Lens and fundus

Question 1

Where does the lens sit?

Answer 1

Behind iris at anterior

Attached to vitreous at posterior

Question 2

What suspends the lens?

Answer 2

Zonular fibres from ciliary processes

Question 3

What is the purpose of the lens?

Answer 3

Focus light on the retina

Question 4

What is the lens reliant on?

Answer 4

Transparency
Stable position
Ability to change shape

Question 5

What does the lens consist of (4 parts)

Answer 5

Acellular capsule
Cortex of lens fibres
Central nucelus
Anterior epithelium

Question 6

What creates transparency in the lens?

Answer 6

Arrangement of lens fibres in the cortex

Question 7

What can be found where lens fibres meet? When are they more apparent?

Answer 7

Y-shaped suture lines

In cataracts

Question 8

What is a cataract? What causes it?

Answer 8

Cloudy lens

Disruption of lens fibres (in cortex)

Question 9

What is the function of the anterior epithelium of the lens?

Answer 9

Maintains hydration

Produces lens fibres

Question 10

The lens is avascular. How does it obtain nutrients and get rid of waste?

Answer 10

Via aqueous humour

Change in aqueous humour = change in lens

Question 11

What is the fundus of the eye?

Answer 11

Part of the posterior segment viewed with an opthalmasocpe

Question 12

What structures of the fundus are visible?

Answer 12

Optic disc
Retina
Retinal pigmented epithelium
Choroid

Question 13

Light must pass through several layers of the retina before reaching rods and cones. What assists with transparency?

Answer 13

Unmyelinated axons

Question 14

What are the layers of the retina?

Answer 14

Retina pigmented epithelium (outermost)

Axons of ganglia innermost

Question 15

Retinal blood vessels supply the inner retinal layers. What are these layers?

Answer 15

Nerve fibre layer
Ganglion cell layer
Inner plexiform layer

Question 16

Where do axons become myelinated in the retina?

Answer 16

At optic disc

Question 17

What is the name of the area with most cone cells? Where is it near?

Answer 17

Area centralis

Near optic disc

Question 18

What is the area of the retina with most ganglion cells? Where is it?

Answer 18

Visual streak

Same place as area centralis

Question 19

What is the function of the retinal pigmented epithelium

Answer 19

Phagocytose old photoreceptors
Vitamin A metabolism
Move metabolites in and out of retina

Question 20

What is the optic disc between in a dog?

Answer 20

Tapetal and non-tapetal fundus

Question 21

Where is the optic disc in the cat?

Answer 21

Within the tapetal dundus

Question 22

Where is the optic disc in large animals?

Answer 22

Within the non-tapetal fundus

Question 23

Is the optic disk light or dark? Which species is the exception?

Answer 23

Light

Cats - dark pink due to no myelin

Question 24

What is the difference of the blood supply of the neuroretina in cats and dogs?

Answer 24

Dogs more tortuous

Cats straighter

Question 25

How can arteries and veins be distinugished in the neuroretina? Which species is it difficult to see retinal vessels?

Answer 25

Arteries narrower than veins

Horse

Question 26

What do birds lack in their fundus?

Answer 26

No pigment
No tapetum lucid
No retinal blood vessels

Question 27

What do birds have additionally in their fundus? What is this? What does it do?

Answer 27

Pecten
Projection of choroid into posterior chamber
Helps diffusion of nutrients to retinal cells