Online colour vision test
I found this online colour vision test and it is basically an online version of the Farnsworth Munsell 100 Hue test. It involves moving little discs of colour around until you get a smooth transition from one colour to the next. What could be simpler? Well, I stared at the 3rd line in this online test and hardly moved anything – they all looked the same!
Here is how I scored:
I scored 146 and that seems to place me a long way to the right of the scale. The results page telling me which colours I am poor at discriminating is less useful given that I am not 100% sure of the colours in the areas that are the worse! It looks like orangey-reds and pinky-purples seem to be bad but I could be wrong…
There is always some concern with doing these tests online as monitors can play havoc with colours. It might be interesting to sit down with someone who had normal colour vision and do it. My degree of colour vision deficiency has never been quantified. I’ve only ever had the Ishihara test (commonly found lurking dustily on GPs’ shelves) and I’m off to the City University London Colour Vision Clinic in a couple of weeks to get formally assessed.
Colour blindness and cricket
One of Australia's best ever batsmen (and, er, colour-blind)
This was originally posted at http://northerndoctor.com in May 2009.
Economic collapse. Mendacious MPs. Revalidation. Litiginous chiropractors. I’m feeling oppressed and I feel I need a tonic. And what better a tonic is there, in early summer in England, than cricket?
I would have liked to have settled down to enjoy some cricket today but sadly the swingeing cuts seem to have also impacted upon Test cricket and we have been reduced to a 3 day game.
So I have been musing on my own personal cricketing failings. I have always suspected that I am handicapped by my colour-blindness. Think about it. How do you fancy spotting a red ball on a green background with an inability to tell red and green apart? It turns out the medical literature has already considered the issue and is there to back up my plaintive pleas.
There is an expected prevalence of around 8% in the male population for colour-vision deficiency. Of course, an incidence of 8-9% means there is likely to be one colour-blind player in every team. Previous studies quoted have suggested rates as low as 4% in first class county cricketers. This study looked at 293 cricketers from seven cricket clubs in Melbourne. They found that 8.9% had colour-vision deficiencies but only 6.7% played at the highest level within those clubs. However, that reduction in those playing at the highest level is statistically significant.
This could lead one to the conclusion that colour-blindness is holding some cricketing men back. This study also looked at some other interesting areas which might prove useful for the village cricket bluffer and will provide ample ammunition to mount a robust defence of any mishaps.
The batting average in those with mild colour-vision deficiencies was 28.3 and those with severe deficiencies was 18.8. (Sadly, the authors report this was not statistically significant but don’t let that stand in the way of your bar-room thesis during the match post-mortem.) It was also noted that those with colour-vision deficiencies rather prefer fielding close to the batter. This might prove a highly useful piece of hard medical evidence for those that find galloping around a boundary rope somewhat wearing. The authors have included some technical explanations which will help beat back any naysayers.
A further hypothesis is that cricketers with abnormal colour vision will have greatest difficulty when fielding in the outfield where the angular size of the ball is small and the ball may often be seen against grass or surrounding foliage. The ball subtends about 12 minutes of arc for a fielder close to the batsman and three to five minutes of arc for a fielder near the boundary. It is known that all observers with abnormal colour vision, even those with a mild deficiency, have difficulty seeing red objects in natural surrounds. For these reasons cricketers with abnormal colour vision should prefer to field close to the batsman.
Rather amazingly 42% of men in this study did not know they had any colour-vision deficiency. So the next time you shell a dolly at long-off perhaps you ought to toddle down to your GP and do an Ishihara test. It could provide some convenient excuses.
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Harris, R., & Cole, B. (2007). Abnormal colour vision is a handicap to playing cricket but not an insurmountable one Clinical and Experimental Optometry, 90 (6), 451-456 DOI: 10.1111/j.1444-0938.2006.00180.x
This was originally posted at http://northerndoctor.com in June 2010.
I am red-green colour blind and I’m well aware of my general inability to distinguish red particularly well. In particular, I often miss subtler shades of pink. Apart from a tendency to wear inappropriate shirt and tie combinations it’s hardly life threatening. However, it is perhaps rather more than an inconvenience that blood is red. People that are colour-blind may be unable to spot early signs of blood loss. And as any fule kno unexpected blood rings big fat alarm bells for the Big C.
A good example is blood in the urine. I doubt I would miss frank gross haematuria but a red-green colour deficiency makes it easy to miss an elegant pink tinge in my urine. This simple study from some urologists in Preston took 200 male patients with bladder cancer and assessed them for colour deficiency using an Ishihara plate test. They found 21 gents (10.5%) had red-green or ‘complete colour blindness’. The presentation at diagnosis was frank haematuria in 74% of the non-colour blind versus 62% of the colour blind (non-significant).
The study also looked at the histology and the non-colour blind had 69% with superficial disease and the rest had invasive bladder cancer. The colour-blind group had 42% with superficial disease and 58% with less favourable histology. This is statistically significant (p<0.01).
There is sound logic to back up these findings. Colour-blind men can’t pick up some of the early signs of disease when it involves spotting colour changes in bodily fluids. So they are presenting later with more advanced disease. Not good. However, this is a small study – only having 21 cases of bladder cancer in colour-blind men limits how far I would want to rely on the findings.
Colour-blindness is treated as nothing more than an evolutionary oddity; good for teaching the basics of X-linked inheritance but of no clinical significance. If you are a clinician when was the last time you asked someone if they were colour-blind before asking about blood in the urine or faeces? I’m guessing most GPs don’t give it a second thought.
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Katmawi-Sabbagh, S., Haq, A., Jain, S., Subhas, G., & Turnham, H. (2009). Impact of Colour Blindness on Recognition of Haematuria in Bladder Cancer Patients Urologia Internationalis, 83 (3), 289-290 DOI: 10.1159/000241669
