THE MYSTERY OF TEARS
By Jenny Livanos, Holistic Optometrist
As an optometrist, I discuss tear quality, quantity and function in dry eye and external eye conditions with my patients every day. Tears are secreted mainly from the lacrimal glands in the upper, outer region of the eye and drained by the puncta and lacrimal duct in the opposite corner of the eye; they are moved across the eye through blinking.
There are three types of tears, consisting of different molecules, each serving a different purpose. Tears act as both a delivery and an excretory route for nutrients and metabolic products, and contain substances including mucin, lipids, antibodies, proteins and enzymes suspended in salt water. The specific composition of tears varies from day to day and with your health, with less being produced as we age.
THE THREE TYPES OF TEARS
Basal tears – these continuously moisten and nourish the cornea (the clear front ‘window’ of the eye) with oxygen and nutrients. These tears help keep the cornea clear of debris and smooth out irregularities for better vision. Here the enzyme,lysozyme, fights against any bacterial invasion.
Reflex tears– foreign particles irritate the sensory nerves in the cornea, signalling to the ophthalmic nerve and causing these tears to be produced. Onion vapours, hot or peppery stimuli to the tongue and mouth, bright lights, smoke, wind, coughing and yawning can be triggers. These tears help wash out impurities and contain antibodies to help protect the eyes against infection from these irritants.
Psychogenic tears – these are triggered by strong positive and negative emotions, including pleasure, happiness, stress, anger, sadness and physical pain. The emotion is registered in the limbic system, the emotional centre of the brain, and the endocrine system is then triggered to flush hormones into the tears. These tears have higher levels of protein-based hormones like prolactin, which is more prevalent in women and involved in the stress response; adrenocorticotrophic hormones, which help regulate stress in the body; and leucine-enkephalin, a natural painkiller and mood improver. This removal of extra hormones from the body is part of our emergency response to restore physiological and psychological balance.
WHY DO WE CRY?
Tears produced with emotions seem to be a uniquely human experience; humans appear to be the only species producing these tears for health and as a survival advantage. However, research, including that by famous naturalist, Charles Darwin, has found that elephants can shed tears in grief. Crying may be an evolutionary adaptation to having our needs met. We cry to elicit sympathy and aid from others, to solidify relationships with those around us and to display vulnerability and submission, especially when we are young.
Crying is beneficial to our health and mental well being – most people feel better after a good cry. Psychologists recommend that people express their emotions through talking and crying. If we stifle emotional tears, there may be an elevated risk of heart disease and hypertension – crying makes us less prone to stress-related illnesses. Studies have shown that sufferers of colitis and ulcers tend to have a less positive attitude about crying than healthier people. In Japan crying clubs have been set up to induce a good cry by watching sad movies, TV shows and reading sad books!
MEN AND WOMEN CRY DIFFERENTLY
Men and women shed different kinds and amounts oftears, owing to biological and cultural reasons. Women are physically wired to cry more tears than men. Men have smaller tear glands and gland cells, so produce less tears at any one time. The male tear duct is larger than the female’s, so will hold more tears – a woman’s tears will spill out quicker! In men, testosterone helps raise the threshold between the emotional stimulus and the shedding of tears, so men tend to take longer to cry.
According to the German Society of Ophthalmology, women cry between 30 and 64 times per year, while men cry 6 – 17 times per year. Women cry for six minutes and more loudly, with a higher chance of sobbing, whereas men cry for 2 – 4 minutes. Men tend to cry over more serious matters than do women. As men get older, they become less angry and tend to cry more, whereas women experience the opposite – this is mainly due to the decline in testosterone in men and oestrogen in women.
Chemicals in emotional tears alert others to emotional or physical distress and can decrease men’s libido.An experiment by Weizmann Institute researchers tested male volunteers and found that after smelling odourless tears, they were less responsive to an attractive face.
A photographer named Rose-Lynn Fisher has recently found differences in the appearance and composition of tears under the microscope, depending on the emotion and its trigger. During a stressful period in her life, she decided to examine her own tears and those of volunteers, totalling 100 different types of tears. As tears are suspended in salt, they form very interesting patterns when they crystallise. Tears from onion-chopping, happiness, sorrow and grief all appeared different under the microscope.
Current research has indicated that biomarkers like proteins in tears can confirm different eye diseases. Also being studied are tear biomarkers for the early detection of systemic diseases, including genetic disorders, infectious diseases, diabetes and even cancer.
Tears are truly mysterious.As Antoine de Saint-Exupery wrote in his book,The Little Prince, “It is such a secret place, the land of tears”!