The eye and visual system 17.02.23

Question 1

what is a corneal reflex?

Answer 1

Eye can sense something on its surface so we blink

Question 2

what are the 3 layers of the eye?

Answer 2

• Outer layer (sclera and cornea)
• Middle layer (Uvea)
• Inner layer (retina)

Question 3

What is the structure of the sclera?

Answer 3

tough fibrous outer coat, made up of collagen in a pattern

Question 4

What is the function of the sclera?

Answer 4

• Transparent for light transmission
• Tough because it is a barrier to trauma and infection
• it is responsible for 2/3 of the refractive power of the eye

Question 5

What is the function of the cornea?

Answer 5

• Transmission of light
• Refraction

Question 6

What is the structure of the cornea?

Answer 6

• Transparent (opaque indicated cataracts)
• Smooth spherical surface
• Corneal clarity is maintained by pumping water out
• Surface epithelium can be repaired

Question 7

What are the 5 layers of the cornea?

Answer 7

Epithelium (can regenerate)
Bowman’s Layer
Stroma
Descemet’s layer
Endothelium (can’t regenerate)

Question 8

What three structures make up the middle layer of the eye?

Answer 8

• Iris (extension of the choroid)
• Ciliary body (specialised layer of muscle cells)
• Choroid

Question 9

What is the function of the choroid?

Answer 9

It is the blood supply to the outer third of the retina and provide oxygen and nourishment to the outer retina
- Highly pigmented

Question 10

What is the function of the iris?

Answer 10

• The coloured part of the eye
• Contains dilator (make pupil larger: sympathetic)
• and sphincter pupillae muscles (makes pupils smaller: parasympathetic)
• and controls pupillary reflexes

Question 11

what is the function of the ciliary body?

Answer 11

• It has a specialised epithelial lining of glandular epithelium
• This produces aqueous humour
• The ciliary (smooth) muscle controls accommodation (focusing)
• Maintains pressure in eye

Question 12

What is the function of the retina?

Answer 12

• Contains specialised cells: photoreceptors
• Organ of photo transduction
• Produces vitreous humour (helps maintain pressure)

Question 13

What is the macula lutea?

Answer 13

this is responsible for detailed central vision of the retina and it contains the fovea centralis which is the centre of the macula.
- If this gets damaged, vision is severely impaired

Question 14

What do cones and rods do?

Answer 14

Cones: see colour and high resolution
Rods: Black and white and low resolution

Question 15

What cells support the activation of the photo receptor cell?

Answer 15

When light enters the eye it stimulates the photoreceptor cells with the help of:
- Bipolar cells
- Amacrine and horizontal cells
- Muller glial cells
Then the retinal ganglion cells of a neuron receive this information from the photoreceptors

Question 16

What humour is in the anterior segment?

Answer 16

Aqueous humour
- Which is the nutrition to the lens and cornea
- And maintains intraocular pressure

Question 17

What is the function of the lens?

Answer 17

• Biconvex
• responsible for 1/3 refractive power of the eye
• accomodation

Question 18

What is emmetropia?

Answer 18

6/6 vision

Question 19

What is Hypertropia?

Answer 19

• Underpowered to focus near objects on retina
• far sighted
• Will receive a + lens

Question 20

What is Myopia?

Answer 20

• Overpowered so can’t focus far objects on retina
• Near sighted
• Will receive a - lens

Question 21

What humour is in the posterior segment?

Answer 21

• Vitreous humour
• This is a avascular viscoestalic gel
• Contains Hyaluronic acid and collagen

Question 22

What adnexae help support the eye?

Answer 22

• Eyelids
• Conjunctiva
• tear film

Question 23

what are the three layers of the tear film?

Answer 23

• Anterior: Lipid
• Middle: aqueous
• Posterior: Mucous

Question 24

What is the function of the lipid layers of the tear film and how is it made?

Answer 24

function: Prevents evaporation
Made by: Meibomian gland and Zeis

Question 25

What is the function of the aqueous layers of the tear film and how is it made?

Answer 25

Function is for fluidity and nutrition and prevents infection
Made by the lacrimal and accessory lacrimal glands

Question 26

What is the function of the mucosal layers of the tear film and how is it made?

Answer 26

Lubricates and aids even distribution of tears
Made by the conjunctival goblet cells

Question 27

What is the arterial supply to the inner retina?

Answer 27

Internal carotid artery:
- into the ophthalmic artery, central retinal artery and ciliary arteries
External Carotid artery:
- Facial artery supplies the medial lid and orbit

Question 28

How is the eye drained (which veins)?

Answer 28

• drained by branch retinal veins
• central retinal v.
• ophthalmic v.
• cavernous sinus
• Internal jugular v.

Question 29

What is the blood supply to the outer retina?

Answer 29

Outer 1/3 by the choroid
- posterior ciliary artery

Question 30

How is the choroid drained?

Answer 30

By vortex veins, usually one for each quadrant

Question 31

What parts of the eye have lymphatics drainage?

Answer 31

Conjunctiva and lids do have lymphatic drainage to submandibular nodes

Question 32

What is the structure of the cornea?

Answer 32

• Transparent (opaque indicated cataracts)
• Smooth spherical surface
• Corneal clarity is maintained by pumping water out
• Surface epithelium can be repaired