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Color Vision and Point of Care Testing

Published July 22, 2011 6:03 AM by Scott Warner

An early physical exam included a test for color blindness. I was shown a book of dotted pictures with numbers “hidden” inside them (sometimes called Ishihara diagrams). If I could see all the numbers, my color vision was fine. If not, I would have to find a different profession. Color vision, I was told, is essential to performing lab testing.

Color blindness is caused by a defect in retinal cone cells that affect how they absorb light. Cones sense red, green, or blue light, so these are the colors affected in variations and degrees. Since many test interpretations rely on color indicators, it makes sense that laboratory workers would need to see them accurately.

I’ve no idea if current programs require a color blind test, since there are few manual methods left. But these few are important: urine dipsticks, bacterial colony assessment, Gram stain, etc. Our procedures often reinforce the importance of accurate color vision. I can imagine most lab techs take it for granted.

But what about doctors and nurses performing point of care testing? Are any color blind?

Possibly. Color blindness affects more males (7%) than females (0.5%), because it is usually a sex-linked inherited disorder. In female-dominated professions such as nursing, this wouldn’t seem to be a significant issue. But there are plenty of males, just the same.

I had never considered the issue until a nurse asked, “Do you need nurses performing lab tests to be tested for color blindness?” Asking it tells me that nursing may not require testing. And if we want to start, how do we find out and what do we do with the information? Competency assessment won’t discern all variations. As straightforward as Ishihara diagrams seem -- there are online tests -- the cause isn’t always genetic. I’m not qualified to diagnose, that’s for sure.

Who gets tested, when, and what do we do with the results? Will a hospital add it to preemployment physicals if only the laboratory requires it? The issue has shades of gray. Let me know if you have run across this problem.



Thanks for sharing.  It seems like a good idea, especially if it can detect other problems.  Fascinating!

Scott Warner July 27, 2011 6:19 AM

At every location that I have developed or administered a POCT program, I have institutes web-based HealthStream color blindness screening.  While the lab may not have many manual methods, POCT is heavily weighted on them.  It is common knowledge that POCT can be difficult to manage, let alone without knowing if there is a potential failure point.  For CAP labs, this is a non-negotiable requirement for all who perform testing.  Interestingly enough, depending on the state requirements, many other hospital professionals are also required to be routinely screened, so developing a system wide screening is widely beneficial.  These can include radiology techs, bio-med/maintenance, and security.

In my programs, we schedule the screening to occur initially and annually thereafter.  While it is true that those with the genetic abnormality will not change, brain tumors and eye diseases can develop rapidly and go undetected for more than a year.  In one of my programs serving over 4,000 POCT operators, 2 nurses failed on an annual screening.  When they were seen by employee health, both failed and were referred out to their providers.  One was a brain tumor and the other fast developing cataracts.  Neither had any indicators as the changes were gradual enough that they did not realize they were occurring.  The nurse with cataracts later told me that during that year she had painted her kitchen what she though was a robin’s egg blue and after corrective surgery she understood why her family protested so loudly – it was a very bright turquoise.  So it is not only a safety step but a free employee benefit.  

Ginger Baker July 25, 2011 2:43 PM

Great article & good point.  I hope that you will get more dialogue going about this topic for my information & future reference.

Monica Newby July 22, 2011 7:48 AM

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About this Blog

    Scott Warner, MLT(ASCP)
    Occupation: Laboratory Manager
    Setting: Critical Access Hospital
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