Lacrimal system Flashcards
3 layers of the tear film
lipid (superficial)
aqueous
mucous (deep)
source of lipid, aqueous and mucus tear films
lipid = meibomian glands aqueous = lacrimal gland mucuous = conjunctival goblet cells
function of lipid tear film
prevent acqueous layer evaporation
function of aqueous tear film
antibacterial activity, washing out debris and suppying cornea with nutrients
function of mucous tear film
aids in spreading tears and stabilising tear film
thickness of lipid, aqueous and mucous tear film
lipid = 0.1 um aqueous = 7.0 um mucus = 0.2 um
pathway of the lacrimal system
lacrimal gland - puncta - canaliculi - lacrimal sac - nasolacrimal duct - inferior nasal meatus
structure of lacrimal gland
tubule-alveolar gland with acini and ducts - 2 parts:
- orbital (in frontal bone)
- palpebral (superiorlaterally in eyelids inferior to levator palpebrae muscle)
function of lacrimal gland
forms aqueous layer of tear film
blood supply to lacrimal gland
lacrimal artery - branch of ophthalmic artery
sensory nerve supply to lacrimal gland
lacrimal nerve (CNVI)
parasympathetic secretomotor nerve supply to lacrimal gland
CNVII - pathway = preganglionic parasympathetic fibres originate from superior salivatory nucleus in the pons and travel with greater petrosal nerve (branch of CNVII) to synapse at pterygopalatine junction - postganglionic fibres then joins the lacrimal branch of CNV1 to supply lacrimal gland
afferent and efferent nerves for lacrimal reflex
afferent = CNVI efferent = CNVII
what do the accessory lacrimal glands do
sustain the basal secretory level of the aqueous layer of the tear film
2 types of accessory lacrimal glands
Krause glands - adjacent to conjunctival fornix, more numerous in upper eyelid
Wolfring glands - in upper border of tarsal plate, larger than Krause glands
what are puncta
small round opening located medially at the posterior edge of the upper and lower lid margins at the junction of the lid’s ciliated and non-ciliated parts
what are the superior and inferior canaliculi comprised of
vertical part (ampulla - 2mm long) horizontal part (8mm long)
where do the superior and inferior canaliculi join together
common canaliculus
what does the junction of the lacrimal sac and common canaliculus contain
Rosenmuller valve - importnat in preventing tear reflux
where is the lacrimal sac located
lacrimal fossa - formed by lacrimal bone and frontal process of the maxilla
what is the nasolacrimal duct
continuation of the lacrimal sac, opens into the inferior meatus in the nose
what does the opening of the nasolacrimal duct contain
fold of mucus - valve of Hasner - prevents air entering the nasolacrimal system during nose blowing
main PC of acquired lacrimal duct obstruction
epiphora (excessive watering of eye)
2 causes of acquired lacrimal obstruction
punctal stenosis (idiopathic or chronic blepharitis) nasolacrimal obstruction (idiopathic, trauma, surgery or tumours)
treatment for punctal stenosis
punctoplasty
treatment for nasolacrimal obstruction
dacryocystorhinostomy (anastomosis of lacrimal sac with mucosa of middle meatus)
where is congenital nasolacrimal duct obstruction usually located
at valve of Hasner
2 features of congenital nasolacrimal duct obstruction
epiphora
mucopurulent discharge on pressure over lacrimal sac
first, second and third line treatments for congenital nasolacrimal duct obstruction
first = observation and massaging of the lacrimal sac for the first 12 months of life
second = nasolacrimal duct probing
third = nasolacrimal duct stent insertion, balloon dilatation or dacryocystorhinostomy
what is canaliculitis
infection of canaliculi - most commonly due to Actinomyces israelii
3 features of canaliculitis
epiphora
red eye
discharge on pressure over the canaliculus
management of canaliuclitis
topical Abx
what is dacryoadenitis
idiopathic lacrimal gland inflammation
main risk factor for dacryoadenitis
tear stasis, secondary causes include viral infections e.g. mumps
potential cause of bilateral dacryoadenitis
sarcoidosis
potential cause of persistence/presence of paraesthesia with dacryoadenitis
carcinoma
4 features of dacryoadenitis
painful/tender/red/swollen lacrimal gland (superolateral upper eyelid)
disturbed tear production
s-shaped ptosis of upper eyelid
downward and inward displacement of the globa
what is dacryocystitis
infection of lacrimal sac due to obstruction in nasolacrimal duct
4 bacteria causing bacryocystitis
s. aureus
s. epidermidis (adults)
s. pneumoniae
h. influenzae (children)
features of acute dacryocystitis
erythematous tender swelling over lacrimal sac with associated epiphora
management of acute dacryocystitis
warm compresses, systemic abx and dacryocystorhinostomy after the acute phase has completely resolved
features of chronic dacryocystitis
epiphora and recurrent unilateral conjunctivitis
management of chronic dacryocystitis
dacryocystorhinostomy
most common lacrimal gland tumour
pleomorphic adenoma of lacrimal gland (benign but can transform to malignant)
featrures of pleomorphic adenoma of lacrimal gland
progressive painless enlargement of upper eyelid with inferonasal dystopia
investigation and treatment of pleomorphic adenoma of lacrimal gland
CT
surgery
main type of lacrimal gland carcinoma
adenoid cystic carcinoma
histopathology of adenoid cystic carcinoma
cribriform (‘Swiss cheese’) growth pattern
2 other types of lacrimal gland carcinoma
pleomorphic adenocarinoma
mucoepidermoid carcinoma
5 features of lacrimal gland carcinoma
rapidly growing and painful lacrimal gland mass inferonasal dystopia optic disc swelling choroidal folds perineural invasion?
what is perineural invasion
spreading of a cancer around a nerve - causing a neurological deficit
4 ways to manage lacrimal gland carcinoma
biopsy
orbital exenteration (surgical removal of globe and surrounding tissue)
radical orbitectomy
radiotherapy
what is Sjogren syndrome
autoimmune condition - salivary and lacrimal glands become infiltrated with lymphocytes and acini are progressively destroyed
triad of features of Sjogren syndrome
xerostomia
keratoconjunctivitis sicca
parotid gland enlargement
other condition commonly present with Sjogren syndrome
posterior blepharitis
type of erosions in Sjogren syndrome
corneal punctate epithelial erosions (stains with fluorescein)
4 investigations for Sjogren syndrome
anti-Ro and anti-La antibodies
reduced tear film breakup time
Schirmer test
ocular staining
what does the schirmer test do
determines whether the eye produces enough tears to keep it moist
what does ocular staining show in Sjogren syndrome
interpalpebral staining of cornea and conjunctiva, rather than a superior or inferior stain pattern (seen in superior limbic keratoconjunctivitis or exposure keratopathy respectively)
first line treatment of Sjogren syndrome
ocular lubricants and artificial tears - including hypromellose (lowest viscosity) carbomer and paraffins (highest viscosity)
second line treatment of Sjogren syndrome
topical corticosteroids and/or oral pilocarpine (increases lacriaml gland secretion)
third line treatment of Sjogren syndrome
punctal occlusion or low-water content bandage contact lenses (e.g. silicone hydrogel)
what is xerophthalmia caused by
severe vitamin A deficiency
5 features of xerophthalmia
nyctalopia xerosis Bitot's spots punctate corneal epithelial erosions keratomalacia in severe cases
what is xerosis
severe conjunctival dryness and keratinization
what are Bitot’s spots
triangular keratinized build up on the conjunctiva
management of xerophthalmia
vit A supplementation and topical lubrication
