Eyeball & Visual Pathways

Question 1

Answer 1

Question 2

What are the boundaries of the orbit?

Answer 2

Superior = Anterior cranial fossa
Inferior = Maxillary paranasal sinuses

Inferomedially = Nasal cavity

Posteriorly = Middle cranial fossa

Laterally - maxilla (zygomatic process) and zygomatic bone

Question 3

How many bones comprise the bony orbit?

Answer 3

7

Question 4

Which bones comprise the roof of the orbit?

Answer 4

Frontal bone (orbital part)

Sphenoid bone (lesser wing)

Question 5

Which bones comprise the medial wall of the orbit?

Answer 5

Maxilla bone (frontal process)

Lacrimal bone

Ethmoid bone

Sphenoid bone

Question 6

Which foramina are found in the roof of the orbit?

Answer 6

Trochlear fovea

Lacrimal fossa (for lacrimal duct)

Question 7

Which foramina are found in the medial wall of the orbit?

Answer 7

Anterior & posterior ethmoidal foramina (ethmoidal vessels & nerves)

Optic canal (optic nerve & ophthalmic artery)

Question 8

What runs through the optic canal?

Answer 8

Optic nerve & ophthalmic artery

Question 9

Where does the opthalmic artery arise from?

Answer 9

The internal carotid

Question 10

Which bones make up the floor of the orbit?

Answer 10

Maxilla (orbital surface)
Zygomatic bone
Palatine bone

Question 11

Which bones make up the lateral wall of the orbit?

Answer 11

Zygomatic bone
Sphenoid bone (greater wing)

Question 12

Which foramina are found in the floor of the orbit?

Answer 12

Inferior orbital fissure

Question 13

What runs through the inferior orbital fissure?

Answer 13

V2 (maxillary division)
Infra-orbital vessels
Inferior ophthalmic vein

Question 14

Which foramina are found in the lateral wall of the orbit?

Answer 14

Superior orbital fisure

Question 15

What runs through the superior orbital fissure?

Answer 15

CN III, IV, V (1), VI

V(1) = lacrimal, frontal & nasociliary branches

Also - superior ophthalmic vein

Question 16

What is the difference between a fissure and a foramen?

Answer 16

Fissures are longer

Question 17

Which are the main vessels of the orbit?

Answer 17

Ophthalmic artery
Superior ophthalmic vein
Inferior ophthalmic vein

Question 18

What is an important risk factor about the ophthalmic veins?

Answer 18

Ophthalmic veins communicate with the venous drainage of the face, the pterygoid plexus and pass posteriorly draining into the cavernous sinus.

This is an infection transmission risk!

Question 19

Answer 19

Question 20

Which nerves innervate the orbit?

Answer 20

CN II (Optic)
III (Occulomotor) - divides into superior and inferior
Trochlear (IV)
Abducens (VI)

V1 - Ophthalmic division -> nasociliary nerve, lacrimal nerve & frontal nerve

Question 21

Is the optic nerve afferent or efferent? Where does it arise from?

Answer 21

Arises from the retina - carries afferent information

Question 22

Answer 22

Question 23

What does the oculomotor nerve do?

Answer 23

Carries motor efferent signals to the extrinsic orbital muscles &
PSS innervation to intrinsic muscles of the eye (via ciliary ganglion)

Question 24

What does the trochlear nerve do in the orbit?

Answer 24

Carries motor efferent signals to the superior oblique muscle.

Question 25

What does the abducens nerve do in the orbit?

Answer 25

Carries motor efferent signals to the lateral rectus muscle.

Question 26

What are the four PSS ganglia in the head and neck associated with cranial nerves?

Answer 26

Ciliary Otic Submandibular Pterygopalatine

Question 27

Which ganglion is involved with the parasympathetic innervation of the eye?

Answer 27

Ciliary ganglion

Question 28

What is the pathway for the autonomic innervation of the orbit?

Answer 28

Edinger-Westphal nucleus in midbrain -> Occulomotor nerve (III) -> Ciliary ganglion -> Short ciliary nerves

Question 29

What does the autonomic nervous system control in the eye?

Answer 29

SS = dilation of pupil PSS = constriction of pupil

Question 30

What surrounds the outside of the eyeball (but does not extend over the cornea)?

Answer 30

Fascial sheath

Question 31

What passes through the fascial sheath to enter the sclera?

Answer 31

Extra-ocular muscles

Question 32

What dos the inferior thickening of the fascial sheath become?

Answer 32

The suspensory ligament

Question 33

What fixes the eyeball in orbit and limits movement from the medial and lateral rectify muscles?

Answer 33

Check ligaments (medial and lateral)

Question 34

What are the check ligaments formed from?

Answer 34

Continuation of fascia from the lateral and medial recti muscles

Question 35

What are the layers of the eye?

Answer 35

External fibrous layer Middle vascular layer Inner neural layer

Question 36

What does the external fibrous layer of the eye comprise of?

Answer 36

Sclera and cornea

Question 37

What is the sclera made of? What does it do?

Answer 37

Made of dense connective tissue (white). Is attachment for the external orbital muscles.

Question 38

What does the middle vascular layer of the eye comprise of?

Answer 38

Choroid Ciliary body Iris

Question 39

What is the ciliary body made up of?

Answer 39

Ciliary muscle Ciliary processes Zonular fibres

Question 40

What is the retinal divided into?

Answer 40

Pigmented layer (external) Neural layer (internal)

Question 41

What does the pigmented layer of the retina do?

Answer 41

Absorbs excess light and prevents reflections of light

Question 42

What does the neural layer of the retina do?

Answer 42

Is the neurologically functional layer of the eye that contains photoreceptors which generate an image

Question 43

What is the name of the place on the retina where the axons come together to form the optic disc?

Answer 43

Blind spot

Question 44

Where is the fovea centralis found?

Answer 44

Middle of the macula lutea

Question 45

What is the macula lutea?

Answer 45

A yellow spot on the retina that allows light to focus when looking at an object

Question 46

What does the fovea centralis do?

Answer 46

It is a structure in the centre of the macula lutea that contains a high density of cone photoreceptors & allows the light to focus within the eye.

Question 47

The front part of the eye is divided into what?

Answer 47

Anterior segment Lens Posterior segment

Question 48

What is the anterior segment of the eye formed of?

Answer 48

Anterior chamber Iris & pupil Posterior chamber §

Question 49

Answer 49

Question 50

Which part of the eye contains the aqueous humour?

Answer 50

The anterior segment

Question 51

What are the two axes of the eye?

Answer 51

Axis of orbit Axis of eyeball

Question 52

What is the function of the extrinsic muscles of the eye?

Answer 52

Move the eyeball Move the eyelid

Question 53

What are the extrinsic muscles of the eye?

Answer 53

Superior rectus Inferior rectus Medial rectus Lateral rectus Superior oblique Inferior oblique Levator palpeerde superioris

Question 54

Answer 54

Question 55

Answer 55

Question 56

Which muscle passes through the trochlear nerve?

Answer 56

Superior oblique

Question 57

Which extrinsic muscles insert more anteriorly and which extrinsic muscles insert more posteriorly on the eye?

Answer 57

Rectus muscles = more anteriorly Obliques = more posteriorly

Question 58

Answer 58

Question 59

Answer 59

Question 60

Which nerve innervates the superior oblique muscle?

Answer 60

SO4 = Trochlear nerve

Question 61

Which nerve innervates the lacteral rectus muscle?

Answer 61

LR6 = Abducens nerve

Question 62

Which nerve innervates the inferior oblique and medial, superior and inferior rectus muscles?

Answer 62

CN III (Oculomotor)

Question 63

What is the function of the intrinsic muscles of the eye?

Answer 63

Control - Size of pupil - Shape of the lens

Question 64

What are the intrinsic muscles of the eye? Which part of the autonomic system do they carry information from?

Answer 64

Ciliary muscles - from PSS Sphincter pupillae - from PSS Dilater pupillae - from SS

Question 65

Answer 65

Question 66

What does the lacrimal apparatus comprise of?

Answer 66

Lacrimal - gland - canaliculi - sac & Nasolacrimal duct

Question 67

Answer 67

Question 68

What opens into the lacrimal canaliculi?

Answer 68

Lacrimal puncta

Question 69

What is the function of the lacrimal apparatus?

Answer 69

Production, maintenance and drainage of the lacrimal fluid from the external surface of the eyeball.

Question 70

What type of gland is the lacrimal gland?

Answer 70

Exocrine

Question 71

Where is the lacrimal gland found?

Answer 71

In the lacrimal fossa in the four of the orbit

Question 72

What is the lacrimal gland divided into and by what?

Answer 72

Orbital and palpebral parts Divided by the elevator palpebrae superioris

Question 73

Which vessels supplies the lacrimal gland?

Answer 73

Ophthalmic artery (via ICA)

Question 74

Which nerve innervates the lacrimal gland?

Answer 74

The Ophthalmic division of the Trigeminal V (1)

Question 75

What are the three neural cell types in the neural layer?

Answer 75

Ganglion cells Bipolar cells Photoreceptors (rods and cones)

Question 76

What are rods and cones sensitive to?

Answer 76

Rods - dim light sensitive Cones - bright light and colour sensitive

Question 77

What do the myelinated axons of the ganglion cells form? Where do they exit the eyeball?

Answer 77

Optic nerve - exit at the optic disc.

Question 78

Where does the optic nerve exit the eyeball?

Answer 78

Optic disc

Question 79

Answer 79

Question 80

What is the order of the visual pathway

Answer 80

Light enters the eye - stimulates - Photoreceptors --> Bipolar cells --> Ganglionic cells ---> Optic nerve Optic nerve --> Optic chasm --> Optic tracts --> Lateral geniculate nucleus --> Optic radiations --> Primary visual cortex (17)

Question 81

Which brodmann area is the primary visual cortex?

Answer 81

17

Question 82

Answer 82

Question 83

Answer 83

A - right frontal lobe B - left globe / eyeball C - optic nerve D - right medial rectus muscle (superior oblique directly above) E - tongue Bright signal = fat - therefore T1 (fluid dark)

Question 84

What does thyroid disease do to the eye?

Answer 84

Enlarges the interocular muscles bilaterally (esp medial, inferior and superior rectus) - causes bulging eyes - most common in Graves disease

Question 85

Answer 85

Question 86

Answer 86