Hi, I'm Meris, and in this video, I'm going to be talking to you about the type, function, and assessment of cranial nerve number II, optic. I'm going to be following along using our Health Assessment flashcards. And these are available on our website, leveluprn.com, if you want to grab a set of these hard cards for yourself. Or if you are somebody who prefers a digital product, I would invite you to check out Flashables, which are our digital flashcards. It's awesome. You can have them in your pocket everywhere you go.
All right, let's get started.
So we are talking today about cranial nerve number II, which is the optic nerve. I always remember you've got two eyes, so cranial nerve number II is responsible for your sense of vision. So this is the nerve that controls visual acuity, which means it is a sensory nerve. There is no motor function to the optic nerve. The only job this nerve has is to see, okay, just to sense that visual input that's coming in. Now, we can assess this in a number of different ways, but there's four things that we're really looking for when we are assessing cranial nerve number II. We're looking to assess far vision, near vision, color vision, and peripheral vision. So I'm going to explain to you the assessment tests that we can do for each of those categories.
So when we are assessing far vision, this is a test called the Snellen test. And when we do a Snellen test, we're actually going to position an adult patient 20 feet from the chart. And you are familiar with this chart. This is that very classic chart that lives in your eye doctor's office that has a big E at the top. That's the Snellen chart. And this is a chart that has these letters that start off really big, and then they get much, much smaller as each line goes on, progressively smaller. And we're going to position our adult patients 20 feet away. Pediatric patients would be 10 feet away. We're going to position them 20 feet away from that Snellen chart while they are wearing their glasses or corrective lenses, if that applies to them. And then we will have our patients cover one eye at a time. You will very commonly see that at the eye doctor, they actually have a special paddle that you will hold up in front of your eye. But we're going to have our patient cover up one eye at a time. And then they're going to read the letters on each line. They're going to start with the top line, and they're going to keep going down. And we are going to stop our patient when they miss 50% or greater of the letters on one line. That's where we're going to cut them off. Then we will do the other eye, right? We're going to cover one, and then we're going to cover the other, and we'll go through that chart again. That is assessing for far vision.
How do we assess for near vision? I'm so glad you asked. We're going to do a test called the Jaeger test. And with this, we use a special card called a Jaeger card. And it's kind of like this. It's a card that has some text written on it. And all we're going to do is have the patient hold this card about 14 inches away from themselves, and that's about an arm's length away from their field of vision. And they're going to maintain their glasses or corrective lenses in place if applicable, because again, we are trying to assess the function of the cranial nerve, not if our patient needs corrective lenses in this case, right? So we're going to have them wear the corrective glasses or lenses and then read the smallest block of text. So you're going to have a card that has different sizes of text, and we're going to ask them, read the smallest block of text that you can comfortably read from an arm's distance, right, from 14 inches away. And that's going to help us to assess their near vision.
Now, when we're talking about color vision, when we are assessing for color blindness, we will use something called the Ishihara color test. Ishihara color test is going to be a series of circular plates that are made up of circles, different colored dots. And those colored dots in the Ishihara test, they are specifically created to be impossible for someone with certain types of colorblindness to be able to look at these and distinguish the number that is written inside them. So for instance, you might have an Ishihara test that the number is 26. And I am not a colorblind person - that is not a disability that I have - so I would be able to look at that plate and say the number here is 26. However, if I cannot identify it, if I say I don't see that number, or perhaps I see a different number, that's going to give some valuable information. Each plate looks for a different type of colorblindness. Remember that there are multiple types. There's red-green color blindness, but that's not the only kind. So if we pass the red-green, that's great. But we've got to look at all of them to ensure that we do have color vision.
And then lastly, when we're talking about peripheral vision, peripheral vision can be assessed with something called the confrontation test. And why is it called confrontation? It's because you're getting in their face, right? You're confronting this person. Think about a confrontation when you're getting in somebody's face and you're yelling and whatever kind of unkind thing you're doing, right? That's how you are going to approach your patient for confrontation. So when you do the confrontation test, you're going to have your patient cover one eye and look at your nose. You're going to get really close up to them, right? You're going to say, cover one eye and look at my nose, right? And then we're going to bring our fingers up. And we're going to say, tell me how many fingers I'm holding up, right? And we might do like here and then here and then here and then here. Your patient should be able to see those fingers and identify the numbers that you are holding up using only their peripheral vision. And then we'll just repeat that test with the other eye covered. But again, remember, confrontation, you're confronting them. You're getting right up in their face. And then we're going to do the how many fingers am I holding up, right? Confrontation is going to assess for peripheral vision.
All right, now I'm going to test your knowledge of some key facts I provided in this video with our quiz questions. How far should the nurse position an adult patient from the Snellen chart? 20 feet from the chart. What is the nurse assessing when performing the confrontation test? Peripheral vision. Which test is used to assess a patient's color vision? The Ishihara color test.
All right, that is it for this video. I do hope that you found this review useful. All right, I'll see you next time. Happy studying.
