Hi all,
I totally flunked the Ishihara plates (8 fails / 15) and my AME slapped a VCL restriction on me. She referred me to Heathrow Medical for a further CAD assessment if I wanted to pursue the issue further, but advised that only a small portion of people actually pass that.
The CAD assessment itself (the diagonally moving colour block) was hard and I felt I was guessing more than a reasonable amount to be able to pass so I was fairly resigned at that point.
However I'm very pleased to report that I'm only mildly protan deficient and able to pursue a full unrestricted class EASA 1 & 2.
So my contribution is, if you find yourself failing the Ishihara plates it is by no means the end of your story. Get a proper assessment at Heathrow Medical done and you may surprise yourself.