Insufficient drainage of tears
a. Anatomical blockage of the tear duct – based on location:
i. Punctal Stenosis – Lacrimal punctum is the name of the opening of the tear duct on the eyelid margin. The punctum can get blocked any time there is inflammation present on the eyelid margin, as it occurs with dry eyes, allergies, glaucoma medication, ectropion, eyelid laxity, eyelid retraction etc. The rest of the lacrimal duct is usually open, and a simple office procedure called punctoplasty can be performed to open the blocked punctum. However, if the underlying cause of inflammation is not addressed, the rate of recurrence is over 50%.
ii. Canalicular Stenosis – Lacrimal Canaliculus is the name of the small tear duct present inside each eyelid that connects the punctum with the lacrimal sac. Even though there are 2 canaliculi per eye, the disease process that leads to the blockage of the canaliculus tends to affect both the upper and the lower ducts. Most common causes are viral conjunctivitis, allergies, certain cancer medications and many different types of eye drops, especially those used to treat glaucoma (high eye pressure). Treatment of canalicular stenosis can sometimes be very difficult because of the high recurrence rate and needs to be done on an individualized basis, depending on the location and the degree of stenosis. When complete canalicular stenosis is present, a permanent tube called Jones tube is used like a stent to create a direct communication between the inner corner of the eye and the nose.
Congenital Nasolacrimal Duct Obstruction (cNLDO) – Approximately 7% of babies are born with congenital obstruction of the tear drainage system in the nose (the Nasolacrimal duct). This resolves itself in the first year of life in over 90% of cases as the Valve of Hasner begins to spontaneously open. In the 10% of infants where the valve does not open by 1 year of age, a quick procedure can to be done to open it. In rare instances, the bony nasolacrimal duct is partly or completely absent, in which case an endoscopic bypass (Dacryocystorhinostomy) needs to be done around 4 years of age.
Primary Acquired Nasolacrimal duct obstruction (PANDO) – In adults, the most common causes of NLDO are atmospheric pollution, medication, chronic nasal inflammation, allergies, chronic sinusitis and nasal trauma. PANDO leads to tearing and mucus discharge from the eye that can significantly alter one’s quality of life and impair daily activities. The most common complication of PANDO is lacrimal sac infection called Dacryocystitis. This occurs in the majority of patients that have chronic nasolacrimal duct obstruction and can happen at any time. Lacrimal obstruction in adults never resolves itself and a surgical intervention called Dacryocystorhynostomy (DCR) is required. Typically, this procedure is done using an endoscope and has a success rate of over 95%.
b. Functional blockage of the tear duct – lacrimal pump failure secondary to:
i. Facial paralysis – Regardless of whether you recover or not from facial paralysis (Facial Palsy, Bell’s Palsy), the lacrimal pump situated in the inner corner of the eye does not function properly. The tear duct is anatomically open, but the absence of pump function leads to the stagnation of tears in the eye and constant watering. This condition can be dramatically improved by injecting Botox in the eyelid (if aberrant regeneration is present) or by correcting the paralytic ectropion (whenever the case).
ii. Eyelid laxity – The lacrimal pump depends on the proper horizontal tightness of the eyelids. Any disease or condition that makes the eyelids become loose can impair the functioning of the lacrimal pump and result in tearing. Floppy Eyelid Syndrome (FES) is a condition that results in extreme eyelid laxity and is seen in the majority of patients suffering from Obstructive Sleep Apnea (OSA). The use of the CPAP machine in these patients can slow down or even halt the progression of eyelid laxity.
iii. Ectropion (eyelid turned out) – An eyelid turned outwards can lead to chronic tearing by 3 mechanisms. First, the eye becomes exposed to the air which makes it drier and irritated. Consequently, the lacrimal gland produces an excessive amount of tears. Second, the lacrimal punctum does not come any longer in contact with the tear lake when the eyelid turns out. And, third, the lacrimal pump does not function in the presence of a loose eyelid turned outwards. All 3 mechanisms need to be addressed in order to obtain an adequate improvement in tearing. Sometimes, a 4th mechanism is associated: punctal stenosis from the chronic inflammation of the eyelid exposed to the air. This is usually resolved at the same setting.
iv. Eyelid retraction – When the eyelid is pulled downwards from various pathologies it does not protect the eyeball and does not function as a good windshield wiper, resulting in a dry and irritated eye. This results in a reflex overproduction of tears by the lacrimal gland. Frequently, the lacrimal pump is also impaired due to the associated eyelid laxity, further exacerbating the tearing. Proper correction of any eyelid malposition (adequate eyelid position) is mandatory to improve tearing in theses cases.