Tears are an essential aspect of maintaining vision. Without tears, the cornea cannot serve its purpose to refract light onto the retina. The clarity and refractive power of the cornea depend on a smooth hydrated surface maintained by tears.
Tears also contain nutrients and protective immune factors that feed and protect the cornea and conjunctiva from damage and infection.
Tears are made up of 3 elements: watery secretions, mucous, and oil. The watery secretions, produced by the lacrimal glands, provide hydration, nutrients and immune protection. Mucous (“mucin”), produced by goblet cells in the conjunctiva, works as a surfactant to facilitate smooth, even distribution of tears on the surface of the eye. Oil is produced by the meibomian glands at the margin of each eyelid, and serves to reduce evaporation and lubricate the eye during blinking.
As the tears flow across the surface of the eye, facilitated by blinking, they are collected by channels that ultimately empty into the back of the nose and throat. The tear drainage system is quite complex, relying on negative pressure produced by muscles in the inner corner of the eyelids to such tears through a tiny drain (“punctum”) into a minute canal (canaliculus), into a collecting sac (“lacrimal sac”), down a mucous membrane-lined bony canal (“nasolacrimal duct”) to the back of the nose and through.
When patients suffer from tearing, it is caused either by overproduction of tears, or inadequate drainage. In the case of overproduction, dry or irritated eyes signal increased production of tears from the lacrimal gland – more than what your drainage system can handle. Often, simple changes such as increased artificial tear use or allergy drops can solve this problem. Other times, a surgical approach to fixing the ocular irritant, such as eyelid laxity or eyelid malposition, is required to alleviate the tearing. You can think of the eyelids as a sort of “windshield wiper” – if the wiper is old and lax, it leaves streaks on the windshield and the view becomes poor; renewing/tightening the windshield wiper – the eyelid – can improve ocular surface protection, reduce the irritation that drives excessive tear production, and also improve the lacrimal pump function, which will improve tear drainage.
In the case of inadequate tear drainage, there is a blockage somewhere within the lacrimal drainage system (puncta, canaliculi and nasolacrimal duct). This can be caused by punctal or canalicular stenosis, stones within the canaliculi (caused by chronic infection), retained punctal plugs within the canaliculi, infection in the sac (dacryocystitis), or nasolacrimal duct obstruction (caused by chronic inflammation that may be related to environmental exposure, nasal inflammation or chronic sinus disease). All of these conditions require surgical repair, often with placement of temporary “stents” that stay in place for a number of months following surgery and can be removed safely and comfortably in clinic.
Tearing can also occur in infants as a result of a developmental abnormality in the tear drainage system. This is a topic unique to young children, and information can be found in our web page on pediatric oculoplastic disorders.
Dr. Kahana is an expert at evaluating and treating the causes of tearing. Dr. Kahana and his team will customize a plan based on your symptoms and exam findings.