Anatomy of the Orbit, Eyelids and Lacrimal System

Question 1

What bones make up the orbit?

Answer 1

Frontal
Sphenoid
Ethmoid
Maxilla
Zygomatic
Lacrimal

Question 2

Which parts of the orbit are particularly susceptible to fracture?

Answer 2

Inferior and Medial parts

Question 3

What is the function of the eyelid?

Answer 3

Protect cornea and eyeball from injury

Keep cornea moist by covering in tear film

Question 4

What muscles move the eyelids and what innervates each muscle?

Answer 4

Orbicularis Oculi - facial nerve (VII)

Levator Palpabrae Superioris - oculomotor nerve (III)

Question 5

What is a stye?

Answer 5

Infection of the glands of Zeiss, Moll or of the eyelash follicle

Commonly caused by staph aureus

Question 6

What is a chalazion?

Answer 6

Painless swelling of the eyelid - caused by blockage of the tarsal gland

Also known as meibomian cyst

Question 7

What makes up the lacrimal apparatus?

Answer 7

Lacrimal glands
Lacrimal ducts
Lacrimal canaliculi

Question 8

How do tears flow through the lacrimal apparatus?

Answer 8

Gland produce components of tears and secrete onto eye through the lacrimal duct

Pass through lacrimal lake at medial angle of eye

Pass to nasal cavity through nasolacrimal duct

Swallowed

Question 9

What happens if there is a blockage in the lacrimal apparatus?

Answer 9

No anastomosis so there is an overflow of tears - epiphora

Question 10

Why are tears important?

Answer 10

Provide smooth surface for light rays to refract uniformly

Provide lubrication - prevent dry eyes

Question 11

What can dry eyes cause?

Answer 11

Damage to epithelial surface of cornea and conjunctiva –> sensation of grittiness

Risk of infection

Question 12

What should you consider if dry eyes are caused by reduced tear production?

Answer 12

Autoimmune causes - Sjogrens, RA

Medication - Anti-histamines

Question 13

How can injury to the facial nerve lead to excess tear production?

Answer 13

Orbicularis oculi paralysis –> eyelid partially open and lose protective blinking –> cornea dry and unprotected from dust –> irritation of eyeball lead to excess tear formation

Question 14

How may patients with a blowout fracture present?

Answer 14

Sunken orbits - pain
Reduced eye movement
Double vision
Loss of sensation to cheeks and upper gum - lose infraorbital nerve

Question 15

What is seen on X-Ray in a blowout fracture?

Answer 15

Teardrop sign

Question 16

What vasculature is important in ophthalmology?

Answer 16

Ophthalmic artery - from internal carotid
Central retinal artery - from ophthalmic artery - internal surface of retina
Ophthalmic vein - drain into cavernous sinus

Question 17

What are the foramen in the orbit?

Answer 17

Optic canal - optic nerve and ophthalmic artery

Superior orbital tissue - CN III, IV, VI, ophthalmic branch of trigeminal, superior orbital vein

Inferior orbital fissure - inferior orbital vein

Question 18

What are the common causative organisms of conjunctivitis?

Answer 18

Adenovirus
Staph
Strep pneumoniae
H Influenzae

Question 19

How does bacterial conjunctivitis present?

Answer 19

Thick purulent discharge

Eyes stick together

Question 20

How does viral conjunctivitis present?

Answer 20

Serous discharge
Recent URTI
Periauricular lymph nodes

Question 21

If conjunctivitis persists for more than 7 days, what should be done?

Answer 21

Swab

Question 22

What are the general features of conjunctivitis?

Answer 22

Bilateral
Generalised red eye
Irritated gritty feeling
History of close contact

Question 23

How is viral conjunctivitis managed?

Answer 23

Self limiting within 2 weeks
Can use lubricant drops and warm water
Careful sharing towels

Question 24

How is bacterial conjunctivitis managed?

Answer 24

Antibiotics if severe

Delayed prescribing of Chloramphenicol (if not resolved after 3 days)

Question 25

How does conjunctivitis due to chlamydial infection present?

Answer 25

``` Mild infection Moderately thick discharge Periauricular lymphadenopathy Lid follicles Sexual history Poor response to Abx ```

Question 26

How does gonococcal conjunctivitis present?

Answer 26

Severe hyperactive hyperpurulent discharge Rapid keratitis Highly infection - require contact tracing

Question 27

What is allergic conjunctivitis?

Answer 27

Type 1 hypersensitivity reaction with mast cell degranulation and histamine release Can be perennial, season or atopic Common allergens to allergic rhinitis

Question 28

How does allergic conjunctivitis present?

Answer 28

Itchy watery red eye with lid oedema Large papillae under eyelids Degree of blepharitis

Question 29

How is allergic conjunctivitis managed?

Answer 29

Systemic and topical antihistamines Cool eye baths Topical mast cell stabilisers

Question 30

How are dry eyes managed?

Answer 30

Lid hygiene Treat underlying cause Drops, gels and ointments (at night as cause blurring) Further management - steroids, punctual plugs, surgery

Question 31

What is ectropion?

Answer 31

Eversion of the lid margin leading to corneal and conjunctival exposure

Question 32

What causes ectropion?

Answer 32

Age related condition Tumour push eyelid out CN VII palsy

Question 33

How does ectropion present?

Answer 33

Irritated red eye

Question 34

How is ectropion managed?

Answer 34

Surgery Lubricants can be useful while waiting for surgery

Question 35

What is an entropion?

Answer 35

Inversion of eyelid leading to corneal and conjunctival irritation

Question 36

What causes entropion?

Answer 36

Age related Muscle spasm - ocular irritation Trachoma

Question 37

How does entropion present?

Answer 37

FB sensation Red Irritated

Question 38

How is entropion managed?

Answer 38

Surgery only corrective option | Can tape eye while waiting

Question 39

What is trichiasis?

Answer 39

Eyelashes misdirected and in contact with ocular surface

Question 40

What causes trichiasis?

Answer 40

Following inflammation and scarring of eyelash follicle

Question 41

How is trichiasis managed?

Answer 41

Remove lashes with epilation or cryotherapy