The eyes in health and disease

Question 1

what type of epithelium lines the cornea?

Answer 1

stratified squamous non-keratinised epithelium

Question 2

what is the name of the basement membrane which the epithelium lies on?

Answer 2

bowman membrane

Question 3

where does the storm of the cornea gets its nutrition from and why?

Answer 3

the cornea contains no blood vessels

it gets it nutrition from the aqueous humour and surrounding blood vessels

Question 4

what type of fibre are found within the storm of the cornea?

Answer 4

regularly arranged collagen fibres

Question 5

what makes the cornea transparent?

Answer 5

collagen fibres are regularly arranged
no blood vessels
endothelial layer has a pump which actively keeps aqueous humour out of the cornea

Question 6

why does avasularity play an important role in corneal transplant?

Answer 6

because there are no blood vessels, there are no antigens
you don’t have to worry about antigen mismatch between donor and recipient
lesser chance of graft rejection

Question 7

regarding the drainage of the AH, where does it stop?

Answer 7

the angle of the anterior chamber

Question 8

describe the drainage of the AH?

Answer 8

produced in posterior chamber of anterior compartment
it is released from the ciliary body
it stops at the angle of the anterior junction
and flows out through the trabecular meshwork and then into shclemms canal
this then leads into venous circulation

Question 9

what is the histological structure of the retina?

Answer 9

10 layers ;
1st layer = pigment epithelium (nourishes rods and cones)
2nd layer = layer of rods and cones (photosensitive layer)
9th layer = fibrous layer

Question 10

what layer of the retina is the rods and cones found?

Answer 10

2nd layer (photosensitive layer)

Question 11

what type of blood vessels is the choroid made up of?

Answer 11

fenestrated blood vessels

Question 12

what is the blood supply of the retina?

Answer 12

10th layer supplied by the choroid

inner 9 layers supplied by the central retinal artery

Question 13

what is the main problem which causes age related macular degeneration of the retina?

Answer 13

dystrophy that affects the pigment epithelial layer (1st layer) of the retina which leads to destruction of the rods and cones
this is because the pigment epthelial layer nourishes the rods and cones

Question 14

what is the part of the eye which has the most acuity and why?

Answer 14

the fovea centralis

the part which is packed with the most rods and cones

Question 15

what is the structure of the lens?

Answer 15

transparent

biconvex

Question 16

what predisposes the lens to becoming opaque later on in life and what is this termed as?

Answer 16

the avascularity of the lens

this is known as cataract

Question 17

what is one of the main causes of the lens becoming opaque later on in life?

Answer 17

UV rays which the lens absorbs to protect the cornea from damage

Question 18

what muscle just lies underneath the surface of the eyelid and what action does it have? what nerve innervation does it have?

Answer 18

levator palpebrae superioris
elevates the eyelid
CN III

Question 19

what prevents evaporation of the eyes tear film?

Answer 19

meibomian glands found at the tarsal plate

Question 20

how long does it take before th tear film breaks up?

Answer 20

4 seconds

Question 21

how long does it take before there is ocular discomfort ?

Answer 21

5 seconds

Question 22

how long does it take before you take a blink?

Answer 22

7 seconds

Question 23

how does the tear film stimulate blinking?

Answer 23

when the eyes are open the aqueous components of the tears begin to evaporate
eventually the oily and mutinous layer will meet
when these 2 layers meet it causes the tear film to break up which stimulates blinking

Question 24

what is the nerve stimulation of secretion of tears into the conjunctival sac?

Answer 24

parasympathetic facial nerve CN VII

Question 25

what are the 3 layers of the tear film?

Answer 25

inner - mucinous layer
middle - aqueous layer
outer - oily layer

Question 26

what are the functions of the tear film?

Answer 26

keeps cornea moist and 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 27

what photoreceptor is responsible for colour vision?

Answer 27

cones

Question 28

how many different types of photoreceptor cones are there?

Answer 28

3

Question 29

how is colour vision assessed?

Answer 29

ishihara plates