Sadness, joy, a moving scene in a romantic movie, rolling laughter or just peeling an onion – tears are part of everyone's life, and although they are often referred to as just drops of salt water – they really are not what they are. We used ChatGPT to summarize everything you need to know about tears.
According to Danielle Oring, assistant professor of optometry at the University of Plymouth in the UK, tears come in three distinct strains, each with its own unique composition and purpose, providing insights into the complexity of our emotional and physiological responses.
The first, and most familiar, type is emotional tears, which fall in moments of sadness or happiness, and effectively express our deepest feelings by crying. They have a high content of stress hormones and are believed to be designed to remove these hormones from the body.
The second type is tears designed to cleanse, lubricate and nourish the delicate tissues of the eye. These tears contain salt ions, electrolytes, and proteins with antimicrobial properties that protect the eye from possible damage.
The third type is reflex tears, triggered by irritants, such as smoke or harsh compounds released when cutting onions. Reflex tears are the body's response to discomfort. They contain more water than other tears, with lower levels of fats and proteins.
The eye's tear film, into which tears are secreted, includes three layers: an oily outer layer that keeps the cornea moist (the transparent front of the eye), an aqueous intermediate layer that provides lubrication and includes proteins, oxygen and electrolytes, and right on the cornea is the inner layer composed mainly of mucin, a mucous protein that ensures that the tear film remains close to the eye.
Oring finds that people typically produce between 1.4 and 5.8 ml of tears a day—most of the kind designed to lubricate and maintain the eye. However, various factors can affect tear production. Activities like cycling can increase tear evaporation, changing production rates. In contrast, tear production decreases in vapor environments, where extra moisture is unnecessary.
For many people, tear balance is not normal enough, leading to dry eyes. Many factors contribute to this condition, including smoking, poor diet, and excessive screen time without blinking enough. As age progresses, tear gland function declines, increasing susceptibility to dry eyes. Conditions like Sjogren's syndrome – a disorder that causes the immune system to attack the glands responsible for moistening the eye – can exacerbate the problem and make it difficult to produce all types of tears, leaving the eyes dry.
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