Understanding the Colour Blind Test - Including Self Red / Green Colour Deficiency Test - Dr Gill

[Music] [Music] hello ladies and gentlemen and welcome back to my channel my name is Dr James Gil and you join me here today to look at the ishihara charts and a little bit of color vision um the isihara chart is used to determine if someone has a problem with their color vision or is color blind as this is often termed now the ishihara chart is a color deficiency test not a color blind test and I think that's a very important thing for us to highlight here um it's the most common test for uh looking at color deficiency but there are other tests available broadly these are going to be um you know things that are used to diagnose specific forms of color vision much beyond the red green color blindness um and for the vast majority of medical students and Junior doctors having a working understanding of the isihara chart should be sufficient um let's put it this way if the ishihara chart isn't giving the answer then you need to get further help so to be clear the isihara chart is designed to look at congenital dist disturbances of color vision and that's probably a good place to highlight how common color vision is in chaps you're looking about one in 12 people affected whereas in women because it's an excellent genetic condition I women have a backup it's much rarer there we're looking about one in 200 so with that in mind before we go on to look at how to use the isihara charts I thought it might be a good idea to look at what color blindness actually is so normal colision is termed TR chromatism I.E you're able to see the red green and blue um in their true forms away from trir chromatism the majority of color vision deficiencies are actually red green color blind there is a yellow blue deficiency but that is very rare and certainly not something we need to discuss today now there are two types of color division broadly you have a protan deficiency and a dutan deficiency those are subdivided into two further categories the protan deficiency is split into protanopia and protanomaly essentially we're looking at a total and a partial deficiency there and kind of makes sense there for that we'll see the dutan deficiency further split into a total and partial deficiencies this time referred to as dutan Opia or deutrom Malia so what you really need to remember is that a protan deficiency affects sensitivity to red light and a dutan deficiency affects sensitivity to green light in terms of the subdivisions when I say that protanopia and dutron Opia are total deficiencies red or green I mean in the absolute sense these people cannot perceive red nor green respectively by contrast protanomaly and deutrom Mal are more subtle you've got degrees of an inability to perceive red or green essentially it's a case of non versus some so with protanopia these people have an absolute uh lack of red cones thus they cannot perceive red or more likely perceive it as black whereas protano Mali these people have some uh red cones but they can become um confused with colors so they will often find Browns and dark greens similar dark orange and dark red can be confused and again some mid greens will be confused with oranges and we certainly going to lose a subtlety and um a contrast to those colors dut tropia is the absolute loss of green cones and thus the loss of green color and when we have the milder forms deutrom Malia that's going to mean mid Reds and mid greens will look the same because of this we can also have bright greens and bright yellows look the same pinks and light Grays can look the same along with mid Reds and mid greens now I highlight this Doral because this is my color blindness to give you an example I can't see hollyberries on a holly bush until I get up close to them similarly uh whilst preparing this video I noticed that there is a plant pot in my office it is gray as far as I'm concerned but apparently Beth said it's pink similarly I have a really nice uh bright yellow lumos helmet that goes with my bright yellow cycling jacket and I'm reliably informed that my helmet is actually green but they look the same to me so I've been very clear so far with this video um that I've been cautious with my words so saying that gray and pink can be perceived as the same and that light green and light gray can be mistaken for the same okay that's because we need to go back to the fundamental facts of how Vision work and light for that matter Works let's just recap that now a red apple is only red because the M the the the tissue of the Apple absorbs all other light other than red and that red is reflected back so the red light is reflected off the apple and thus we perceive the apple as red because it's the only thing coming to us in a similar way a red light is either a white light with a red filter on it so only allowing red light to come out or we're getting light from a source that will only imit a red light such as burning strontium or calcium there we go I never thought my gcsc chemistry would come in useful but what do you know um so this is why I've taken care to use the words appearance and perception when dealing with cision let's just quickly touch on the physics there visible red light is in the electromagnetic spectrum for 700 nanometers we've kept gcsc chemistry happy we may as well keep gcsc physics happy too um so this is an electromagnetic input um that our eyes will perceive and stimulate the uh the cones on the retina and there we'll get a chemical response to that light this chemical response a neurotrans mitter is converted into an electrical signal and passed through the optic nerves to the occipital lobe at the back of the brain and here we perceive that electrical stimulation as vision and color so once again we've returned to that scenario that we as humans as mammals are actually brains sitting sealed within a black box vividly hallucinating the world around us based upon electrical stimuli that is coming into us we will never see a color or a light for that matter what we will do is we will perceive the effect of that light when it hits our retina so to drop a matrix quo in at this point what's really going to bake your noodle later on is is your color vision the same as my color vision well any of you who've seen my cranial nerve videos will know that I've touched on the isihara charts before and I seem to have got them wrong well that's because my perception of color vision is a little bit broken so quite possibly I don't see the world the same way that you do now I think that's enough of an introduction to color deficiency but before we go into looking at my possibly your color vision deficiencies I just want to ask something of yourselves if you'd like me to deal more into color deficiency the genetics the problem with the retina the rods and cones and things drop us a comment down below and we'll see about doing a video to look into what causes color defici color vision deficiencies in a little bit more detail so with that in mind let's go back to our ishihara chart plates that we started off the video with it's important as far as the ishihara plates are observed that we do it correctly ideally we want to be having them observed by daylight so by window or realistically as in most clinics a natural light mimic a light that's too cold or too warm can cause color deficiencies uh that aren't true I mean we all know what it's like when we've got our phone on night mode we've got the warm background and everything's got a slightly orange Hue that will be the same as looking at the ishihara charts with a too warm or twoo orange bas light when our phone is in night mode the colors don't look right and similarly the ishihara charts wouldn't look right under that light either so make sure where possible we're using a natural light also we need to have the charts 75 cm away from the patient and held up across their field of vision not placed flat on the table with that in mind we're going to progress to the very first place plate now this plate should clearly have the number 12 on it this isn't a test of color vision as you can see we're looking at sort of Grays and oranges um what we are doing here is testing the patient's Vision if they can't see the 12 at this point then there's no uh benefit in continuing on with the rest of the ishihara test what it does also do is highlight to people how they will perceive the shapes or the numbers in the test made up of the different dots and colors going forwards when we use the ishihara chart plates we want to try and minimize the exposure the patient has to them so we're going to give them the plates for 3 seconds and ask them to answer as quickly as they could now medicine isn't black or white you'll have to pardon the pun here and thus we're going to score um a patient on these charts it's not pass or fail what we will find is someone who scores over 17 is considered to have normal color vision while someone who scores under 13 has a color deficiency that we'll be able to clarify later on but why what happened to scores of 14 and 16 I hear you cry well there are some people who have very rare color deficiencies that will be able to score between 14 and 16 but that's not something that can be diagnosed further with the scope of the ishihara chart would certainly need more in-depth investigations and we're not going to be able to look at that here so with that in mind under 13 uh is going to indicate a um a color deficiency honestly I think it's easier to show how the plates work rather than tell you so with that in mind let's uh get pen and paper or just anything to write with and I want you to draw three columns please so with our little demo here I'm going to show you again the first plate if you can't see that then I really think you should talk to your optician on the bit of paper that you've got I need you to score um plates 2 to9 in one column we're going to score 10 to 17 in the next column and 18 to 21 in the third column so let's have a look over those plates now please uh write down the numbers as you perceive them as we go along and then we'll top them all up at the end so for column one everybody should be seeing uh number 12 on plate one plates two and three plates four and five plates six and seven plates eight and nine so that should complete uh the plates for column one okay so let's go through the answers in inverted commer to those plates so we all know that plate number one was our control so we've all seen 12 there on plate two if you had normal vision you should have expected to see the number eight where someone with red green deficiencies may have seen three on plate three a normal person would see a six whereas people such as myself would see a five on plate four a normal person would visualize the numbers 29 whereas here the red green color blind deficiency is going to show up with the number 70 again we're changing more again on plate five a normal person would see 57 was those with red green deficiencies would see 35 plate six would show five in a normal person and two if there's a color vision problem plate seven would show three for a normal person and five with color deficiency plate eight would have 15 for normal individuals and 17 if there's a color vision problem plate nine should um have 74 scene with normal vision and 21 with red green color deficiencies we're going to column two plates 10 and 11 12 and 13 14 and 15 16 and 17 now we asked you to go over to the second column here for plates 10 to 17 this is because here people with color deficiencies should not have been able to see anything so on plate 10 a normal person would see two plate 11 they would have seen six plate 12 they'd have seen 97 plate 13 they'd see 45 plate 14 they'd see five plate 15 there'd be seven plate 16 they perceive the number 16 as well plate 17 they' perceive 73 18 and 19 20 and 21 and now we're going to flip the tables for those of us with color deficiencies we should see something on plates 18 19 20 and 21 whereas those normal uh Vis people wouldn't see anything on plate 18 I'd expect someone with red green color deficiencies to see the number five on plate 19 they'd see number two on plate 20 they'd see 45 and on plate 21 they' see 73 so having completed those um plates we should know whether or not you've got any problems with your color vision if you've scored over 17 congratulations your vision's normal if you've scored 13 or under Welcome to My Color Blind Club but if you are in my club we now have to do some additional tests so we're going to go forward now to look over plates 22 to 25 and they're going to determine what type of color vision we have however this isn't just for those of us with color deficiencies those who have Tri chromia so normal color vision can also look at those plates because you will perceive different numbers from us we're going to do the same again we're going to show you the um plates only for brief 3 seconds and I need you to write down what it is you see as clearly as you can see them 22 and 23 24 and 25 so these plates 22 to 25 will allow us to determine whether or not you have a protan color vision deficiency IE a problem with the red cones or a dutan color deficiency I have a problem with your green cones so on plate 22 a normal individual would see 26 so if you had a red deficiency I a protan type deficiency a strong uh signal will be seen for the number six but if you had only a mild color deficiency in red that would show a weak two and a stronger six if you had a dutan or green color deficiency on plate 22 we'd have expected a strong two and a mild uh color deficiency would have a strong two and a very weak six on PL 23 a normal person would see 42 but the protan a red deficiency would have a strong two and if it's a mild red deficiency would' expect a weak four and a strong two a dutan deficiency so green color deficiency would have a strong four and if it was a mild green deficiency would' have a strong four and a weak two on plate 24 a normal individual would see 35 with a protan red deficiency if it was a strong deficiency would show five with mild having a weak three and a strong five so the dutan type green deficiency would show a strong three and if it was a mild deficiency would have a strong three and a weak five our final plate there plate 25 and number with 96 will be seing with normal vision our strong red deficiency would so six and our mild red deficiency would show a weak nine and a strong six our strong green color deficiency would show nine and our mild green color deficiency would show nine with a weak six well that's completed the isihara chart let's have a look what's actually happened so as we said if you've scored uh 17 or over you're fine if you've scored under 13 you've got your color deficiency and we've asked you to look at uh plates 22 to 25 to determine what's going on with the color deficiency well there we go so that wraps up how to use the ishihara chart and a bit of a background on color vision deficiencies if you found it useful please consider subscribing to the channel and please give it a like so that YouTube knows that we're here with that in mind I'll see I'll say Cheerio and we'll see you in the next one take care all [Music] [Music] you