Tears are commonly associated with the expression of our emotions, such as joy or sadness. They are also essential for protecting our eyes and keeping them correctly hydrated.
Our eyes produce from 56 to113 litres of tears each year. A feeling of joy or sadness, an external event that may irritate our eyes can all trigger them.
What are tears, exactly?
Tears are essential to maintain the health of our eyes. Not only do they keep them hydrated, helping us to see clearly, they also help communicate emotions and feelings.
There are three types of tears:
- Basal tears are in our eyes all the time. They lubricate, nourish and protect the cornea, providing a shield against dirt, dust or debris;
- Reflex tears are formed when our eyes need to wash away any harmful irritants, such as smoke, foreign bodies or onion fumes (that’s why we weep when chopping onions!). These tears can contain higher levels of antibodies than basal tears, since they help fight bacteria and other microorganisms;
- Emotional tears are produced in response to emotions and can appear as a reaction to joy, sadness or fear. Some scientists agree that emotional tears contain hormones and proteins that are not present in the other types of tears.
What are tears made of? Where are they produced?
Tears have a composition similar to saliva and contain enzymes, lipids, metabolites, and electrolytes. Every tear is made up of three layers: an inner mucous layer that keeps the tear attached to the eye; a watery middle layer, that keeps the eye hydrated, repels bacteria and protects the cornea; an outer oily layer that keeps the surface of the tear smooth for the eye to see clearly, and prevents the other layers from evaporating.
Tears are produced by lacrimal glands, which are inside our eyes.
Tears are spread across the surface of the eyes when we blink, then they drain inside tiny holes in the corners of our upper and lower eyelids, travelling through small canals that end inside our nose, where they will either evaporate or be reabsorbed.
When too many tears are produced, they overwhelm the lacrimal draining system and spill out of our eyes, rolling down our cheeks when we weep.
Tear production slows with age, hence the possibility for elderly people to develop the dry eye syndrome. Wearing contact lenses or using certain medications can also cause dry eye.
However, it is important to remember that dry eye can be a symptom of other eye conditions, such as blepharitis. In this case, seeing an ophthalmologist is highly recommended.