Anatomy

Question 1

What are the orbital margins of the eye?

Answer 1

1. Supraorbital margin
   - frontal bone and its superior orbital notch
2. Medial margin
   - lacrimal bone
   - frontal process of maxillary bone
3. Infraorbital margin
   - zygomatic bone
   - maxillary bone
4. Lateral margin
   - frontal process of zygomatic bone

Question 2

What are the communications associated with the orbit?

Answer 2

1. Optic Canal (to middle cranial fossa)
   - optic nerve with its meningeal sheath
   - opthalmic artery
2. Superior orbital fissure (to middle cranial fossa)
   - 3rd, 4th, 5ath, 6th nerves
   - opthalmic veins
3. Inferior orbital fissure (to pterygopalatine and infratemporal fossa)
   - infraorbital (VAN)
   - zygomatic (VAN)
   - orbital rami of pterygopalatine ganglion
   -

Question 3

What are the layers of the eyeball?

Answer 3

1. Fibrous “outer” layer
   - sclera
   - cornea
2. Muscular, vascular “middle” layer
   i. cilliary bodies (muscle)
   - outer radial muscle (contraction cause thickening of the lens, vice versa)
   - inner circular muscle
   - secretes aqueous humour

ii. iris (muscle)
- inner, circular. sphincter papillae (parasymphatetic innervation)
- outer radial. dilator papillae (symphatetic innervation)

iii. choroids plexus (muscle + vascular)

3. Retina
   - optic part (neural, pigmented)
   - non optic (irideal, cilliary part, supplied by central retinal art.)

Question 4

What are the eyelids made of (outward-inwardly)?

Answer 4

1. Skin, subcutaneous tissue
2. Orbicularis oris
3. Tarsal plate (collagenous) containing meibomian glands, attached to levator muscle via aponeurosis
4. Palpebral conjunctiva

• orbicularis oris - 7th nerve - forced eye closure
• levator muscle - 3rd nerve - blink - damage cause ptosis
• smooth muscle (on levator surface) - symphatetic nerve - damage cause ptosis
• meiobomian glands - oil (lipid layer) to retard evaporation

Question 5

What are the components of lacrimal drainage apparatus?

Answer 5

Lacrimal gland (lacrimal fossa at greater wing of spehnoid bone -> upper and lower puncta -> upper and lower canaliculi -> common canaliculus -> lacrimal sac (between lacrimal crest) -> nasolacrimal duct -> lacrimal fold (inferior nasal meatus, below inferior conchae)

Question 6

What are the components and function of tear film?

Answer 6

Components:

1. mucin layer - golbet cells of conjunctiva
2. aqueous layer - lacrimal gland
3. surface oil layer - meiobomian gland

Function:

1. O2 to avascular cornea
2. Remove debris on ocular surface
3. Smooth interface to avoid distortion of refraction of light
4. Antibacterial properties

Question 7

What is anterior segment of the eye made of?

Answer 7

It the anterior 1/3 of the eye comprises structures in front of vitreous humour:

1. lens
2. ciliary bodies
3. iris
4. cornea
5. aqueous humour (including anterior and posterior chamber)
6. conjunctiva

Question 8

What is the posterior segment of the eye made of?

Answer 8

It is the posterior 2/3rd of the eye comprises anterior hyaloid membrane (ant vitreous membrane) and all the structures behind it.

1. vitreous humour
2. retina
3. choroid
4. optic nerve
5. retinal blood vessels

Question 9

What are anatomical components of the lens?

Answer 9

1. Outermost (capsule)~collagenous
2. Middle (cortex)
3. Innermost (nucleus)

• it has flat anterior, more convex posterior
• anterior part has a monolayer epithelium lining
• it grows throughout life

Question 10

Describes the ocular blood supply

Answer 10

Internal carotid artery -> opthalmic artery ->

i. retinal artery (retina) *except fovea ‘from choroid’
- endothelial cells form the inner-blood-retinal barrier
- retinal pigment epithelial cells form the external-blood retinal-barrier
ii. posterior cilliary arteries (choroid, anterior optic nerve)
- leaky, fenestrated
iii. muscular arteries (extraocular muscles)
iv. anastomosis between post. ciliary and muscular forms te anterior cilliary artery (iris, cilliary bodies)

Question 11

Corneal layers?

Answer 11

1. Epithelium
2. Basal membrane
3. Bowman’s membrane
4. Stroma (thickest)
5. Decemet’s membrane (regenerative potential)
6. Endothelium