Orbit, Eye & Lacrimal Apparatus

Question 1

what bone is the superior part of the orbit?

Answer 1

frontal bone

Question 2

what bone lies inferomedially to the orbit?

Answer 2

maxilla

Question 3

what bone makes up the lateral margin of the orbit?

Answer 3

zygomatic bone

Question 4

what are the openings into the orbit?

Answer 4

• superior orbital fissure
• optic canal
• inferior orbital fissure
• nasolacrimal canal

Question 5

what nerves enter the orbit via the superior orbital fissure?

Answer 5

• frontal branch of CNV1
• lacrimal branch of CNV1
• trochlear nerve (CNIV)
• abducens nerve (VI)
• superior branch of occulomotor nerve (CNIII)
• inferior branch of occulomotor nerve (CNIII)
• nasocilliary branch of ophthalmic nerve CNV1

Question 6

what nerve enters the orbit via the optic canal?

Answer 6

optic nerve

Question 7

what runs within the optic nerve?

Answer 7

retinal artery & vein

Question 8

why is the retrobulbar fat present in the orbit?

Answer 8

to support the eyeball

Question 9

why can a pituitary tumour affect vision? what is the result?

Answer 9

the optic chiasm lies just superior & anterior to the pituitary gland
- tumour will press on the optic chiasm
- this causes visual field issues/tunnel vision

Question 10

what encases the optic nerve?

Answer 10

meninges and subarachnoid space extends from the skull along the optic nerve to the sclera

Question 11

what can cause swelling of the optic disc?

Answer 11

Papilloedema
- caused by raised intracranial pressure in the meninges & subarachnoid space around the optic nerve
- this slows retinal venous drainage

Question 12

what can cause painless temporary loss of vision?

Answer 12

occlusion of the central retinal artery

Question 13

what is Amaurosis Fugax?

Answer 13

temporary loss of vision

Question 14

what are the actions of the orbicularis oculi?

Answer 14

• close eyelids gently (involuntary, palpebral part)
• close eyelids tightly (voluntary, orbital part)

Question 15

what may occur as a result of malfunction of the orbicularis oculi muscle?

Answer 15

• sagging of lower eyelid
• leakage of tears
• dry eyes (with potential of corneal ulceration)

Question 16

where is the lacrimal gland located?

Answer 16

upper lateral corner of the orbit

Question 17

how are the eyes kept moist?

Answer 17

tears are secreted into the conjunctival sac & continually washed across the eye by blinking of the eyelids (orbicularis oculi)

Question 18

where do tears drain?

Answer 18

tears drain via puncta to canaliculi, to lacrimal sac, to nasolacrimal duct & to inferior nasal meatus

Question 19

what is the parasympathetic supply of the lacrimal gland?

Answer 19

1. preganglionic parasympathetic fibres travel from facial nerve via the greater petrosal nerve & then nerve of pterygoid canal
2. arrive in the pterygopalatine ganglion
3. postganglionic parasympathetic fibres hitch-hike via zygomatic branch of CNV2 to reach the lacrimal gland

Question 20

what 2 muscles lie on the superior aspect of the eye?

Answer 20

• superior rectus muscle
• levator palpebrae superioris

Question 21

what muscles are located on the sides of the eye?

Answer 21

• lateral rectus
• medial rectus
• inferior oblique
• superior oblique

Question 22

what are the extraocular muscles of the eyes?

Answer 22

• 4 recti
• 2 obliques

Question 23

what nerves supply the rectus muscles?

Answer 23

• superior rectus = CNIII
• medial rectus = CNIII
• inferior rectus = CNIII
• lateral rectus = CNVI

Question 24

what does the occulomotor nerve supply?

Answer 24

• extraocular muscles (except lateral rectus)
• levator palpebrae superioris

Question 25

what nerve carries parasympathetic fibres for pupil constriction & accomodation?

Answer 25

occulomotor nerve (CNIII)

Question 26

what occurs if the occulomotor nerve in injured?

Answer 26

• dilated pupil (mydriasis)
• upper eyelid drooping (ptosis)
• eye is turned downwards & outwards

Question 27

what is the innermost layer of the eye?

Answer 27

the retina

Question 28

what forms the outer fibrous layer of the eye?

Answer 28

sclera

Question 29

what lies between the outer sclera and the inner retina?

Answer 29

the vascular choroid layer

Question 30

what is Glaucoma?

Answer 30

damage to the optic nerve caused by fluid building up in front part of eye (increases pressure inside eye)
- can lead to vision loss