic (red desensitive) and failed a conventional Ishihara test at school. I have passed a modified Ishihara test and a lantern test.

[Ian Jordan]

They are often administered incorrectly too.

But unlikely to change in the forseeable future

Accurate colour testing is relatively expensive with limited benefits in high levels of accuracy.

For the majority as it is rare to treat symptoms and jobs usually will reject any candidates who have treatment to mask symptoms. For the few that fail screening (4 - 8% are colour anomalous to some extent) if it impinges significantly on their life then of course other tests are indicated. But this is a relatively rare occurance.

Edited May 7, 2006 by Ian Jordan

[Canopus]

For the majority as it is rare to treat symptoms and jobs usually will reject any candidates who have treatment to mask symptoms.

 

Does that also apply to the tinted lenses for AS, ASD, and dyslexia? I doubt anyone would allow tinted lenses to be used for a colour vision test or as a treatment for neurological conditions in the workplace. What should a user of tinted lenses for AS tell an employer when he comments on them in a job interview? I was told at school that it was downright rude to go into a job interview with any tinted lenses.

[Zemanski]

surely it is downright discrimination to ask a person with a condition like prosopagnosia to enter an interview situation without their tinted lenses if they give them a chance to process facial input on more of a par with other people?

 

There is nothing rude in a person with short sight wearing glasses or a blind person carrying a cane, I can understand the idea that wearing them for cosmetic purposes would be inappropriate but certainly not for the purposes of alleviating the difficulties caused by a disability.

 

I would think that I would probably encourage Com to refer to his need for lenses alongside informing a potential employer of his AS - that way they will be expecting him to wear lenses and know why.

[Ian Jordan]

Some jobs have specific exclusions for safety reasons on colour vision problems eg pilots, train drivers, deck officers on ships, electricians - and I for one would prefer it stays that way as metamerism could cause major problems in some circumstances. A colour blind pilot could be lethal.

As for any other restrictions I have never heard of any instance in which tinted specs restrict jobs and it would not be acceptable for any employer to discriminate. A painter and decorator may find it difficult with tints but common sense comes into it.

But it is probably best to explain - most people are reasonable

[Canopus]

surely it is downright discrimination to ask a person with a condition like prosopagnosia to enter an interview situation without their tinted lenses if they give them a chance to process facial input on more of a par with other people?

 

Most employers and interviewers have never heard of prosopagnosia and if they are given an explanation during the interview they will probably laugh their head off and think the job applicant is a complete nutcase.

[Canopus]

Some jobs have specific exclusions for safety reasons on colour vision problems eg pilots, train drivers, deck officers on ships, electricians - and I for one would prefer it stays that way as metamerism could cause major problems in some circumstances.

 

Are you actually saying that anybody who want such careers must score 100% on an Ishihara test?

 

A colour blind pilot could be lethal.

 

There are people in the aviation industry that challenge the colour vision testing policy. They claim the Ishihara test is unrealistic for an airline pilot and better suited for people who restore antique paintings. Warning lights used in aviation are designed to be saturated and monochromatic whereas the Ishihara test uses desaturated colours.

[Zemanski]

Most employers and interviewers have never heard of prosopagnosia and if they are given an explanation during the interview they will probably laugh their head off and think the job applicant is a complete nutcase.

 

Then they could well find themselves in serious trouble, and I would be advising Com to tell them at the application stage not at the interview which would put it in writing anyway and give potential employers time to research it.

 

Com is not going to get a job by trying to hide his disabilities because the moment he walks into an interview they will be obvious and he will have been patently dishonest in his application. However he informs employers it will be to his disadvantage where they are prejudiced, at least if he is up-front in his applications he will hopefully have a chance with those who are unprejudiced and appreciate honesty.

 

Zemanski

[Ian Jordan]

Ishihara is just a basic test - aviation needs different methods - as do naval and other jobs, colour vision in aviation does not just look at lights - dichroic filters are used in landing and there may be other colour coding techniques - but you are right i- very saturated lights are less likely to be mistaken. There are also a number of effects that are not often recognised in colour deficiency - peripheral field effects, attentional fields, energy levels to stimulate response etc.I still would consider pilots need optimum performance and would definitely prefer optimum colour vision.

[madmooch]

H has had no tests at all for anything ( except fragile X, which he doesn't have)

 

Grrrrrrrrrr, Sorry, I'm not happy at all at the mo with the school, LEA ,everyone

[Canopus]

Has there been any research into whether people with AS perform worse on Ishihara tests than NT people? There is a possibility that the dot patterns can badly confuse some people, especially if there are also dots without a red or green component such as grey, black, or yellow found on some Ishihara plates.

 

Passing an Ishihara test is a two stage process: Firstly being able to distinguish between colours with a red and green component which is a task of the eyes, secondly being able to piece together the pattern to form a number which is the task of the brain. I can identify regions in an Ishihara plate that are a different colour in a short glance and tell whether it is a 1 or 2 figure number but have difficulty working out the number unless I stare at the plate for some time. Obviously this shows that my eyes can discriminate between colours but have difficulty in pattern recognition.

 

There I some Ishihara plates with dot patterns that drive me mad just looking at them. They are not always the ones I have most difficulty identifying the numbers.

[Canopus]

Ishihara is just a basic test - aviation needs different methods - as do naval and other jobs, colour vision in aviation does not just look at lights - dichroic filters are used in landing and there may be other colour coding techniques - but you are right i- very saturated lights are less likely to be mistaken. There are also a number of effects that are not often recognised in colour deficiency - peripheral field effects, attentional fields, energy levels to stimulate response etc.

 

Are implying that the Ishihara test is overrated? It is generally regarded as the gold standard of colour vision testing but very few people seem to know how it works. It is often administered by teachers and employers who know very little about colour perception.

 

I still would consider pilots need optimum performance and would definitely prefer optimum colour vision.

 

So what would be the most appropriate colour vision test for a pilot?

[Ian Jordan]

Ishihara test is not gold standard test - there are number of very good tests e.g. Nagel anomaloscope.

It is however a good screening test (properly administered) but metamerism is important and it is more often than not incorrectly applied. (even by optical professionals). It is designed for daylight use and the results are different in artificial lighting.

Pilots will use lantern test, there are more than 1 type of lantern test though - seaman use a different type.

Colour vision is not however static and is not a constant measurement.

 

The methods we use experimentally work in 3D colour space - and are very interesting as they can provide a quantifiability of colour.

 

But highly accurate testing is usually not done - the benefits are limited.

[Canopus]

Ishihara test is not gold standard test - there are number of very good tests e.g. Nagel anomaloscope.

 

Most employers still regard the Ishihara test as a gold standard test and use it to screen job applicants for positions requiring a high degree of colour discrimination. If the applicant performs poorly on the test - often conducted under inappropriate lighting conditions - then they will usually be rejected.

 

It is however a good screening test (properly administered) but metamerism is important and it is more often than not incorrectly applied. (even by optical professionals). It is designed for daylight use and the results are different in artificial lighting.

 

I know about this one and see Ishihara plates differently under different light sources. My optician regularly performs Ishihara tests under incandecent lights and I have told her that the test is only valid under daylight conditions but it still hasn't sunk in.

 

Pilots will use lantern test, there are more than 1 type of lantern test though - seaman use a different type.

 

Pilots still have to pass an Ishihara test in the UK. I have read that lantern tests are an acceptable alternative in the US and Australia.

[Ian Jordan]

CAA pilot standards

 

If screening is OK with Ishihara then no need for lantern test

 

The CAA uses three classificationsfor colour vision: CP2 (normal), CP3(safe) and CP4 (unsafe). Colour visionassessment is carried out with theIshihara plates (24 plate version tested indaylight or artificial light of the samecolour temperature). For CP2classification, the patient must make noerrors. A patient who fails the Ishiharatest is then assessed with the Holmes-Wright lantern, which must be passed forthe colour vision to be classed as safe(CP3).The Holmes-Wright lantern consistsof two lights in a vertical plane, whichthe subject must name correctly at adistance of 6m in a normally lit room.Although each colour will have differenthues on different presentations, thesubject must identify both lights on eachpresentation of red, green or white.There are nine presentations on eachrun and if the subject names all lightscorrectly, then no further runs need to beused; presentations are made in differentorders to prevent learning.

[Canopus]

Something I have always wanted to know about the Ishihara test are:

 

1. Why are numbers used? The original Ishihara test used Japanese symbols and Ishihara like tests with shapes exist but they are rarely used in practice.

 

2. Is there a reason for including spots without a red or green component such as black and yellow into some test plates?

 

You are right about pilots only needing to pass a Holmes-Wright lantern test rather than an Ishihara test, but do opticians generally know this?

[Ian Jordan]

I assume numbers are easy to describe but there may be another reason. I doubt whether confusion would even have been considered

 

other colour tests other than red green are incorporated into ishihara test

 

The optical professions should know about colour vision testing - they won't remember all standards (there are a lot of them) but it easy to look them up. But colour (and colour vision problems) are usually not given a high priority - done properly they are costly in time and not remunerated. There is little incentive and time is usually short in a practice situation. Few practices would have anything other than a basic test.

Edited May 13, 2006 by Ian Jordan