Anatomy of the Orbit, Eyelids and Lacrimal System Flashcards
What bones make up the orbit?
Frontal Sphenoid Ethmoid Maxilla Zygomatic Lacrimal
Which parts of the orbit are particularly susceptible to fracture?
Inferior and Medial parts
What is the function of the eyelid?
Protect cornea and eyeball from injury
Keep cornea moist by covering in tear film
What muscles move the eyelids and what innervates each muscle?
Orbicularis Oculi - facial nerve (VII)
Levator Palpabrae Superioris - oculomotor nerve (III)
What is a stye?
Infection of the glands of Zeiss, Moll or of the eyelash follicle
Commonly caused by staph aureus
What is a chalazion?
Painless swelling of the eyelid - caused by blockage of the tarsal gland
Also known as meibomian cyst
What makes up the lacrimal apparatus?
Lacrimal glands
Lacrimal ducts
Lacrimal canaliculi
How do tears flow through the lacrimal apparatus?
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
What happens if there is a blockage in the lacrimal apparatus?
No anastomosis so there is an overflow of tears - epiphora
Why are tears important?
Provide smooth surface for light rays to refract uniformly
Provide lubrication - prevent dry eyes
What can dry eyes cause?
Damage to epithelial surface of cornea and conjunctiva –> sensation of grittiness
Risk of infection
What should you consider if dry eyes are caused by reduced tear production?
Autoimmune causes - Sjogrens, RA
Medication - Anti-histamines
How can injury to the facial nerve lead to excess tear production?
Orbicularis oculi paralysis –> eyelid partially open and lose protective blinking –> cornea dry and unprotected from dust –> irritation of eyeball lead to excess tear formation
How may patients with a blowout fracture present?
Sunken orbits - pain
Reduced eye movement
Double vision
Loss of sensation to cheeks and upper gum - lose infraorbital nerve
What is seen on X-Ray in a blowout fracture?
Teardrop sign
What vasculature is important in ophthalmology?
Ophthalmic artery - from internal carotid
Central retinal artery - from ophthalmic artery - internal surface of retina
Ophthalmic vein - drain into cavernous sinus
What are the foramen in the orbit?
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
What are the common causative organisms of conjunctivitis?
Adenovirus
Staph
Strep pneumoniae
H Influenzae
How does bacterial conjunctivitis present?
Thick purulent discharge
Eyes stick together
How does viral conjunctivitis present?
Serous discharge
Recent URTI
Periauricular lymph nodes
If conjunctivitis persists for more than 7 days, what should be done?
Swab
What are the general features of conjunctivitis?
Bilateral
Generalised red eye
Irritated gritty feeling
History of close contact
How is viral conjunctivitis managed?
Self limiting within 2 weeks
Can use lubricant drops and warm water
Careful sharing towels
How is bacterial conjunctivitis managed?
Antibiotics if severe
Delayed prescribing of Chloramphenicol (if not resolved after 3 days)
How does conjunctivitis due to chlamydial infection present?
Mild infection Moderately thick discharge Periauricular lymphadenopathy Lid follicles Sexual history Poor response to Abx
How does gonococcal conjunctivitis present?
Severe hyperactive hyperpurulent discharge
Rapid keratitis
Highly infection - require contact tracing
What is allergic conjunctivitis?
Type 1 hypersensitivity reaction with mast cell degranulation and histamine release
Can be perennial, season or atopic
Common allergens to allergic rhinitis
How does allergic conjunctivitis present?
Itchy watery red eye with lid oedema
Large papillae under eyelids
Degree of blepharitis
How is allergic conjunctivitis managed?
Systemic and topical antihistamines
Cool eye baths
Topical mast cell stabilisers
How are dry eyes managed?
Lid hygiene
Treat underlying cause
Drops, gels and ointments (at night as cause blurring)
Further management - steroids, punctual plugs, surgery
What is ectropion?
Eversion of the lid margin leading to corneal and conjunctival exposure
What causes ectropion?
Age related condition
Tumour push eyelid out
CN VII palsy
How does ectropion present?
Irritated red eye
How is ectropion managed?
Surgery
Lubricants can be useful while waiting for surgery
What is an entropion?
Inversion of eyelid leading to corneal and conjunctival irritation
What causes entropion?
Age related
Muscle spasm - ocular irritation
Trachoma
How does entropion present?
FB sensation
Red
Irritated
How is entropion managed?
Surgery only corrective option
Can tape eye while waiting
What is trichiasis?
Eyelashes misdirected and in contact with ocular surface
What causes trichiasis?
Following inflammation and scarring of eyelash follicle
How is trichiasis managed?
Remove lashes with epilation or cryotherapy
