Muscles of the eye - extraocular muscles and movements

Summary

This educational video script delves into the complex anatomy of the human eye, focusing on the extraocular muscles and their role in eye movement. It explains the six muscles that control eye movement, their functions, and how they interact with the three axes of the eye. The script also discusses the importance of eye movement for maintaining visual stability and focusing on high-resolution areas of the retina, like the fovea, during head movements. It provides a detailed yet accessible explanation of the intricate mechanics behind our ability to see clearly while in motion.

Takeaways

• 🧠 The human eye has a complex anatomy with more anatomy per cubic centimeter within the orbit than anywhere else in the body.
• 👀 The script focuses on the movements of the eyeball, specifically the extraocular muscles and their functions.
• 💪 There are six primary extraocular muscles that move the eye: the medial and lateral rectus, superior and inferior rectus, and superior and inferior oblique muscles.
• 🔄 The eye can move around three axes: horizontal, vertical, and anteroposterior, allowing for a range of movements including abduction, adduction, elevation, depression, and rotation.
• 👁 The primary function of eye movement is to keep an object of interest focused on the fovea, the high-resolution part of the retina, especially during head movement or when tracking moving objects.
• 🔄 The superior oblique muscle has a unique path, passing through the trochlea to change direction before inserting into the eye, contributing to both depression and intorsion.
• 🔄 The inferior oblique muscle is short and runs from medial to lateral, causing extorsion when it contracts.
• 🤝 Muscles rarely work in isolation; they often work in pairs or groups to produce coordinated eye movements.
• 🔍 The script emphasizes the importance of understanding the axes and the direction of muscle pull to comprehend the actions of the extraocular muscles.
• 📚 The video script is educational, aiming to help viewers, possibly medical students or health professionals, understand the complex anatomy and function of the eye's movements.
• 🎥 The use of models and visual aids is suggested for better comprehension of the three-dimensional aspects of the eye's anatomy and muscle actions.

Q & A

What is the main topic discussed in the script?

The main topic discussed in the script is the anatomy and function of the extraocular muscles and the movements of the eyeball.

How many extraocular muscles are there, and what is their primary function?

There are six primary extraocular muscles that move the eyeball, and their primary function is to control eye movements, allowing us to focus on objects as we or they move.

What are the names of the four rectus muscles?

The four rectus muscles are the lateral rectus, medial rectus, superior rectus, and inferior rectus.

What are the two oblique muscles, and how do they differ from the rectus muscles?

The two oblique muscles are the superior oblique and inferior oblique. They differ from the rectus muscles in that they run from anterior to posterior and have a pulley system, which changes the direction of their pull on the eyeball.

What is the trochlea, and what is its function in the movement of the eyeball?

The trochlea is a pulley-like structure through which the superior oblique muscle passes, changing its direction and allowing the muscle to contribute to the rotation of the eyeball.

How do the axes of the eyeball relate to its movements?

The eyeball can move around three axes: the horizontal axis for up and down movements, the vertical axis for medial and lateral movements, and the anteroposterior axis for rotation.

Why is the fovea of the retina significant for eye movements?

The fovea is significant for eye movements because it is the area of the retina with the highest density of cones, providing the highest visual resolution, and eye movements help keep objects of interest focused on the fovea.

What is the primary reason animals, including humans, move their eyes?

The primary reason animals move their eyes is to keep objects of interest in focus on the high-resolution fovea of the retina, especially during movement.

How do the extraocular muscles work together to produce eye movements?

The extraocular muscles work together in various combinations to produce eye movements, often with one muscle having a primary action while others assist or counteract to fine-tune the movement.

Why do the described movements of the eyeball by each muscle differ from the H-shaped pattern used in clinical exams?

The described movements differ because in clinical exams, the H-shaped pattern is used to isolate each muscle's function, whereas natural eye movements involve the muscles working together and overlapping in their actions.

What is the significance of the orbit's shape and direction in relation to the eye muscles?

The orbit's shape and direction are significant because they influence the paths that the extraocular muscles follow, which in turn affects the directions and types of eye movements they can produce.

Outlines

00:00

🔍 Anatomy and Movement of the Eyeball

The script introduces the complex anatomy of the eye's orbit and the intricate movements of the eyeball. It emphasizes the high density of anatomical structures within the orbit and the importance of understanding the extraocular muscles' arrangement and function. The speaker explains the need to consider the angle of the muscles and their spatial relation to the eye's line of sight. The script also discusses the three axes of eye movement and how muscles are linked to their attachments to facilitate these movements. The importance of studying muscles in pairs is highlighted, as they often work together during eye movements, which is a common theme in the body's muscular system.

05:01

💪 The Extraocular Muscles and Their Functions

This paragraph delves into the specifics of the six extraocular muscles responsible for eye movement, excluding the levator palpebrae superioris. The muscles are described based on their anatomical positions: the four rectus muscles (lateral, medial, superior, inferior) are straightforwardly named and function, while the two oblique muscles (superior and inferior) have more complex paths, including the superior oblique's unique pulley system, the trochlea. The paragraph explains how these muscles work in conjunction to move the eye along the three axes of motion: horizontal, vertical, and anteroposterior, allowing for a range of eye movements including abduction, adduction, elevation, depression, and rotation.

10:01

🌐 Understanding Eye Rotation and Its Importance

The script explores the reasons behind the rotation of the eyeball, such as maintaining the horizon's level during head tilts and counteracting the secondary effects of other muscles' actions. It explains how the superior and inferior rectus muscles, due to their paths across the eye's equator, can cause both elevation and adduction, while the superior and inferior oblique muscles, with their anterior-to-posterior trajectory, can induce both rotation and abduction. The paragraph also touches on the complexity of these muscles' actions and how they contribute to precise eye movements, often working in concert to achieve a singular visual goal.

15:05

🔄 The Complex Actions of Oblique Muscles

This section focuses on the superior and inferior oblique muscles, detailing their actions and how they interact with each other. The superior oblique's path from medial to lateral causes intorsion (medial rotation), while the inferior oblique, moving in the opposite direction, results in extorsion (lateral rotation). Both muscles, when working together, can cause abduction. Additionally, due to their anterior-to-posterior orientation, the superior oblique can assist with depression, and the inferior oblique with elevation. The paragraph underscores the overlapping actions of these muscles and the coordinated effort required for eye movements.

20:09

🧠 Clinical Implications of Eye Muscle Actions

The script discusses the clinical examination of eye muscles and the challenges of isolating individual muscle actions during tests. It explains why the movements observed during a cranial nerve exam differ from the natural actions of the extraocular muscles. The speaker uses the analogy of making a fist to illustrate the cooperative nature of muscle movements in the body, including the eye. The paragraph concludes by emphasizing the importance of understanding the axes of eye movement and the anatomical orientation of the muscles to grasp the full complexity of ocular motility.

🎯 The Purpose of Eye Movements in Focusing

The final paragraph addresses the fundamental question of why we, and other animals, move our eyes. The primary reason is to maintain the focus on an object of interest on the fovea, the high-resolution part of the retina, especially during movement. The analogy of a GoPro camera on a gimbal is used to explain how the extraocular muscles stabilize the visual field, akin to a gimbal stabilizing a camera during motion. The script concludes by acknowledging the complexity of the eye's anatomy and the effort required to understand it fully, promising further exploration of the topic in future sessions.

Keywords

💡Anatomy

Anatomy refers to the branch of biology concerned with the structure of organisms and their parts. In the context of the video, it is used to describe the complex structure within the eye orbit, emphasizing the high concentration of anatomical features in a small space, which is crucial for understanding the intricate movements of the eye.

💡Extraocular muscles

Extraocular muscles are the muscles that control eye movement. The video focuses on these muscles, explaining their roles in the movement of the eyeball. There are six primary extraocular muscles discussed, each with specific functions that allow for the complex and precise movements of the eye.

💡Axes of movement

The axes of movement are the theoretical lines around which the eyeball can rotate. The video explains that the eye can move around three axes: horizontal, vertical, and anteroposterior. Understanding these axes is essential for comprehending how the extraocular muscles work together to enable various eye movements.

💡Orbit

The orbit refers to the bony structure that houses the eye and the muscles that move it. The video script describes the orbit's shape and how its structure influences the direction and arrangement of the extraocular muscles, which is vital for the eye's mobility.

💡Trochlea

The trochlea is a small pulley-like structure in the orbit through which the superior oblique muscle passes, changing its direction. The video mentions the trochlea as a key anatomical feature that allows for the superior oblique muscle's unique action in eye movement.

💡Rectus muscles

Rectus muscles are a group of four straight muscles named for their directionality: superior, inferior, medial, and lateral rectus. The video explains how these muscles work to move the eye in straight lines, either up and down or side to side, in relation to the eye's axes.

💡Oblique muscles

Oblique muscles, specifically the superior and inferior oblique muscles, are discussed in the video as having a different orientation compared to the rectus muscles. They are responsible for more complex movements, including rotation of the eye (intorsion and extorsion), and they contribute to the eye's abduction and adduction.

💡Abduction and Adduction

Abduction refers to the movement of the eye away from the nose, while adduction is the movement towards the nose. The video explains how specific extraocular muscles are responsible for these movements, with abduction being associated with the lateral rectus muscle and adduction with the medial rectus muscle.

💡Elevation and Depression

Elevation is the upward movement of the eye, while depression is the downward movement. The video describes how the superior rectus muscle is responsible for elevation and the inferior rectus muscle for depression, both essential for looking up and down.

💡Intorsion and Extorsion

Intorsion and extorsion refer to the rotational movements of the eye, with intorsion being a medial rotation and extorsion a lateral rotation. The video explains the role of the superior and inferior oblique muscles in these rotational movements, which help maintain the horizon level as the head tilts.

💡Fovea

The fovea is a small depression in the retina that provides the sharpest central vision. The video concludes by explaining the importance of eye movement in keeping objects of interest focused on the fovea, allowing for high-resolution vision as we or our surroundings move.

Highlights

Anatomy of the orbit is complex with more anatomy per cubic centimeter than anywhere else in the body.

The lecture focuses on the movements of the eyeball and the role of extraocular muscles.

Six extraocular muscles are discussed, with the seventh, levator palpebrae superioris, excluded from the discussion.

The importance of considering the angle of muscles and the space within the orbit is emphasized for understanding eye movements.

Three axes of eye movement are identified: horizontal, vertical, and anteroposterior.

The concept of muscles working in pairs for eye movement is introduced.

The anatomy of the orbit is described as a flaring shape, like a pyramid, with implications for muscle direction.

The rectus muscles are named and their straightforward paths and functions are explained.

The superior and inferior oblique muscles are detailed, including their unique paths and pulley system.

The primary actions of each muscle are described in relation to the axes of eye movement.

The overlapping actions of the muscles and their cooperation for precise eye movements are highlighted.

The role of the superior oblique muscle in causing intorsion and its complex path is discussed.

The inferior oblique muscle's role in causing extorsion and its relationship to the eye's abduction is explained.

The clinical examination of eye movements and the H-shaped test for cranial nerves are mentioned.

The reason for eye movement in humans and animals is explored, focusing on the fovea and high-resolution vision.

The analogy of a gimbal is used to explain the stabilization of the visual field during head movement.

The lecture concludes with an encouragement to study and understand the complex coordination of eye muscles.

Transcripts

[Music]

[Applause]

[Music]

[Music]

v/o there is what a lot of anatomy

within the orbit I'm gonna handle each

bit of an atomy in bits will break up

into smaller chunks I'm not known for

being concise so that's gonna be a good

thing if I break it up into chunks

you'll be anyway let's not go off on a

tangent the ophthalmologists love to

tell me there is more anatomy per cubic

centimeter within the orbit than

anywhere else in the body sounds right

what we're going to do today is we're

going to look at the movements of the

eyeball so we're going to look at the

extraocular muscles we have two things

we really need to consider the the angle

at which the muscles are running within

the orbit and the space of the orbit in

relation to where we're actually looking

you'll see what I mean when we get there

and we need to consider the three axes

about which the eyeball can move and

then we need to link up the muscles and

where they attach and then it starts to

make sense but let's hear Sara why do we

move our eyes we'll come back to that

again why do we move our eyes

[Music]

[Applause]

okay so how we going to do this I have

got only two models today I have the

simplest model of the eye that I have

we're going to look at the orbit itself

in the shape of the orbit I have another

video about the bones of the orbit and

we're going to look at each of the

individual muscles there are six extra

ocular muscles within the orbit there

are actually seven because levator

palpebrae superioris gets included as an

extra ocular muscle but I'm not going to

talk about that today I'm just going to

talk about the six muscles that move the

awning people will look at the muscles

will look at how they're arranged that's

the easy bit it's pretty easy to see

what each one does in isolation

theoretically but what we need to

consider are the three axes that the

eyeball sits within and how those

muscles cross those axes and how they

pull the eye in different directions and

one we might look at each muscle in turn

we need to think of them in pairs

because when they work in pairs they do

something else

rarely in the body the muscles work in

isolation every time we make a movement

we're using lots of muscles to make that

movement it's exactly the same in the

eyeball but we take it all for granted

when we've done all that we can consider

why are the described movements of the

eyeball by each muscle different to the

way in which we look at the muscles when

we test them doing a clinical exam of

the eye or the cranial nerves of the eye

first things first you're aware that

your pupils are looking in roughly

parallel directions right there they're

side-by-side okay you get convergence

from what have you is you looking

closely but essentially your pupils are

looking in this direction they're both

looking along those axes right they're

parallel but right sorry

it's a plastic skill

when we looking sonically all of it so

if you imagine that the apex of the

orbit is at the back the orbit is

actually a flaring shape it's like a

pyramid in there right it's it's narrow

at the back

that's where everything comes in from

the brain from the cranial cavity and

then it flares out wasn't it easy to get

wider there's room for muscles and the

only ball and stuff so the apex at the

widest part that's where you've got the

eyeball but if you if you stick your

finger in there and you go from the apex

out through the middle of the the

opening of the orbit you see that the

orbits the two orbits aren't pointing in

that direction they're pointing in two

different divergent directions my point

is that while the the neutral position

of the eye has the pupil looking in that

direction the actual bony cavity is

running in this direction which means

that all of the extra ocular muscles

that are going to move the eye are also

running in this direction because

they're next to the the bony balls of

the orbit do you see now the eyeball

itself is suspended in place by a whole

bunch of ligaments or more have you so

they can it can it can rotate that's a

midsagittal section right so that's and

the eye the eye is looking that way

right but when we look at the orbit you

see the direction the muscles running

this running Inlet it's like this this

way ah so the the center of the the axis

of the orbit is actually out in this

direction which we consider the earth to

be in this direction

there's the eyeball you can see it kind

of sticks out from your bay a little bit

you know I've noticed your eyeball stick

out a little bit

there's trying to buy loads of

protective things and so on and so on we

can talk about other structures within

the orbit another day we're focused on

these guys these muscles now these

muscles are long and straight so four of

them are rectus muscles and they're

amazingly sensibly named so the rectus

is a it's a straight muscle and we

have the lateral rectus laterally we

have the medial rectus in here medially

we have the superior rectus up here

superiorly and we have the inferior

rectus doing the same thing under their

inferior Li how terribly sensible so

those are the four straightforward ones

let me have two obliques

and what's happening with the oblique

muscles is if I take off superior rectus

you can see here is the superior oblique

muscle a superior oblique muscle is

running from the back here all of these

rectus muscles and the superior oblique

run from this common tenderness ring

back here deep within the organ they've

run anteriorly from this that's an

anchor so the superior oblique muscle

runs along the bony edge of the orbit

and then when we get out here so here

there is a pulley the trochlea and we

talked about this when we were talking

about super alien for a trochlea nerves

when we talk about the trigeminal nerve

in sensory bits of the face now the

other and the reason that pulley is here

is because the superior oblique muscle

passes through the trochlea and changes

direction and then what it does is it

runs laterally across to insert into the

eyeball but also it runs from anterior

to posterior which is interesting right

so anterior to posterior and also medial

to lateral flat for superior oblique we

have down here we have the the inferior

oblique muscle and the inferior oblique

muscle is just a short muscle running

across here from medial to lateral it's

curving around with the eye it doesn't

have the long belly running all the way

down here it's just this bit here so we

have superior and inferior rectus

muscles medial and lateral rectus

muscles the superior oblique and

inferior oblique muscles those are our

six that are going to move the eyeball

now as I said the eyeball moves around

three axes we have

one axis here which might be the

horizontal axis and the only ball will

move like this with the horizontal axis

you look up and down and then we have a

vertical axis so the eyeball could pivot

left and right so you look medially and

laterally about the vertical axis but

then there's also an answer or posterior

axis running in this direction so not

where the pupil is not the direction the

pupils running in but along the axis

that the of the bony orbit and that

means that the young eyeball can also

rotate so we can we can give these

movements a number of names and they

might be similar to other parts of the

body so if we if we consider the pupil

if you move move the pupil who's doing

this all right if you move there though

really tiring if you need to move the

pupil laterally that would be abduction

your abduction your gaze your abducting

the eyeball whereas if you bring the

pupil immediately your adducting the

gaze just as if we were talking about a

limb where we have adduction and

abduction right and then we have we

might call raising the people to look up

elevation and we might call lowering the

pupil to look down depression and then

we have if we move the eyeball so for

considering the right eyeball and we

move it this way so that the top moves

medially that would become medial

rotation or in torsion and then if we

move the eye ball the other way rotated

that way that would be lateral rotation

or extortion now we're going to talk

about why we move the eye later once

you've hopefully figured it out but the

other most of these muscles I think it

you can you can see what they do they

lateral rectus if it pulls on the

eyeball it's going to pull it that was

going to abduct gaze right and we're

going to that in more detail in the

moment but if I'm talking about in

torsion and extortion why do we need to

rotate our eyeball well one reason is

that we keep the horizon level and as we

rotate our head because I think most of

the time you know your eyes at your

eyeballs aren't

Fuli level you often tilted one way or

the other so the ability to rotate your

only born a little way means you can

keep the horizon level as you tilt your

head you get to a certain point it

doesn't work anymore than the horizon

till it's right it all breaks down but

that's one reason for in torsion and

next torturing the eyeball

the other reason is that when we use one

muscle to pull on the eye because of the

way the muscle attaches in other way the

muscle runs and into attaches it might

also not just cause the eyeball to to

say elevate but also to rotate so then

we have another muscle that can rotate

the eyeball to counter that rotation so

that it doesn't rotate and in fact you

just look up instead of looking up and

rotating and getting double vision it

gets complicated quickly but that's the

principle we can rotate our eyeballs so

we can keep the horizon level as we tilt

our heads but also to counteract the

actions of other muscles right should we

crack on through these bad boys then

let's look at medial rectus and lateral

rectus first because they're probably

the most straightforward so here's this

is lateral so here's lateral rectus here

running from the common tenderness ring

lateral to the eyeball and it's staying

out against the bony edge of the orbit

it runs out here now look if we consider

the equator one equator of the eyeball

here so halfway along the equator of the

eyeball it's it's passing beyond that

equator so is going to the other side of

the eyeball I think it's pretty

straightforward what it does when this

muscle contracts it pulls on the eye and

causes it to rotate in that way so

lateral rectus causes abduction of the

eyeball medial rectus on the other side

very difficult to see but the principle

is the same there's medial rectus there

is doing the same thing as following the

bony edge of the orbit on the other side

and when that can that contracts again

it crosses that equator of the eyeball

so it pulls it that way so medial rectus

causes the angle of

what causes the eyeball to be adducted

so he look towards the nose so when

you're crossing your eyes you're using

you to medial rectus muscles and those

two are good that's it for those guys

really now if we look at superior rectus

and inferior rectus superior rectus runs

from the common tenderness ring through

along the roof of the orbit and then

again inserts into the eye it crosses

over that equator and inserts into the

eye so when it contracts it's going to

pull the line that away so superior

rectus will cause elevation of the

eyeball so we look up that superior

rectus inferior rectus then on the other

side which again is very difficult to

see but it's down it's down in there

again it's learning along the floor of

the orbit when inferior rectus contracts

it's again crossing the equator of the

orbit so it it pulls the the bottom of

the eyeball around so inferior rectus

causes us to look down causes depression

okay but there's more if we look at

superior rectus inferior rectus --is is

mirroring it the superior rectus is if

we consider the eyes looking this way

but the orbit is pointing that way and

the muscle is running with the direction

of the bony orbit the superior rectus

muscle is passing from medial to lateral

so it's it's not just crossing this

equator but it's also crossing this

equator what this means is that because

it's running from medial to lateral is

superior rectus and inferior rectus both

contract they can pull the eyeball that

away so they can also adduct the eyeball

if they work together this this vertical

axis is what we're pivoting around for

adduction and abduction and there's more

remember so we've talked about two axes

we've talked about the vertical axis

and the horizontal axis don't forget

that anteroposterior axis because these

muscles also run superior and inferior

to that anteroposterior axis and they

they cross over when they contract they

can also cause rotation of the eyeball

so again because they're superior so the

superior rectus muscle thing can also

cause in torsion OVI and the inferior

rectus muscle can cause extortion of the

eye I mean this is what people often

come across when they talk about the

primary secondary maybe tertiary

movements of different muscles they give

us superior rectus and inferior rectus

so I've saved superior oblique and

inferior oblique muscles now

the superior oblique muscle because it

crosses from medially two laterally it's

I think it's it's fairly obvious main

action is to cause in torsion so the eye

rotates this way rotates medially

because it yeah it's it's it's really

over the top there pulls the eye over

that way and then the inferior oblique

muscle because it's running in the

opposite direction there when that

contracts it's gonna it's going to pull

the eye that way so we'll get extortion

or lateral rotation of the eye so

superior oblique and inferior oblique

also work against each other now

I also said that these oblique muscles

run from anterior to posterior you see

look so the important thing is that it's

this this angle here is that the muscle

is is running across this axis and it's

going it's going across oh it's going

across to the other side of of this axis

alright and it's running from anterior

to posterior what that means is when

when superior oblique and inferior

oblique contract they're gonna pull this

part of your orbit this away right which

means that they're gonna pull the eye

outward so superior oblique

inferior oblique working together can

also cause abduction of the eyeball oh

my poor eyeballs and there's yet more

one last thing though really with these

guys because the superior oblique muscle

is running from anterior to posterior it

means it's also going to pull the

posterior part of the eyeball and

tearily so superior oblique can also

help with depression can also help with

pulling the eyeball down so you look

down and the inferior oblique likewise

because it's crossing in a similar

direction but in Reverse can also cause

elevation can can elevate the gaze you

look up so superior oblique causes in

torsion inferior oblique causes

extortion when they work together they

cause abduction so you look outwards but

they the superior oblique will also pull

the eyeball down a little bit will cause

depression and inferior oblique will

also pull the back of the eyeball up a

bit so they of course elevation really

really tricky but it's just my muscles

anywhere else in the body when you make

a fist you are using a lot of muscles to

make that fist some of these muscles are

contracting so you flex the fingers

right but other muscles got a relaxed

tool a flex the fingers if your finger

extensors were also contracting then

your fingers wouldn't move but more

importantly than that we have other

muscles going to the wrist that's the

the extensors of the wrist stop the

wrist from flexing which the finger

flexors are want to do and that's all

thing right so whenever we make a

movement we're actually using a lot of

muscles to make that movement and it's

the same in the eye we make these

incredibly precise incredibly accurate

movements and generally speaking these

muscles are working together to cause

those movements so so we might think

that a muscle has a primary action but

just like everywhere else in the body

you need to remember these movements

over the lap and they work together the

important that the important thing and

the hardest concept is in those axes

there that

the idea that the orbit is angled

outwards whereas our pupils and the

Ollie balls are looking parallel

forwards and that the muscles are

running with the orbit and they cross

over these equators to move the eyeball

when you add all that together and build

up then you can start to understand why

the different muscles have the different

actions if if you're studying medicine

or another health profession and you

you've studied the cranial nerve exam

you might wonder why the movements I've

just described are completely different

to the the h-shape you get patients to

follow when you're testing the cranial

nerves innervating these muscles and

we'll do the quickl nerves another time

we've done enough and the reason is

because as I just described the actions

of these muscles overlap with the other

muscles so you can't just I mean be

quite hard to to ask somebody to rotate

their eyeball right to see if superior

inferior oblique are working what you

need to do is you need to get the eye

into a position where that muscle is

isolated and when we're looking medially

the only muscle event can cause us to

look up to elevate the gaze is leak so

what we're doing when we're getting the

patient to follow this eight shape is

we're isolating each muscle as best we

can we can and then asking the patient

to perform a movement that only that

muscle can perform and making it do it

on its own if we start from the primary

position of the eye then we move we we

do all these movements we're using

multiple nuttin multiple muscles

together so of course like we asked we

say to the patient you know we always

you ask the patient to look laterally

and we say that we're testing lateral

rectus we're testing the abducens nerve

but I've just said that superior oblique

and inferior oblique muscles they can

also cause abduction of the eye so how

is that a useful test well really

lateral rectus

is the only muscle that can fully abduct

the I superior oblique and inferior

oblique will do a lil way but not the

same way and of course what you always

do is you're looking at both eyes and

you asking the patient if they get any

double vision and if they get to the

point where you know the eyes aren't

staying together and ones moving further

than the other than they start getting

double vision and you can start to work

out what's going on in the patient well

do cranial nerves another time we'll add

that on all right so I asked you why do

we need to move our eyes not just we not

just us but other animals why do animals

move our eyes have you thought for good

reason you may well know this the main

reason seems to be that you're probably

well aware that the retina detects light

but there's an area of the retina which

has greater sensitivity there's a higher

density of cones there so that's where

we can see in the highest resolution and

everything out here is kind of a bit

blurry right in the brain fills it in

and so on that's perception well the

reason we move our eyes is so that as we

are moving or as the thing we're

following is moving maybe pray or maybe

we are the prayer we're being chased or

we're just running and the reason we

move our eyes is it so that we can keep

the thing we're interested in focused on

the fovea on the the high res part of

the retina as we're moving as our heads

are moving or as it's moving

that's what serie he's my GoPro right

now if I am you know if I do that if I

if I move me go pull around like that as

I'm so I'm moving my head it's probably

ouch not too jerky but we get we get

this sort of action right we get a bit

of jerky video but if I stick my GoPro

in my gimbal and the job of the gimbal

is to kind of mimic what the extraocular

muscles do and as I move my head the

gimbal

keeps everything steady so that seems to

be the main purpose for all these extra

ocular muscles and the reason why we can

move our eyes so we can focus the

highway is part of our retina on the

thing we're interested in as we move

okay and that's it that's my explanation

I just used two models it's probably

going for me this is gonna take some

work if you've got it just like that are

you doing well this is going to take

some looking at and studying and

thinking about and then you'll get it

I've just I just laid you a bit of grain

work I've tried to make a couple of

explanations you're gonna have to think

about this and ideally look at models

and that sort of thing but hey you're

just gonna boil it down to whatever you

need to know anyway and forget the

details and write okay if this was

useful I've done well I kind of been

putting off the eye because there's so

much here but maybe we'll do some more

well we will do some more stuff in the

future much not sure when catch you guys

next time

[Music]

[Applause]

you