Collective Colour Vision Thread 4

[sethgecko]

This thread was incredibly helpful to me so I wanted to share my experiences with colour vision testing.

When I was 16 I had an Ishihara plate test in which I struggled with a few and made some errors. The examiner at the time (I think it was just an opticians, so long ago I cannot recall) advised that I would never be able to become a pilot. I do remember asking if I was colour blind and his response was that I had a colour deficiency but it was so minor he could not put a number to it. A someone cryptic response but as a young 16 year old lad, dream dead, killed off right there and then.

When I became interested in seriously pursuing an Aviation Career I was concerned that I would not meet the colour vision requirements. I found some of the Ishihara tests online and had mixed results, one of them I completed with only 2 errors and the other I complete with zero errors. I also stumbled across the CAD test and history of how this was developed, perhaps there was some hope for me yet.

So fast forward to February this year and I attended Heathrow medical services for my initial Class 1. I saw the Chief Optometrist, Dr Adrian Chorley who was a thoroughly professional and general great guy, he made me feel at eases as he explained the various testing procedures. We came to the Ishihara plate test, a book on a stand presented below a lamp. I recall that this test had to be conducted under specific lighting conditions and clearly this was catered for here. The Optometrist began to turn the pages, the plates looked very different to what I had seen online, lots of purple colours. I really struggled and knew I had made errors. We completed some other testing then we discussed the Ishihara plate test and that I had scored 6/15. The Optometrist mentioned that there was another test we could do, I asked if this was the CAD test and he confirmed.

I was seated in front of the machine and the test was explained to me. There are lots of grey boxes on the screen, it kind of looks like pixelated graphics from 80's computer games. There will be a coloured boxed that travels across the grey boxes in a straight line (out to one of four corners). You have to click a button to confirm the direction it went in. You could compare this to the audio tests in the way that the sounds get fainter and fainter, the same happens with the colours. The optometrist also advised that the test would identify my weak areas and test them more rigorously. Sure enough the clear coloured boxes became fainter and fainter. If you see no colour at all you just make a guess, the next colour box will not start its journey until you press a button. I found this test challenging as it lasted quite some time and at times the boxes were so faint I had to make some guesses. As the test progressed and the guesses increased my heart started to sink, I was very worried that I was failing this.

We got to the end of the test and I braced myself for the results. The optometrist advised that I had a colour deficiency and took time to walk me through the results. The good news is that I had passed the test. He provided a print out which shows the threshold and your results. My diagnosis was that I had deutan deficiency and normal YB colour vision.

R-G threshold 2.92
Y-B threshold 1.54

This put my colour test result into the following category :

Mild Deutan / Proton deficiency threshold <6 deutan, < 12 protan which enables a a fit unrestricted EASA Class 1 and 2. Unfit European Class 3, Fit UK Class 1.

I hope that my contribution is of some help to others as I read this thread in its entirety before my medical and it was very helpful.