-The EYE Digest-
A Sob Story – The Three Types of Tears
Ok. Pause for a second and put yourself in three different scenarios:
Scenario 1: You are in the midst of watching a truly depressingmovie. Maybe it's Schindler's List or The Notebook. You cannot help it. You've mustered the strength and resolve, but it just will not do. Waterworks start. You are crying from watching a sad movie.
Scenario 2: It is 4 pm. You are at work still staring at that darn computer screen that shows miles and miles of spreadsheet numbers and cells. A few more hours left. Wait a minute. Your eyes are watering. It's been a long workday and to top it off, you're crying.
Scenario 3: You are about to make the greatest beef stew ever. Or so the recipe book says. Next ingredient called for: chopped onions. Knife, check. Cutting board, check. Onions, check. Crying eyes, check.
What is the unifying theme behind the three unpleasant (or pleasant for a very select few) scenarios presented? Well the obvious: crying, and the byproduct, tears. Now for the interesting part. Did you know that the tears produced in each scenario are different? While all tears contain water, lipids, lysozyme, lipocalin, glucose, and sodium; the composition differs drastically. In fact, there are three categories of tear type produced by the lacrimal glands which closely mirror the scenarios we previously described.
Tear #1: Psychic Tears
No, these tears don't possess a crystal ball and tell you your future. Rather, these tears are associated with emotions, specifically happiness, pleasure, stress, and sadness.
But why do we cry when we become overwhelmed with emotion? There might be a variety of reasons.
A couple studies have found that stress hormones are actually released through Psychic Tears. This may be the reason that they help cause relief when produced during an emotionally stressful situation.
When looking at the evolutionary nature of crying, it may have developed to show vulnerability and even submission to ensuing attack, thus causing the attacker to change their course of action.
Finally, psychologists have looked at crying as a way to develop social input with others. Viewing an individual cry allows another to collaborate and further understand that individual’s feelings in a more substantial way. Thus, crying may be used to strengthen social bonds.
Tears #2: Basal Tears
No clever joke for this one. Basal tears represent your basic functional tear. They are produced in order to lubricate and the cornea. Lubrication of the cornea, along with a tear film of healthy volume are vital to ensure good visual acuity and comfort. Basal tears also present an immunological barrier to the outside world.
Tear #3: Reflex Tears
Reflex tears, much as their name suggests, are produced in response to a stimuli or irritant. Examples of such are onions, spices, smoke or tear gas. Additionally, reflex tears can be created in response to environmental insults such as wind gusts, bright lights, or a sudden drying of climate.
Reflex tears are produced via a pathway were corneal nerves message the brain stem a signal of distress. The brain stem then sends hormonal messengers to the lacrimal glands, causing tears to form.
As with Basal Tears, the ultimate goal of Reflex tearing is to protect the eye.
In conclusion, at the basic level, tears are an essential substance created by the body to ensure a healthy eye and vision. Tears can also serve other purposes such as reacting to an external stimuli or in response to a certain emotional feeling. So next time you cry your eyes out, remember what is really going on, it might make that cry a little easier.
-Dr. Aaron Neufeld
Dr. Aaron Neufeld is the Chief Optometrist at Los Altos Optometric Group and primary author and editor of The EYE Digest.
Contact him with questions or ideas for future articles at (650) 948-3700 or firstname.lastname@example.org