Orbit, Eye & Lacrimal Apparatus Flashcards
what bone is the superior part of the orbit?
frontal bone
what bone lies inferomedially to the orbit?
maxilla
what bone makes up the lateral margin of the orbit?
zygomatic bone
what are the openings into the orbit?
- superior orbital fissure
- optic canal
- inferior orbital fissure
- nasolacrimal canal
what nerves enter the orbit via the superior orbital fissure?
- 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
what nerve enters the orbit via the optic canal?
optic nerve
what runs within the optic nerve?
retinal artery & vein
why is the retrobulbar fat present in the orbit?
to support the eyeball
why can a pituitary tumour affect vision? what is the result?
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
what encases the optic nerve?
meninges and subarachnoid space extends from the skull along the optic nerve to the sclera
what can cause swelling of the optic disc?
Papilloedema
- caused by raised intracranial pressure in the meninges & subarachnoid space around the optic nerve
- this slows retinal venous drainage
what can cause painless temporary loss of vision?
occlusion of the central retinal artery
what is Amaurosis Fugax?
temporary loss of vision
what are the actions of the orbicularis oculi?
- close eyelids gently (involuntary, palpebral part)
- close eyelids tightly (voluntary, orbital part)
what may occur as a result of malfunction of the orbicularis oculi muscle?
- sagging of lower eyelid
- leakage of tears
- dry eyes (with potential of corneal ulceration)
where is the lacrimal gland located?
upper lateral corner of the orbit
how are the eyes kept moist?
tears are secreted into the conjunctival sac & continually washed across the eye by blinking of the eyelids (orbicularis oculi)
where do tears drain?
tears drain via puncta to canaliculi, to lacrimal sac, to nasolacrimal duct & to inferior nasal meatus
what is the parasympathetic supply of the lacrimal gland?
- preganglionic parasympathetic fibres travel from facial nerve via the greater petrosal nerve & then nerve of pterygoid canal
- arrive in the pterygopalatine ganglion
- postganglionic parasympathetic fibres hitch-hike via zygomatic branch of CNV2 to reach the lacrimal gland
what 2 muscles lie on the superior aspect of the eye?
- superior rectus muscle
- levator palpebrae superioris
what muscles are located on the sides of the eye?
- lateral rectus
- medial rectus
- inferior oblique
- superior oblique
what are the extraocular muscles of the eyes?
- 4 recti
- 2 obliques
what nerves supply the rectus muscles?
- superior rectus = CNIII
- medial rectus = CNIII
- inferior rectus = CNIII
- lateral rectus = CNVI
what does the occulomotor nerve supply?
- extraocular muscles (except lateral rectus)
- levator palpebrae superioris
what nerve carries parasympathetic fibres for pupil constriction & accomodation?
occulomotor nerve (CNIII)
what occurs if the occulomotor nerve in injured?
- dilated pupil (mydriasis)
- upper eyelid drooping (ptosis)
- eye is turned downwards & outwards
what is the innermost layer of the eye?
the retina
what forms the outer fibrous layer of the eye?
sclera
what lies between the outer sclera and the inner retina?
the vascular choroid layer
what is Glaucoma?
damage to the optic nerve caused by fluid building up in front part of eye (increases pressure inside eye)
- can lead to vision loss
