hello everybody my name is yujin in this video i will help you out to understand human eye better i have prepared um exercises for you if you wish to download and print it out please help yourself to click the link in description box below so i guess without further ado let's go [Music] okay ladies and gentlemen let's do this so uh in your whole chapter one there is a lot of subtopic there is a lot of organs as well so i guess um i is one of the one of the topic where most of us struggle to especially especially remember that the labor links right so many of them and it's all around the eye and we have functions as well so i'll go through it quickly with you um to make sure you get an idea of the 2d picture and i'll show you how does it looks like in a 3d picture okay so human eye the sense of your eye it's called the sense of sight that's how you see things right sense of sight okay and the stimulus of your eyes will be light light is the thing that actually stimulates your eye receptors so that you'll be able to see things okay so let's get straight into the labeling so this is what i'll do i'll cut the eye into off right the front part and the back part so i would like to start with the back part and actually we will have three layers so we start off with very simple um sequence which is three layers okay there's three layers at the back of the eye i mean throughout the whole eye but we're doing at the back of the eye so three layers sclera outer layer choroid the middle layer and wrapped it now which is the inner layer which is the part where uh you sense like okay and we have two spots yellow spots which is called the fauvia which is the most sensitive part of your eye and we have blind spot which is the least sensitive part of your eye i should say there is no photoreceptor that means if image falls on blind spot there will be no image syn or no image found okay and we have optic nerve the wire to the brain and um there you go eye muscle that's negligible don't worry about that so we have three layers two spots and one wire that's it we're done with the back part okay right let's move to the center so there's this jelly at the center of your eye which is called the vitreous humor okay be aware of your spelling vitreous humor okay then move on to the front part okay starting from the outer to the inner i know it's very messy and you know there's a lot of layers please go through this with me i'll go through uh from the front uh to in to inwards okay so let's start off with the outermost layer which is called the conjunctiva but in fact the conjunctiva is actually just the top part here and the lower part here okay right which is at the white part of your eyeball right above the black color dot below the black color dot okay that's called conjunctiva right move on to cornea which is the first layer the front layer of your eye okay and then into this empty area which filled with fluid or liquid it's called the acoustima it's a jelly jelly lemon okay transparent right then down into your pupil which is the hole where allows light to enter and then the iris which is as asian we are in brown or dark brown or black in color with our iris okay that controls the size of the pupil open or closed or bigger or smaller okay then moving moving into your eye lens okay eyelands are hold in place by suspensory ligament which is like a clip okay to hold them in place and ciliary body is like a muscle okay which is right here uh that function to actually uh control your eye lens as well together with suspensory ligament we'll get into the function later on all right there you go that's it that's the that's the way usually how we remember so break it down into two parts the back part you settle the back part already then you move to the front part right don't struggle to like memorize everything one shot so cut into half go for the behind part when you're done with the behind part repeat to yourself and go to the front part okay from the inner to the um sorry from the outer to the inner part of the eye yeah all right so let's get into the 3d model of the eye so let's look around of what we have okay right so let's start off with the three layers that we were talking about so we have the first layer which is called the sclera second layer which is uh choroid and the third layer which is called the retina all right as easy as that and remember we have two spots behind so we have the uh yellow spots the most sensitive part of the eye and we have blind spot the least sensitive part of the that is also the beginning of the uh optic nerve actually do you realize that yeah saw that okay so hence there's no photoreceptors there and that's also the beginning of uh nerves that will transmit impulses to your brain hence it's also called a blind spot because it's not sensitive to light yeah okay there you go then we have optic nerve so three layers two spots and one optic nerve okay then of course the center part we have the vitreous humor which is the jelly lah nothing much okay uh then let's go to the front part of the eye so we have cornea obviously the first layer remember we'll start with the outer layer all the way into the inner layer okay so corona if you could uh if you could peep through the gap you see that after the cornea that will be the acoustimer right which is unfortunately unable to label that for you here which is right inside right after the cornea okay there you go so let's put that away right then that will be your pupil the black color hole that allows light to enter your eye through this hole okay and we have the iris which is to control the size of the pupil iris okay uh maybe let's take a look from the other part okay let's hide the vitreous humor so this is your eye lens right after your pupil will be your eye lens and this round circle that you're looking at this is your celery body or we call it as cilary muscles yeah and this tiny little fibers that you're looking at and in blue color that is also what we call a suspensory ligament suspensory although it's labeled here as zonular fiber right right on top there okay but we you know syllabus cause suspensory ligament that's actually to hold the lens in position okay there you go um what else i guess pretty much that's what we need to remember in our silly birth okay no problem i hope you get better idea of the view of the eye and all the layers and from the front all the way to the back okay cool so let's get back to our material right so functions that i roughly mentioned to you already just now okay maybe we can take a quick look so sclera is to actually protect and maintain the shape of the eyeball which is the first layer which is the white layer that you you are looking at now all right uh choroid is the second layer which consists of blood vessels it is actually to supply nutrients and oxygen to the eye okay and retina is the sensitive part of your eye or also the receptors of your eye which is to detect light and then it will transfer imbalances to the brain okay right and also retina has two very special type of cells which is called the cone cell which is to see color and wrought cell to see in black and white or in dim like there's two types cone for color remember okay rod for black and white okay so cornea the first layer of your eye that's to uh refract light onto the retina okay conjunctiva which is the around it okay that's to protect the sclera iris control the size of the people remember that one i show you pupil is the center part that uh to allow light enter the eye okay so eye lens like like all our lenses that we have like spectacles that we wear that's to refresh and focus this light to form sharp image on the retina okay so uh celery body that's to contract and relax the thickness of the island so the cilary body is the round thing that i showed you just now okay and suspensory ligament are all the fibers i showed you just now okay still hold the eye lens in position right across humor the jelly which is right after the cornea because human uh that's to maintain the shape also helps to focus the image okay to the eye and vitrous human which is the bigger jelly at the center of the eye which makes up the almost a lot of the eyeball okay that's called virtuous humor let's do focus image also and to maintain the shape so very similar in function okay yellow spot is the most sensitive part of the of the eye okay and blind spot is the part where not sensitive to light because there's no photoreceptors okay an optic nerve that's your wire to send impulses to the brain carry nerve impulses to the brain okay all good all right of course this uh actually takes time to takes time to memorize or to get into your head so probably have to go through a few times to make sure you know um all the functions properly which is in your textbook anyways okay right so i was mentioning just now wrought cell it's um just to get you to look at the picture a bit rock cell is the longer one that's quite called rod cell cone cell looks like a like a ice cream cone okay so it's called cones also remember cone cell for color yeah rod cell for black and white that's it all right no problem okay so uh mechanism of sight which is how light enters your eye okay or it's more like what we say like um the journey of the light it's like from the outside of your eye all the way in to your antenna so that's like a sequence that's like a journey of it it's called mechanism of light a mechanism of sight okay so light from object okay is reflected right from the object when light is on or when there is light uh the light is being reflected by the object to your eye so the first which is your cornea to achieve humor which is the jelly of the cornea to people the black color hole eye lens to the bigger jelly to the rectina and to the nerve to your brain that's it easy maybe i could quickly show you again how it works okay so let's probably travel through the eye as uh light wave or as light okay so this is the sequence so starting off with um let me go nearer okay so starting off with cornea okay we're at cornea now right so right after cornea okay it's it's very thin so kick it right oh right now we are in the acoustima okay then look at this black hole here this is your pupil right iris is around it so people go into it i think we're in islands now okay maybe let's get through it and take a look again yeah there you go we were at islands just now all right and go all the way to retina and retina will go all the way to optic nerve okay okay we're right at optic nerve now you get you get the idea right of i'll like travel okay so that's pretty much like that so quickly we look through the sequence again hopefully you get a better idea so cornea to a consumer which is the um jelly or the fluid right after cornea to black hole pupil to eye lens to the vega jelly and then to retina which i show you and uh into the optic nerve to the brain so this sequence is very important please make sure you remember that okay oh right the next thing to go to it's called optical illusion you know sometimes it's not the problem of your eye it's actually sometimes the problem of your brain that is not interpreting correctly of what you see like it's an argument between your eye and your brain your eye says like that what i see is then no i don't think so so when this happened we call it as optical illusion so optical illusion uh occurs when we see what we see is different from the actual situation okay these occur because what we see it's not only dependent on our eye but also on how our brain interpret what the eyes sees okay so no problem usually the image form is accurate but sometimes bring up problem okay so brain got problem couldn't translate or couldn't interpret correctly so i have examples for you here but if you're interested for more go ahead and google optical illusion there's so many of them for you to test out your eye and make your eye and brain argue if you want to see that happen go ahead and google and try out different tests different type of tests and uh let your eye and brain argue each other okay so for example a and b c and d it looks like a and b is longer but actually not actually the same length because of the arrow it makes you feel like they are different okay and same goes to this e and f should be straight in line but if you concentrate at the center red dot it looks like they are bending optical illusion due to the lines okay all right last we have this looks like there is um curved line in between but that's actually not it's just how the straight lines are being arranged okay that makes it looks like there is a line right there you go okay the next part will be your vision defect so we have three defects we have short-sightedness we have long certainness we have astigmatism so shock sadness means what means um you can see things that are near but you couldn't see things that are far okay so distance object blur near okay so lens to take eyeball too long that could be the reason so remember this when we say short sightedness we got opposite yeah short-sightedness lens to take eyeball too long you get what i mean right shots shots at short side short side short-sightedness i bought too long and lens too thick is that all right okay so that's usually how we remember so what happened is when lens two take or eyeball too long the image actually forms too early we say before the retina too early yeah or when eyeball is a bit too long oblong so it forms too early so how do we solve we wear spectacles with concave lens which is most of us who wear spectacles now your lens should be concave lens that actually opens up the light ray and imagine like it's shooting it further when they open up okay shooting it further to touch the point behind yeah okay so the function of the concave lens is actually to block the image further okay no problem there you go so what you have to remember is uh what happened the condition which is what you can see and what you cannot right and then also the the causes which is too tight and too long and what type of correction you must have to to wear as spectacles okay next one long sidedness so long suddenness opposite obviously means you can see far things clearly but you couldn't see near things okay no problem right that's the reason okay too thin too short so as i mentioned we go opposite long sidedness then it will be eye lens too thin and eyeball too short okay no problem that will be opposite okay so what happened is it goes over though like over the eyeball it forms over the eyeball so hence this is what we write after the retina you have to bring it nearer right so when you have to bring it nearer we wear convex lens which is maybe your grandma grandpa maybe your parents you know sometimes when they see when they read things they have to push it far whether okay oh okay right read newspaper okay you know when they do this others because when it's too near to them right it forms over their eyeball couldn't see they have to push it away unless they wear the the correct spectacles then they can see clearly right so the the reason of the convex lens or the purpose of the convex lens is to close it up just now it's opening up the light right now it's like to converge okay to close it up so it could hit the retina at the right spot okay there you go that's basically what are the two lenses for all right and the last one be astigmatism and stigmatism means you will see a lot of reflection of light a lot very bright lights or like there's a ring of light around the light bulb or the light source well the reason of that is because your cornea is uneven remember cornea the first layer of your eye it's uneven so it's uneven right the refraction also uneven hence it becomes multiple um image form so very blurred image okay so image form not evenly before the retina so usually what we do is we wear cylindrical lens so this is how it looks like cylindrical lens so pretty much that's like a not very difficult like a summary to memorize uh everything in a box very convenient so please make sure you go through that okay and how to wear the correct lenses okay then i guess that's pretty much fine next one will be how to protect your eyesight a very general stuff so take a look if you want pause the video very straightforward so um that's it for the eye section of your chapter one okay let's get into some exercises to uh to see if we understand about the topic today okay so labeling i guess uh i'm gonna leave that to you because you need to figure out your labeling properly make sure you remember all of them and then you shall fill up um the label links for yourself so i'll leave that to you okay so next one i think we will start off with this let's draw lines to the correct answer okay so iris what's iris r is the the color part of your eye that's to control the size of the pupil very straightforward ciliary muscle okay slurry muscles are to out to control the thickness of the lens the other one is called suspensory ligament suspensory ligaments to hold the lens yeah next one choroid choroid is two the second layer that i remember to supply oxygen and nutrient to the eye okay and uh conjunctiva which is the the the part white on the white color part around the corner that's actually to protect the sclera as well as to protect the cornea so in this case we will go for this okay all right question c on the retina there are two dots known as the blind and the yellow spot so what a difference so very straightforward yellow means the most sensitive blind means not sensitive at least you remember the story be able to form sentences yeah yellow spot is the most sensitive area towards light because it contains a lot of receptors where blind spot is the area without any light receptor okay so you couldn't see anything on it if image form on blind spot right question d two types of photoreceptor found in retina remember the color one c cone cell c for color okay and rod cells for black and white or low light intensity very straightforward okay number two this is optical illusion right question do a b and c d parallel means are they like straight and same length so far it believes that both are parallel but as i'm saying i don't think so so how do we prove that they're actually indeed the same length or they are parallel to each other well the best way is to measure the distance between two of them that means that you take your ruler and measure here to here measure here to here measure here to here if all them are the same length or same um distance apart means for them straight up and parallel huh parallel to each other if it's curving uh if it's curving uh then the distance will be different right make sense so this is our question a bit tricky because it's thinking question or we call that k but question we have to use your basic understanding understanding to to answer right two parallel lines have the same distance ah so measure a c b d line if distance are the same two lines parallel okay this is like stating the steps that you're going to prove so it looks uh non-parallel due to um your eye and your brain is arguing like you know i think it's straight up then your brain said no i don't think so it's curved then your eye says no it's straight obvious so yeah they will argue for the rest of their life okay right number three amira has vision problem she met optometrist diagram below shows the conversation okay your eye cornea uneven keyword ladies and gentlemen very straightforward it's actually not very difficult as you think so if you remember key words if you remember important part of that particular topic you probably can see see through it and you can actually know what you need to answer but now the problem is to to you know from sentences which you have to work towards that okay so cornea uneven thing keyword comes out already okay so what's suitable treatment so cornea i'm even it has to be astigmatism remember okay so astigmatism the correction needs to wear so see your answer is here astigmatism checking one mark and cylindrical lens touching two marks this is how you get your answer correct okay no problem is that all right now um go ahead and download this if you need to just to get yourself to write on the papers all right i hope this video helped and if you like the video give me a thumbs up if you would like to share with your friends please share with your friends and i guess i will see you in the next video right bye guys [Music] you