ALacrimation is watering due to over-production by the lacrimal gland, whereas epiphora is watering due to impairment of the lacrimal drainage system.natomy and physiology
The main lacrimal gland lies in the lacrimal fossa in the upper outer quadrant of the orbit. Tear secretions reach the surface of the eye via 14 or so ductules from the gland and are distributed over the ocular surface by the blinking action of the eyelids.
After making their way over the surface of the eye, the tears drain into the puncta, at the medial ends of the eyelids. The puncta open into canaliculi, 8 - 10mm in length. It is estimated that 70% of tears drain through the lower and 30% through the upper canaliculus. These unite at the medial canthus to form a common canalicus, 4mm long, which drains into the lacrimal sac. The sac is in turn drained by the nasolacrimal duct into the lower reaches of of the nasal cavity. The action of blinking provides a pumping mechanism. From the sac the tears drain by gravity to the nose.
Causes of lacrimation
1. Environmental factors eg dust, smoke, wind. These will always aggravate weeping due to the other causes. 2. Corneal irritation eg ulcer, foreign body. 3. Conjunctival irritation eg conjunctivitis. 4. Lid margin disease (blepharitis). 5. Dental or sinus disease. 6. Migrainous neuralgia (cluster headache). 7. Crocodile tears are caused by facial nerve lesions proximal to the geniculate ganglion. Salivary fibres regenerate into the greater superficial petrosal nerve and the eye waters in response to gustatory stimuli.
Causes of epiphora
1. Pump failure eg facial palsy. 2. Punctal malposition eg ectropion. 3. Punctal stenosis. 4. Canalicular obstruction. 5. Nasolacrimal duct obstruction (the commonest cause by far). 6. Nasal or sinus disease.
John Pitts is an oculoplastic surgeon in full-time private practice in London and Barbados following a substantive NHS consultant position. He graduated MB ChB from Glasgow University in 1983 and, in 1987, after working in pathology and neurology, he trained in ophthalmology in Glasgow, Nottingham and London. He has travelled extensively, working in centres of excellence in Los Angeles, New Orleans, Melbourne, Barbados, Brunei and Vancouver. He has undertaken Fellowship training in oculoplastics at Moorfields Eye Hospital.
