Orbit and Eye Anatomy

Question 1

What are the three layers of the eye?

Answer 1

Fibrous outer layer, uvea (middle layer), retina (inner layer)

Question 2

What makes up the fibrous layer of the eye?

Answer 2

Sclera = muscle attachment
Cornea = 2/3 of refractive power

Question 3

What layer of the eye is the vascular layer?

Answer 3

The uvea

Question 4

What are the parts of the uvea?

Answer 4

Iris = pupil diameter
Choroid = nutrition and gas exchange
Ciliary body = controls iris, shape of lens and secretion of aqueous humour

Question 5

What layer of the eye is photosensitive?

Answer 5

The retina

Question 6

What are the main three parts of the retina?

Answer 6

The macula, retina and optic disc

Question 7

Where is the anterior segment of the eye located?

Answer 7

In front of the lens

Question 8

What is the anterior segment of the eye divided into?

Answer 8

Anterior chamber = between cornea and iris

Posterior chamber = between iris and suspensory ligaments

Question 9

Where is the posterior segment of the eye located?

Answer 9

Behind the lens = makes up 2/3 of the eye

Question 10

What does the posterior segment contain?

Answer 10

Vitreous body = this contains the vitreous humour

Question 11

Where is a common site for floaters?

Answer 11

The vitreous body of the posterior segment

Question 12

What can raised intra-cranial pressure cause in the eye?

Answer 12

Ischaemia of the retina and glaucoma

Question 13

What makes up the ciliary body?

Answer 13

Smooth muscles and blood vessels

Question 14

What do ciliary processes secrete?

Answer 14

Secretes aqueous

Question 15

Where does aqueous circulate in the eye?

Answer 15

Circulates within posterior chamber = nourishes lens

Then passes through pupil into anterior chamber = nourishes cornea

Question 16

Where is aqueous reabsorbed?

Answer 16

Reabsorbed into scleral venous sinus (canal of Schlemm) at iridocorneal angle

Question 17

What is the iridocorneal angle often associated with?

Answer 17

It is the angle referred to in open or closed angle glaucoma

Question 18

What is an end artery?

Answer 18

An artery with insufficient anastomoses to maintain viability of the tissue supplied if arterial occlusion occurs

Question 19

What is the end artery of the retina?

Answer 19

The central artery of the retina

Question 20

What are the branches of the ophthalmic artery that supply the eye?

Answer 20

Ciliary artery and central artery of retina

Question 21

What branches does the ciliary artery give rise to?

Answer 21

Anterior and posterior ethmoidal arteries = supply nasal cavity and contribute to Kiesselbach’s plexus

Question 22

What is the only vein that drains the retina?

Answer 22

The central vein of the retina

Question 23

What is the fundus of the retina?

Answer 23

Posterior area where light is focused

Question 24

What structures are present within the fundus of the retina?

Answer 24

Optic disc, macula and fovea

Question 25

Where is the point of CN II formation?

Answer 25

The optic disc = only point of exit/entry for blood vessels and axons of CN II

Question 26

Why is the optic disc a blind spot in the eye?

Answer 26

It has no photoreceptors

Question 27

Which area of the retina has the greatest density of cones?

Answer 27

The macula

Question 28

Where is the fovea located within the retina?

Answer 28

In the centre of the macula = depression with 1.5mm diameter

Question 29

What is the area of the retina with the most acute vision?

Answer 29

The fovea

Question 30

Where do retinal veins and arteries lie?

Answer 30

Anterior to the retina

Question 31

What does complete interruption of retinal artery branches or the retinal vein cause?

Answer 31

Loss of an area of the visual field that corresponds to the area of ischaemia

Question 32

What does complete interruption to the central artery or vein of the retina cause?

Answer 32

Monocular blindness

Question 33

What is the relationship between axons of the visual pathway?

Answer 33

They maintain a specific spatial relationship from each other

Question 34

Where is light from objects in the right visual field processed?

Answer 34

By the left primary visual cortex

Question 35

Where is light from objects in the lower visual field processed?

Answer 35

By the upper part of the primary visual cortex

Question 36

What axes of the eye relate to the direction of gaze?

Answer 36

The vertical axis and the horizontal axis

Question 37

What area of the eye does the anteroposterior axis relate to?

Answer 37

The superior pole of the eyeball

Question 38

What are the movements related to each of the axes of the eye?

Answer 38

Vertical axis = abduction/adduction Horizontal axis = elevation/depression Anteroposterior axis = intorsion/extorsion (medial/lateral)

Question 39

What does each extra-ocular muscle have?

Answer 39

Each muscle will have a primary movement = most also have secondary movement (except medial and lateral rectus)

Question 40

Where do the movements of the extra-ocular muscles occur from?

Answer 40

The primary position (i.e gaze directed forwards)

Question 41

What angle of gaze is related to the superior and inferior rectus muscles?

Answer 41

23 degrees

Question 42

What angle of gaze is associated with the superior and inferior oblique muscles?

Answer 42

51 degrees

Question 43

What movement does the lateral rectus muscle perform?

Answer 43

Can only abduct eyeball = brings line of gaze into same plane as superior and inferior rectus muscles

Question 44

What nerve innervates the lateral rectus muscle?

Answer 44

CN VI

Question 45

What movement does the superior rectus muscles perform?

Answer 45

Elevation = only muscle that can elevate when eyeball is in abduction

Question 46

What movement does the inferior rectus muscle perform?

Answer 46

Depression = only muscle that can depress when eyeball is abducted

Question 47

What is the action of the medial rectus muscle?

Answer 47

Can only adduct eyeball = brings line of gaze into same plane as superior and inferior oblique muscles

Question 48

What extra-ocular muscles are innervated by CN III?

Answer 48

Superior and inferior rectus muscles, medial rectus muscle, inferior oblique muscle

Question 49

What is the action of the inferior oblique muscle?

Answer 49

Elevation = only muscle that can elevate when eyeball is adducted

Question 50

What movement does the superior oblique muscle perform?

Answer 50

Depression = only muscle that can depress when they eyeball is adducted

Question 51

What nerve innervates the superior oblique muscle?

Answer 51

CN IV

Question 52

What does movement of the eye normally require?

Answer 52

Action of more than one muscle = synergists, antagonists or both

Question 53

What muscles act together to perform pure elevation?

Answer 53

Superior rectus and inferior oblique synergistically work together (antagonists as rotators)

Question 54

What muscles act together to perform pure depression?

Answer 54

Superior oblique and inferior rectus synergistically work together (antagonists as abductors/adductors)