Excessive production of tears – reflex tearing
a. After facial paralysis – Aberrant regeneration of the facial nerve after VII nerve palsy (Bell’s palsy) can lead to a branch of the trigeminal nerve (the 5th cranial nerve involved in chewing) being mis-wired to innervate the lacrimal gland. Consequently, the eye starts to water spontaneously during eating. This condition cannot be prevented but can be successfully treated with Botox injections into the lacrimal gland.
b. Trichiasis (misdirected lashes) – Any eyelash rubbing on the eyeball leads to the reflex over-production of tears. This condition can be treated by permanently removing the offending lashes in the office with a special radiofrequency device.
c. Entropion (Eyelid turned in) – When the entire eyelid is turning in, a condition known as entropion, the eyelashes and the lid margin can rub severely against the eyeball resulting in irritation and sometimes a corneal ulcer. The lacrimal gland immediately starts producing tears in an effort to relieve the irritation. Untreated, entropion can result in corneal scarring and permanent vision loss.
d. Dry eyes – A great number of conditions can result in dry eye syndrome or simply dry eyes. Systemic diseases such as Sjögren’s, Reumatoid arthritis, Lupus and Graves disease are among the most common. Dry eyes is also an occupational disease encountered in over 60% of the population today. The combination of computers, smart-phones and air conditioning can all impair the ocular surface for which reason the dry eye syndrome is now seen in many young people, including children. Dry eyes is a frequent cause of reflex tearing (secondary to eye irritation) in which case it is often mis-diagnosed and treated as conjunctivitis. Dry eyes can also result from anatomical problems related to the eyelids’ role as windshield wipers. Eyelid malpositions (abnormal eyelid position) usually need to be corrected, otherwise the use of artificial tear drops and ointments has only a minimal benefit. The most common eyelid problems leading to dry eyes and consecutive tearing are:
i. Ectropion (eyelid turned out) – when the lower eyelid turns outward, it doesn’t protect the eyeball any more and it doesn’t function as a windshield wiper to lubricate the eye. Consequently, the eye surface gets dry and irritated which triggers an overproduction of tears from the lacrimal gland. This results in watery eyes, worse when reading, watching TV or working on the computer. Patients are frequently misdiagnosed as having a conjunctivitis and are given antibiotic-steroid drops that do more harm than good. The only therapeutic option for ectropion is surgical repair which corrects the dry eye syndrome and reactivates the lacrimal pump.
ii. Eyelid laxity – When the eyelids become loose from different pathologies, they don’t protect and lubricate the eyes as they should, and the eyes become dry. Through a trigeminal reflex, the lacrimal gland is stimulated to produce an excess of tears and the eyes become watery. However, the eyes feel more dry than wet and the episodes of tearing are usually preceded by dry eye symptoms such as: irritation, burning, itching and blurry vision.
iii. Eyelid retraction – When the upper and/or lower eyelid is retracted and not protecting the eyeball, dry eyes and irritation occur, which triggers the production of tears by a reflex mechanism. Unfortunately, these tears are not of good quality because they are produced by the lacrimal gland and are too watery. This is the reason why, when one cries because of feeling sad, the eyes become red and irritated. Using artificial tears that are lubricating can temporarily relieve the symptoms and paradoxically block the tearing. However, permanent correction of the eyelid retraction is usually necessary.
e. Allergies – There are two mechanism by which allergies lead to watery eyes. The itching and irritation produced by the release of inflammatory molecules onto the ocular surface leads to reflex tearing. In addition, the inflammation throughout the lacrimal drainage system can frequently lead to anatomical blockage (obstruction) of the tear duct. This can happen anywhere from the punctum to the nasolacrimal duct and can be permanent. Sometimes, rapid and effective intervention can decrease the inflammation and allow the tear duct to reopen. The treatment is usually with allergy eye drops but surgical intervention is sometimes necessary.