Tears and Lacrimation

Question 1

Describe the lacrimal apparatus

Answer 1

Lacrimal gland which produces most tears
Lacrimal lake
Lacrimal cannaliculi
Lacrimal sac
Nasolacrimal duct which carry tears into the nasal cavity

Question 2

What are the components of tears? What are the volume of tears?

Answer 2

Lipid layer, aqueous layer, mucus layer
Similar in electrolyte concentration to plasma but rich in IgA
Also contain lysozyme and beta-lysin which have antibacterial properties

6 microlitres

Question 3

What glands produce tears?

Answer 3

Meibomian glands
Conjunctival glands
Goblet cells
Lacrimal glands

Question 4

What is reflex lacrimal secretion? Nerve?

Answer 4

From lacrimal gland via parasympathetic nerve fibres of trigeminal nerve

Question 5

What causes dry eyes?

Answer 5

Reduced tear production by lacrimal glands in old age
Sjogren’s syndrome (associated with CT disorders), mumps, sarcoidosis, amyloidosis, lymphoma, leukaemia, haemochromatosis

Other causes:
Excess evaporation of tears (post-exposure keratitis), mucin deficiency in tears

Question 6

What test for dry eyes? Management

Answer 6

Schirmers test - strip of filter paper put overlapping lower lid - tears should soak >15mm in 5mins) - reveals reduced production.

Artificial tears for symptom relief

Outflow of tears in dry eyes restricted using lubricating drops or reducing size of the puncture lacrimale by plugs. by cautery or by laser

Question 7

What can cause watery eyes?

Answer 7

Decreased drainage
- Punctal stenosis, obstruction
Increased lacrimation
- both eyes?, environment dust or irritant, corneal injury tears contain increased nerve growth factor which aid healing,
Pump failure
- on blinking, positive and negative pressure is created in lacrimal sac which sucks tears into it. This is the tear pump
Gravity helps keep the sac empty - look for causes such as entropion, ectropion or CNS - myasthenia,)

Question 8

Describe innervation of the lacrimal glands

Answer 8

Parasympathetic secretion from lacrimal nucleus of facial nerve in pons
Sympathetic fibres from superior cervical ganglion

Question 9

What is causes persistent watery eye in infant? Management?

Answer 9

Imperforate membrane at lower end of lacrimal duct causing nasolacrimal duct obstruction.

Teach parents to massage the lacrimal duct
Symptoms should resolve by 1, if not - probing