Anatomy of the Eye

Question 1

What is the bony orbit closely related to?

Answer 1

Air sinuses

Question 2

What of the orbit have thick walls?

Answer 2

Orbital rims and lateral and superior walls

Question 3

What does the thin walls of the rest of the orbit mean clinically?

Answer 3

Can be easily fractured leading to herniation into surrounding sinuses

Question 4

Why is the medial wall of the orbit weak?

Answer 4

Composed of the lamina papyracea of the ethmoidal bone

Question 5

What nerve can be effected when orbit herniates?

Answer 5

Maxillary nerve - sensory effects will be altered

Question 6

What is a classic sign of a blow out fracture on CT?

Answer 6

Teardrop sign

Question 7

What does orbital fat cushion?

Answer 7

The globe, very important for support

Question 8

What does hypertrophy of the fat lead to?

Answer 8

Orbital pushed outwards - can see more of the sclera

Question 9

How many layers does the cornea have?

Answer 9

5
Stratified squamous non-keratinising epithelium
Bowman's membrane
Stroma
Descemet's layer
Endothelium

Question 10

What is the structure of the stroma layer of cornea?

Answer 10

Regularly arranged collagen with no blood vessels

Question 11

Why are corneal transplants easier?

Answer 11

Cornea doesn’t have blood vessels and so the donor’s different antigens aren’t recognised as foreign

Question 12

What makes up the fibrous coat of the eyeball?

Answer 12

Cornea and sclera

Question 13

What makes up the vascular layer of the eyeball?

Answer 13

Ciliary body
Choroid
Iris
Retina

Question 14

What is the ciliary body?

Answer 14

Suspends the lens and produces aqueous humour

Question 15

what is the iris?

Answer 15

Controls diameter of pupil

Question 16

What is the choroid?

Answer 16

Supplies blood to outer layers of retina

Question 17

What makes up the sensory layer?

Answer 17

Retina

Question 18

What is the sclera?

Answer 18

Gives attachment to muscles moving eyeball

Question 19

What is the cornea?

Answer 19

Window to allow light rays to enter eyeball

Question 20

How many layers does the retina have?

Answer 20

10 layers

Question 21

What is layer 1 of the retina?

Answer 21

Pigment epithelial layer

Question 22

What is layer 2 of the retina?

Answer 22

Rods and cones - where light gets transducer into action potential

Question 23

What is layer 9 of the retina

Answer 23

Nerve fibre layer

Question 24

What forms the optic nerve?

Answer 24

Ganglion axons

Question 25

What is the optic disc?

Answer 25

Where all the nerves accumulate

Question 26

What are the blood vessels that radiate from the optic disc branches of?

Answer 26

Central retinal artery which is branch of opthalmic artery

Question 27

What is the fovea centralis?

Answer 27

Point in the retina where there is lots of cones and no rods | This is part of best visual acuity

Question 28

What is the lens?

Answer 28

Transparent, crystalline bioconvex structure which is suspended by zones from ciliary body

Question 29

What is needed for the lens to be transparent?

Answer 29

Needs to be avascular

Question 30

Where is the anterior segment of the eye?

Answer 30

In front of the lens | Also splits into anterior and posterior chambers either side of the iris

Question 31

What is aqueous humour?

Answer 31

Watery fluid anterior to the lens | Helps maintain intraocular pressure

Question 32

Where is the posterior segment of the eye?

Answer 32

Behind the lens

Question 33

What is the vitreous humor?

Answer 33

Transparent gel posterior to the lens, helps cushion the retina

Question 34

What produces Ah?

Answer 34

Ciliary body

Question 35

Where does the AH get filtered?

Answer 35

Angle of the anterior chamber

Question 36

What is AH filtered through?

Answer 36

Trabecular meshwork

Question 37

What leads to an increase in intraocular pressure?

Answer 37

Obstruction in the pathway of circulation of AH

Question 38

What does an increase in intraocular pressure cause?

Answer 38

Glaucoma

Question 39

What is the conjuctiva?

Answer 39

Thin vascular membrane that covers inner surface of eyelids and loops back over sclera

Question 40

Where is the lacrimal gland situated?

Answer 40

Laterally in the orbit

Question 41

What provides innervation to the lacrimal gland?

Answer 41

Parasympathetic innervation by facial nerve

Question 42

Where do the ducts of the lacrimal glands open into?

Answer 42

Conjunctival sac

Question 43

Where do tears drain?

Answer 43

Punctae on medial side of each eyelid and then into lacrimal sac Then through nasolacrimal duct into inferior meatus of nasal cavity

Question 44

What are the functions of the tear film?

Answer 44

Keeps cornea moist, prevents drying Washes away any particulate foreign bodies Has antibodies and lysozymes to kill microbes Smooths outer surface of cornea providing smooth surface for refraction

Question 45

What are the layers of the tear film?

Answer 45

Mucinous layer overlying corneal epithelium Aqueous layer (largest layer) Oily layer which is most superficial