Lecture 15– The Eye: Orbit and Lacrimal apparatus (Pt1) Flashcards
orbital cavities
x2
- Pyramidal shaped with apex pointing posteriorly and medially
- House eye balls, extraocular eye muscles, lacrimal apparatus, fat, nerves, blood vessels
how many walls does the orbital cavity have
- 4 walls
- Lateral
- Medial
- Mostly the ethmoid and lacrimal bone
- Roof
- Floor
- Mostly the maxillary
- Base of pyramid faces
anteriorly- tough orbital rim
number of openings into/out of orbit
main arterial supply to orbit
- Ophthalmic artery (first branch off the internal carotid sinus after cavernous sinus) and subsequent branches
- Comes into the eye via the optic canal
- Including central retinal artery
Main venous supply of the orbit
- Ophthalmic veins (superior and inferior)
- Drains venous blood into cavernous sinus, pterygoid plexus and facial vein
- Via the superior and inferior orbital fissures
Nervous supply of contents of orbit
- Special sensory vision from retina- Optic nerve – CN II
- General sensory (touch, pain) from the eye (including conjunctive and cornea)- Ophthalmic division of Trigeminal nerve- CN Va
- Motor nerves to muscles (extraocular muscles)
- Oculomotor
- Trochlear
- Abducens
the floor of the orbita has a close anatomical relationship
inferiorly with the maxiallary air sinues (paranasal air sinus)
medial wall has a close anatomical relationship with
ethmoid bone
- Air filled cavities near the ethmoid (paranasal air sinus)
roof has a close anatomical relationship with
- rbital plates of frontal bone
- Superior relationship- anterior cranial fossa and forntal lobe house within it
another important anatomical relation of the orbit
- Nasal cavity also important anatomical relationship- connection between the orbit and nasal cavity by the nasolacrimal duct
Implications for: orbital trauma and spread of infection
……….. and ………….of orbit are the weakest parts of the orbital cavity
Medial wall and floor of orbit are the weakest parts of the orbital cavity
- Ethmoid and maxillary bone have paranasal air sinuses- more prone to fracture
- Floor of orbit weakest
orbital blow out fracture
- Sudden increase in infraorbital pressure (e.g. from retropulsion of eye ball (globe) by fist or ball) fractures floor of orbit (maxilla)
- Opacity= blood
CT and x-ray of orbital blow out fracture
- Orbital content can prolapse and bleed into maxillary sinus
- Fracture site can trap structures e.g. soft tissue extraocular muscle located near orbital floor
- Prevents upward gaze on affected side
presentation of orbital blow out fracture
- hisotry of trauma to the eye/orbit
- periorbital swelling\
- painful
- double vision- worse on vertical gaze
- numbness over cheek, lower eyelid and upp lip (and upper teeth ad gums) on effacted side
eyelids function
protect the eye
eyelids are made up of a number of different tissues
- Skin (most superficially)
- Loose subcutaneous tissue
- Orbicularis oculi (palpebral part)- CN VII)
- Protects front of eye
- Tarsal plate
- Levator palpebrae superioris muscle
- Arises from within orbital cavity and swings forwards anterior becomes aponeurotic and blends into tissue of upper eyelid
- Retracts and elevates eyelid
- Small smooth muscle components- mullers muscle- small contribution to elevation of the lid via sympathetic action
- Bulk of muscle- CN III – oculomotor
-
Glands (contribute to tear film)
- Prevents damage
- Meibomian glands
- Sebaceous glands associated with lash follicle
- These can become blocked problems related to eyelids
- Prevents damage
stye
sebaceous gland blockages
- Superficial blockage
- Painful lump usually in upper eyelid
- White head
- Localised infection – staphylococcus
chalazian
- Meibomian gland cyst
- Deeper blockage
- Painless
- Not caused by infection
- Just blockage
- 1/3 resolve of on own
- Treatment: warm compress and cleaning along eyelid margin
- No Abx
- Blepharitis
- Blockage of glands along the eyelid margin
- More extensive
- Less of a localised lump
- Gritty crusting along eyelid margin
- Simple eyelid hygiene
- Warm compress
- Margin
- Cleaning
Orbital septum
Thin sheet of fibrous tissue originating from orbital rim periosteum blends with tarsal plates
- Orbital septum and tarsal plates
- separate subcutaneous tissue of eyelid and orbicularis oculi muscle from infraorbital contents
- Acts as a barrier against superficial infection spreading from the pre-septal dn post-septal space (orbital cavity proper)
Periorbital (pre-septal) cellulitis
Infection occurring within eyelid tissue, superficial to orbital septum
- Secondary to superficial infection e.g. bites, wounds
- Confined to tissues superficial to orbital septum and tarsal plates
- Therefore:
- Ocular function- eye movement and vision remains unaffected
- Can be difficult to differentiate between peri-orbital and more severe orbital cellulitis
- If in doubt refer urgently- high dose IV antibiotics and surgical drainage
Orbital (post-septal) cellulitis
Infection WITHIN the orbit posterior or deep to the orbital septum
- Can arise from pre-septal cellulitis
- Usually arises from infection from within the orbit
- Signs
- Proptosis/ exophthalmos- eye pushed forward
- Reduced +/- painful eye movement
- Reduced visual acuity (optic nerve involved)
-
Most dangerous
- Inferior and superior ophthalmic veins can spread infection to the cavernous sinus causing intracranial infections
- Varbous sinus thrombosis
- Meningitis
- Treatment
- Abx
- Surgery
- Inferior and superior ophthalmic veins can spread infection to the cavernous sinus causing intracranial infections
postseptal (orbital) is
risk to optic nerve (sight threatening) - risk of intracranial spread
Contents of orbital cavity
- Nerve sand blood vessels
- Fat +++
- Lacrimal apparatus-production and drainage of tears
- Eyeball (globe)
- Extraocular muscles
situation of the eyeball (globe)
- Globe does not sit on the floor of the orbit
eyeball position maintained by
- Suspensory ligament of lockwood- sits under like a sling
- Extraocular muscles
- Orbital fat ++
Tear film and lacrimal apparatus
Refers to
structures involved in tear film production and drainage
tear film is
Important fluid to ensure anterior surface of the eye (conjunctiva and cornea) are kept lubricated and hydrated
- Protects surface of the eye
how does the tear film protext the surface of the eye
- Blinking washes film over eye and washes debris away
tear film has how many layers
oily
water
mucus
which gland is responsible for the oil in the tearfilm
meibomian glands- within tarsal plates of upper and lower eyelids
which gland is responsible for the water in the tearfilm
lacrimal gland -found deep to the orbital septum, closely related to the lateral edge of the Levator palpebral superioris
which cell is responsible for the mucus in the tearfilm
goblet cells within the conjunctiva- transparent membrane over surface of the eye
- Drainage of tear film through
small ducts made up of the lacrimal punctum (which you can see if you pull inferior tarsal plate down) and the lacrimal canaliculus which drains into the nasolacrimal duct
Obstruction of the lacrimal apparatus
*
- Injury to medial aspect of eye
- Scarring and fibrosis – obstruct drainage
- Leads to overflow of tears over lower eyelid- epiphora.
