Morning all!
Well, here is my account of the colour vision assesment that I took at City. I chose City simply because at £125 +VAT for various tests it seemed like I would get a better understanding of my CVD that I would if I paid Gatwick £130 just for a pass fail on the CAD.
Got to City and was taken into a small lab type room where I did the following tests. For all of these the room was darkened and the tests were illuminated by what appeared to be a daylight type bulb (unsure of the exact name).
Started of with the Ishihara plates, most of which I couldn't make out. What I would say at this point is that while many people say lots about how you can't practice these on a computer as the lighting and colours will be all different etc etc, I would say this is probably only relevant to people with very very slight CVD (which it turns out mine isn't but we'll come to that in a bit!)
Next up was a test similar to the IP's but with symbols, triangle circle square etc pretty straight forward. Can't really guage how I did in this yet as my full results are being sent out to me in the post.
Next up was a test involving looking at a book with 5 small (about 6 or 7mm across) coloured dots on each page (black backgroud) with one dot in the middle and the other four layed out to the top bottom left and right. I had to choose the dot closest in colour to the centre. The important word here is colour, not shade or brightness. For example the centre spot might have been green, with a brown a red a green and a purple for effect as the coloured dots around it. Obviously the green one would be the right option, but those with green CVD will know that identifying the green one isn't easy, so you tend to go for the one that looks closest in shade instead, which invariably turns out to be the brown or the red! lol
Next up was the D-15, standard 'here's 15 coloured discs, arange them in order so that the next one is closest in colour to the previous.
Then came the moment we've all been waiting to hear about. The legendary CAD test. Now before I go into it let me just explain that I in actual fact did the CAD test twice yesterday. Not because I was close to a pass but because the standard City CAD test differs slightly from the CAA CAD Test. I'll go into these in a sec.
So the City CAD test comprised of sitting on a stool with my chin resting on a support looking at a screen that was about a meter and a half away that had the familiar CAD square in the middle of it, however it was quite small, very small in fact, I would say that the whold grid was no more than 2 inches at most, which viewed from a meter and a half starts to shrink rapidly! The remote I had only had four buttons on it and was connected via a cable direct to the back of an old DOS based PC. And away we went. As has been already posted here somewhere back among the million other pages, you see (or don't in my case) a coloured square moving its way across the diagonals of the grey, almost white noise like, backgroud. The box moves to one of the corners and then you have to identify which corner the box moved to by pressing the corresponding button on the remote. The test only shows you one box at a time and doesn't move onto the next one until you have pressed a button on the keypad. So you can take a break at any time simply by remembering which button you have to press next but not pressing it until you are ready to start again. A lot has been said on here regarding being able to guess the right answer if you don't know, while I agree that its true, your chances of getting it right are one in 4, I must have pressed that button at least 15 times in a minute and been sat there for at least 8 minutes, thats 120 times, at least. A good portion of those were guesses, I would estimate over 50% so at least 60 were a guess...... now I'm no mathmatician but the chances of getting 60 complete guesses right are, I suspect, quite large.
The lady conducting the test explained that it was normal that there would be some I couldn't see as they neeed to find the threshold at which my CVD hits. It's difficult to offer any advice for how to approach the CAD as everyone will be different, but I found it easier to starte at the little white dot in the middle and let the 'grey noise' almost become a blur, as opposed to trying to locate the coloured square as it flies accross the box(it moves quite quickly!).
Once I was done with this, the lady said that as I'd expressed an interest in aviation that I could also sit the CAD they use at Gatwick if I wished. An interesting comparison I though so why not! Off to another room where there was a similar setup with a few small differences. Firstly the computer connected was a shiny laptop running Windows not DOS. Secondly the remote used to control the test was indeed a wireless device (essentially a bluetooth numeric keypad with some red plastic buttons glues to the 1,3,7 and 9 keys). Thirdly, the monitor on which the test was done was a nice Flat screen monitor, adn fourthly the test grid itself was substantilly bigger on the screen, I would say a good 4 or 5 inches across. I did 2 seperate runs on this version, one to look at my blue yellow vision and the other for the red green. The test worked in the same way, in that if you press a button on the control it moves on to the next one (meaning that if there were a problem with the control, or that the button presses weren't being recognised by the laptop the test itself would just sit there and not move on).
Results for this one were given to me straight after. Turns out my Blue Yellow vision is in fact better than normal with a value of 0.8 (1 being normal, lower being better and higher being worse), however my red green (green inparticular) vision was a country mile away from being good. I scored a whoping 22 and a bit on that one, meaning my green colour vision is 22 times worse than most people. 'Surely you should have known it was that bad before you went you fool!' I hear you cry. Problem is (and other CVD people may or may not agree with this) that knwoign you have CVD and knowing how bad it is are 2 completely different things. because someone with CVD will never see what you are supposed to see there is nothing to compare it against and so while you may know there is an issue there is littel way of knowing how bad it is, until that is, you take a test like the CAD which can put a value on it.
Anyways, I feel better now at least knowing that i'm not borderline and that I can look into other things. I now have a couple of options:-
1:- Lobbying to have all the aviation red green colours changed to a blue yellow system so I can see them and pass tests without issue (anyone up for writting a few thousand letters with me? LOL)
2:- Exploring the possibility of becoming an Aircraft Engineer of some sort (I have an IT background, not sure if its any help though), anyone have any advice on this one?
Any questions feel free to ask!
ChiefDM