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from Luke’s Journal 2020 | Breath of Life | Vol.25 No.2
“Jesus wept.” John 11.35 Did God make the eye? The tear ducts? The tears?
“Jesus wept” is the shortest verse in the Bible. Yet these two words carry much meaning. Jesus shed tears at the death of his close friend Lazarus and shows him to be as much human as you or I. He was “deeply moved” and was not afraid to show emotion, in deep compassion for the family who were grieving.
Known as the “Man of Sorrows”, Jesus had tear ducts and was not afraid to shed tears.
Yet, is there any evidence of design in the humble human tear?
Our tears are made of three main ingredients that are vitally important to our vision. If our tears fail, our eyes dry and if the ducts completely fail, not only is this increasingly painful, but we are not far off the bleak dark world of blindness.
Tears are made of an inner layer of mucin, a sticky material that is secreted from the eye surface directly. The middle layer is a watery film that spreads out between the two oily layers, like a sandwich. This oil water interface guarantees a uniform and comprehensive barrier. The outer layer is oily again and creates a waterproof seal.
These three layers are secreted from three different sources. The lacrimal gland secretes the watery middle layer – the gland channels transporting the fluid via tiny tunnels which end at the very tips of our eyelids. The oily outer layer is secreted by another set of glands which also have dedicated channels pumping oil onto the watery base. The innermost layer is secreted straight onto the eye surface.
“If our tears fail … we are not far off the bleak dark world of blindness.”
Certain design principles are recognisable in our tear production: the laws of physics, biochemistry and engineering.
Here is a short list of 5 examples:
1. The shape and form of the tear ducts echo basic engineering principles with around 50 channels evenly spaced at the edge of each upper eyelid, and 25 evenly spaced on the lower lid.
2. The physical forces created between the oil on water interface ensure a formidable lubricant barrier.
3. The middle watery layer contains around 90 ingredients such as nutrients for the cornea and antioxidants for bacterial repulsion.
4. Given the tears must be transparent for vision, it is impressive that all three layers are see through, and each ingredient is held in balance, teetering on the constant threat of an opaque soup.
5. Without thinking, our blink spreads the oil water smoothly out over the cornea, like a windscreen wiper.
More importantly for us, as human beings, however, is the strange fact that our tears are expressed in response to emotions, such as great happiness or grief. Such tears are quite different from our normal tears, they are dripping with expressions of our soul – output from the deepest parts of our brain. The lacrimal duct alone, is stimulated by three separate nervous stimuli, linked with the brainstem. Yet we weep not automatically, but in response to great stimulus to our mind and soul, at births and deaths. For this reason, Jesus wept.
Dr Iain Johnston graduated from Edinburgh University and completed specialist training in Intensive Care and Anaesthetics in the UK and Australia. Iain works in Intensive Care on the Gold Coast and Tweed Coast with a special interest in acute cardiovascular pathophysiology. In his spare time (!) he represents Australia in the World Medical Football Championship.
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