0.1.2 basic eye anatomy

Question 1

what does the cornea form?

Answer 1

dome of the front of the eye

Question 2

what can you see through the cornea?

Answer 2

iris and pupil

Question 3

what is the pupil?

Answer 3

hole in centre of eye that allows light to pass into eye

Question 4

describe the cornea

Answer 4

• transparent
• refractive surface
• continuous with sclera
• covered with tear film
• no blood vessels as it need to be transparent

Question 5

layers of cornea (starting from superficial to deep, e.g from front of eye to back)

Answer 5

1. epithelium
2. Bowman’s layer
3. stroma
4. Descemet’s membrane
5. endothelium (faces aqueous in anterior chamber)

Question 6

describe endothelium of cornea

Answer 6

1. faces aqueous in anterior chamber
2. one cell thick which plays important role in maintaining corneal transparency

Question 7

what do cornea and sclera together form?

Answer 7

outer protective layer of eyeball

Question 8

how are cornea and sclera continuous?

Answer 8

• cornea forms 1/6th of the outer layer of eye (anterior 1/6th: transparent)
• sclera forms 5/6th of the outer layer : opaque bit

Question 9

junction between cornea and sclera?

Answer 9

limbus, where cornea loses transparency

Question 10

can we see the sclera?

Answer 10

we can see the anterior part of the sclera which lies under the conjunctiva

Question 11

describe the eyelids and eyelashes

Answer 11

• protective barrier
• keep eye surface lubricated (spread the teat film across)
• continuous blinking of eyelids prevents rapid evaporation of tear film
• Meibomian glands are modified sweat glands that produce oily component of tears
• tears drain through puncta (one at medial upper and lower eyelid)

Question 12

canthus

Answer 12

junction of upper and lower eyelid

Question 13

lateral canthus

Answer 13

• closest to ear

Question 14

medial canthus

Answer 14

• closest to nose
• medial caruncle: modified skin
• plica semilunari: stretches when eye moves allowing full lateral movement of eye

Question 15

what is the conjunctiva?

Answer 15

• clear membrane covering the sclera and eyelids (so contact lenses can’t go behind eye)
• protects eye
• supplies cornea with nutrients
• contains cells that secrete mucus

Question 16

bulbar conjunctiva

Answer 16

conjunctive that overlies the sclera

Question 17

tarsal conjunctiva

Answer 17

overlies the eyelids

Question 18

limbal conjunctiva

Answer 18

contains stem cells which can replace damaged corneal cells

Question 19

3 ocular spaces

Answer 19

1. anterior chamber
2. posterior chamber
3. vitreous chamber

Question 20

anterior chamber

Answer 20

• between cornea and iris
• contains aqueous

Question 21

posterior chamber

Answer 21

• between the iris and ciliary body
• contains aqueous

Question 22

vitreous chamber

Answer 22

• between posterior lens and retina
• contains vitreous

Question 23

what is the aqueous humour produced by?

Answer 23

clear liquid in anterior chamber produced by ciliary body

Question 24

what does the aq humour provide?

Answer 24

nutrients to posterior cornea and lens

Question 25

what does the aqueous humour drain out through?

Answer 25

structures in the anterior chamber angle

Question 26

the uveal tract

Answer 26

- iris, ciliary body, choroid - middle layer of eye - aka vascular pigmented layer/ middle tunic of eyeball - choroid is between retina and sclera, dense blood supply

Question 27

iris

Answer 27

- coloured part - contains muscles that control pupil size - amount of pigment determines eye colour - acts like a pupil stop in camera

Question 28

2 muscles in iris that control pupil size

Answer 28

1. iris sphincter: bright light 2. iris dilater: dim light

Question 29

what is behind the iris?

Answer 29

lens and zonules

Question 30

lens and zonules

Answer 30

- transparent lens provides focusing for eye - sits behind the iris suspended by zonular fibres - zonular fibres are attached to ciliary processes of ciliary body - changes in lens shape (accommodation) allows clear vision at different distances - with age, lens can become cloudy = cataract

Question 31

what does the lens provide for the eye?

Answer 31

focusing

Question 32

what does the lens sit behind?

Answer 32

the iris suspended by zonular fibres

Question 33

what are zonular fibres attached to?

Answer 33

ciliary processes of ciliary body

Question 34

what does accommodation allow?

Answer 34

changes in lens shape allow clear vision at different distances

Question 35

with age what happens to the lens?

Answer 35

can become cloudy = cataract

Question 36

what is within the ciliary body?

Answer 36

ciliary muscle which controls accommodation by contracting and releasing tension on the zonules

Question 37

ciliary processes

Answer 37

- part of the ciliary body - produce aqueous - site of attachment for the zonules

Question 38

does the lens continue to grow throughout life?

Answer 38

yes, it lays down more lens fibres

Question 39

accommodation & presbyopia

Answer 39

- process of changing the focus from distance to near is accommodation - as you age lens becomes fatter + more rigid, so you lose ability to accommodate, so we need reading glasses - this process is presbyopia = lens can no longer change shape, starts at 45

Question 40

what is the vitreous?

Answer 40

gel filling posterior chamber of eye

Question 41

what does the vitreous do?

Answer 41

provides shoe and rigidity to eye

Question 42

what happens to vitreous with age?

Answer 42

shrinks and liquifies (vitreous contains collagen)

Question 43

what does vitreous often contain?

Answer 43

- floaters - common in myopes and older patients

Question 44

what is the retina?

Answer 44

light sensitive tissue at back of eye

Question 45

what does the retina contain?

Answer 45

- photoreceptors absorb light and transmit nerve impulses to brain via optic nerve - rods and cones

Question 46

inner retina

Answer 46

retina closest to vitreous

Question 47

outer retina

Answer 47

retina that is closest to choroid

Question 48

what do rods function best in?

Answer 48

in poor light conditions

Question 49

what do cones function best it?

Answer 49

bright light

Question 50

optic nerve

Answer 50

- light signal exits eye at optic nerve - blind spot (bc theres no retina) - carried by axons of rentinal ganglion cells - head of optic nerve is optic disc

Question 51

what is the dark bit in the middle of a photo of the retina?

Answer 51

fovea

Question 52

fovea

Answer 52

- thinnest, most sensitive part of retina - provides central vision and optimal visual acuity - thinnest area of retina, other layers swept aside so light hits photoreceptors directly

Question 53

macula

Answer 53

- central area of fetina - its like the wider area around the fovea

Question 54

choroid

Answer 54

- lots of blood vessels to supply nutrients to retina - heavily pigmented, black in colour - absorbs light, preventing internal reflection of light

Question 55

sclera

Answer 55

- protective tough layer - provides rigidity to eye - continuous with cornea - opaque

Question 56

the orbit

Answer 56

- 6 extra ocular muscles which control eye movements - nerves

Question 57

abduction

Answer 57

eye moves away from midline

Question 58

adduction

Answer 58

eye moves towards midline (towards nose)

Question 59

elevation

Answer 59

looking upwards

Question 60

depression

Answer 60

looking downwards