Lecture 15– The Eye: Orbit and Lacrimal apparatus (Pt1) Flashcards
(37 cards)
1
Q
orbital cavities
A
x2
- Pyramidal shaped with apex pointing posteriorly and medially
- House eye balls, extraocular eye muscles, lacrimal apparatus, fat, nerves, blood vessels
2
Q
how many walls does the orbital cavity have
A
- 4 walls
- Lateral
- Medial
- Mostly the ethmoid and lacrimal bone
- Roof
- Floor
- Mostly the maxillary
3
Q
- Base of pyramid faces
A
anteriorly- tough orbital rim
4
Q
number of openings into/out of orbit
A
5
Q
main arterial supply to orbit
A
- 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
6
Q
Main venous supply of the orbit
A
- Ophthalmic veins (superior and inferior)
- Drains venous blood into cavernous sinus, pterygoid plexus and facial vein
- Via the superior and inferior orbital fissures
7
Q
Nervous supply of contents of orbit
A
- 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
8
Q
the floor of the orbita has a close anatomical relationship
A
inferiorly with the maxiallary air sinues (paranasal air sinus)
9
Q
medial wall has a close anatomical relationship with
A
ethmoid bone
- Air filled cavities near the ethmoid (paranasal air sinus)
10
Q
roof has a close anatomical relationship with
A
- rbital plates of frontal bone
- Superior relationship- anterior cranial fossa and forntal lobe house within it
11
Q
another important anatomical relation of the orbit
A
- 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
12
Q
……….. and ………….of orbit are the weakest parts of the orbital cavity
A
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
13
Q
orbital blow out fracture
A
- Sudden increase in infraorbital pressure (e.g. from retropulsion of eye ball (globe) by fist or ball) fractures floor of orbit (maxilla)
- Opacity= blood
14
Q
CT and x-ray of orbital blow out fracture
A
- 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
15
Q
presentation of orbital blow out fracture
A
- 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
16
Q
eyelids function
A
protect the eye
17
Q
eyelids are made up of a number of different tissues
A
- 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
18
Q
stye
A
sebaceous gland blockages
- Superficial blockage
- Painful lump usually in upper eyelid
- White head
- Localised infection – staphylococcus
19
Q
chalazian
A
- 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
20
Q
- Blepharitis
A
- 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
21
Q
Orbital septum
A
Thin sheet of fibrous tissue originating from orbital rim periosteum blends with tarsal plates
22
Q
- Orbital septum and tarsal plates
A
- 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)
23
Q
Periorbital (pre-septal) cellulitis
A
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
24
Q
Orbital (post-septal) cellulitis
A
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
25
postseptal (orbital) is
risk to optic nerve (sight threatening) - risk of intracranial spread
26
**Contents of orbital cavity**
* **Nerve sand blood vessels**
* **Fat +++**
* **Lacrimal apparatus-**production and drainage of tears
* **Eyeball (globe)**
* **Extraocular muscles**
27
situation of the eyeball (globe)
* Globe does not sit on the floor of the orbit
28
eyeball position maintained by
* Suspensory ligament of lockwood- sits under like a sling
* **Extraocular muscles**
* **Orbital fat ++**
29
**Tear film and lacrimal apparatus**
Refers to
structures involved in tear film production and drainage
30
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
31
how does the tear film protext the surface of the eye
* Blinking washes film over eye and washes debris away
32
tear film has how many layers
oily
water
mucus
33
which gland is responsible for the oil in the tearfilm
meibomian glands- within tarsal plates of upper and lower eyelids
34
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
35
which cell is responsible for the mucus in the tearfilm
goblet cells within the conjunctiva- transparent membrane over surface of the eye
36
* 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
37
**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.
