Lecture 15- The Eye: Globe

Question 1

how many layers of the eyeball (globe)

Answer 1

3

Question 2

name the layers of the globe from outer to inner

Answer 2

Sclerea

Choroid

Retina

Question 3

the sclera

Answer 3

• outermost layer
• white part of eye- opaque
• most antieroly becomes transparent

Question 4

most anteriorly the sclera becomes transparent, what is this called

Answer 4

cornea

• transparent so we can see

Question 6

choroid

Answer 6

• middle layer
• huge olexus of blood vessels within this layer
• supplies the retina
• continous with ciliary body and iris

Question 7

ciliary body

Answer 7

includes muscle and ciliary processes

1. Important role e.g. muscle important in altering the thickness of the lens

Question 8

the iris

Answer 8

an anterior continuation of the choroid layer

• Coloured part of the eye
• Iris is a muscular diaphragm with a central aperture (opening in a lens through which light passes) – the pupil

Question 9

which muscles constrict and relax the aperture of the pupil

Answer 9

Sphincter papillae and dilator papillae (ANS) constrict and relaxed aperture of pupil

Question 10

inflammation of the choroid layer

Answer 10

uveitis

Question 11

Iritis

Answer 11

(anterior uveitis): painful ++ red eye and photosensitive

Question 12

retina

Answer 12

• innermost layer
• photosensitive layer- photoreceptors
• cells within the retina convery APs out the back of the eye via the optic nerve (optic canal) to the occipital lobe

Question 13

• Area of the retina lying lateral to the optic nerve called the

Answer 13

• macula

Question 14

macula

Answer 14

Area of the back of the eye which is responsible for our highest acuity vision –> colour vision

• High proportion of cones- detect colour- type of photoreceptor

Question 15

At the very tip of the macula- central depression called the

Answer 15

fovea

Thinnest part of the retina –> light doesn’t need to travel as far to photoreceptors (esp cones)

Question 16

cells which make up the rteina

Answer 16

pigment epithelial cells

photoreceptors

ganglion cells

Question 17

pigment epithelial cells

Answer 17

• Outer most layer (brown coloured)= pigment epithelial cells- closest to choroid layer
  
  • Do not generate APs but help absorb excess light- prevent scattering of light

Question 18

• Photoreceptors

Answer 18

Rods and cones–> convey APs to retinal ganglion cell

Question 19

• ganglion cell

Answer 19

innermost cell

Ganglion cells converge as the optic nerve

Question 20

chambers of the eye

Answer 20

antirior and posterior right at the front of the eye

Question 21

Anterior chamber

Answer 21

• Space between cornea and iris

Question 22

Posterior chamber

Answer 22

• Space between iris and the lens
• Ciliary processes produce aqueous humour
• Circulates through posterior and passes through the pupil into the anterior chamber
• Bathes cornea and lens with nutrients and oxygen (avascular)

Question 23

Vitreous body

Answer 23

• Filled with vitreous humour (firm, clear gel-like fluid)
• Fills large portion of globe of eye
• Pushes up against retina but not stuck to it

Question 24

most of the anterior surface of the eyeball is covered in conjunctival memebrane (reflecting the inner surface of eye lid)… however which part of the anterior surface is not covered

Answer 24

cornea (opaque part of the sclera)

Question 25

features of the conjunctiva

Answer 25

• Can be seen when eye infected or inflamed e.g.
  
  • Conjunctivitis and
  • Subconjunctival haemorrhage

Question 26

• Conjunctivitis – usually viral

Answer 26

• Causes red eye
• But eye not painful
• Highly contagious

Question 27

• Subconjunctival haemorrhage

Answer 27

• When tiny blood vessel in conjunctiva bursts
• Can look shocking
• But completely self- limiting
• No pain

Question 28

decribe blood supply to the eyeball

Answer 28

• Branches of the ophthalmic artery (first branch of internal carotid) supplies eye structures
  
  • Central retinal artery (branch of ophthalmic) supplies the retina
    
    • But also draws supply from underlying choroid layer
  • Ciliary arteries (posterior and anterior feed extensive capillary bed within choroid layer)

Question 29

Central retinal artery occlusion

Answer 29

• Ciliary arteries undisturbed still good perfusion of choroid layer
• Distal branches of the central retinal artery that arise and supply the retina are starved of blood
  
  • Therefore in central retinal artery occlusion the retina looks very pale
  • Cherry red spot
    
    • Obvious in area of macula
      
      • Arises because macula and fovea are thinnest part of the retina- can see underlying choroid much more clearly than usual contrast is much more obvious when rest of the retina is very pale due to loss of blood supply, but still very well perfused choric layer