26 - Eye and Orbit Flashcards
(39 cards)
What bones make up the margin of the orbit?
- frontal
- maxilla
- zygomatic
What bones make up the walls of the orbit?
- frontal
- maxilla
- zygomatic
- lacrimal
- ethmoid
- sphenoid
- palatine (minor)
What are the main openings into the orbit?
- superior orbital fissure
- inferior orbital fissure
- nasolacrimal canal
- optic canal
What structures pass through the inferior orbital fissure?
Inferior ophthalmic vein
What structures pass through the superior orbital fissure?
- trochlear nerve
- abducent nerve
- opthalmic nerve branches (CNV1)
- occulomotor nerve
What structures pass through the optic canal?
- optic nerve
- opthalmic artery
What structures pass through the nasolacrimal canal?
Nasolacrimal duct
Which branches of CN V1 pass through the superior orbital fissure?
- frontal
- lacrimal
- nasocillary
Which branches of CN III pass through the superior orbital fissure?
- superior
- inferior
Describe the structure of the optic nerve.
- surrounded by cranial meninges
- contains central retinal artery and vein
What are the contents of the orbit?
- eyeball
- retrobulbar fat
- optic nerve
- extraocular muscles
- eyelids and lacrimal apparatus
Describe how the optic nerve enters the skull.
- leave the brain as the two optic tracts
- meet at the optic chiasm as they enter the skull
- enter the skull as the two optic nerves
What is papilloedema?
- raised intracranial pressure is transmitted to the meninges surrounding the eye
- venous drainage of the eye slows
- causes swelling of the optic disc
What is amaurosis fugax?
- when the central retinal artery becomes occluded
- painless and temporary loss of vision
Describe how injury to the optic nerve affects the visual field.
- vision is lost completely in one eye
- nerve from both sides of the brain are damaged
Describe how injury to the optic chiasm affects the visual field.
- tunnel vision
- lateral vision is lost as the nerves from both sides cross over
Describe how injury to the optic tract affects the visual field.
- field of vision on the contralateral side is lost
- injury before the tract crosses over
Where is the lacrimal gland located?
Upper lateral corner of orbit
Describe the drainage of the lacrimal gland.
- tears released in the upper lateral corner of the eye
- washed over the eye by the orbicularis oculi
- form a lake in the medial corner of the eye (lacrimal caruncle)
- drain via puncta to the lacrimal sac and then to the nasolacrimal duct
- drains into inferior nasal meatus
Describe the parasympathetic innervation of the lacrimal gland.
- preganglionic fibres from nervus intermedius (CN VII)
- travel in greater petrosal nerve, then nerve of pterygoid canal
- arrive at the pterygopalatine ganglion
- postganglionic fibres via zygomatic branch (CN V2) to lacrimal gland
What are the extraocular muscles?
- superior oblique
- inferior oblique
- medial rectus
- lateral rectus
- superior rectus
- inferior rectus
- levator palpebrae superioris
Describe the origin and insertion of the extraocular muscles.
- all originate from the common tendinous ring at the posterior of the orbit
- EXCEPT the inferior oblique which originates from the maxilla
- all insert to the sclera
What muscle pulls the eye medially?
Medial rectus
What muscle pulls the eye medial and superiorly?
Superior rectus
