Updated 14 September 2015

Secrets of the eyes

There's a lot more to vision than meets the eye.


Think of the mesmerising effect of watching flames in a hearth or the waves of the ocean as they crash to the shore. What we observe with our eyes has a profound effect on our emotions.

Our eyes are also the windows to our souls, through which we portray our feelings to those around us. Glaring at someone most often reveals envy, and is associated with a small pupil size. But when you look into the eyes of someone you love, your pupils dilate – an action that's linked to a positive association with the person.

So, often without realising it your eyes subtly hint at whether you like someone, or not.

Note the difference a dilated pupil size makes to the appearance of this model. Interestingly, it's possible to learn how to control your pupil size. (Image: iStock)

Even though, evolutionarily speaking, vision was the last of our senses to develop fully, it's hard to imagine a world without it. It influences our perceptions and language. What would you imagine a pink flower to look like if you've never seen one before? You'll be able to touch and smell it, even taste it – thereby forming a vague picture of the flower in your mind – but you won't know what "pink" really means, unless you've seen it before.

While human eyes aren't as sharp as those of hawks, we've masterfully managed to extend our vision to compensate for the limitations of our eyes. With the help of telescopes and microscopes, we can now watch stars being born and white blood cells attack viruses and bacteria.

How the eyes work

The eyes are pingpong ball-sized extensions of the brain. Whether hazel-coloured or bright blue, normal eyes function in exactly the same way and are remarkably complex. The optic nerve, for example, has 18 times more nerve endings than the cochlear nerve of the ear.

The different parts of the eye – that's the optic nerve, sclera (the white part), retina, lens, iris (the coloured part), pupil and cornea – all work together to help us observe the colour spectrum.

The eye functions like a small camera by focusing light onto the light-sensitive retina, which contains cells called cones and rods. When light reaches these specialised cells, they convert the light information into an electric signal that's relayed to the brain by means of the optic nerve.

With normal vision, both eyes aim at the same spot. The brain then fuses the two pictures into a single, three-dimensional image, which gives us depth perception.

Disease diagnosis through the eyes

Could the eyes be more than a sense with which to observe the world or communicate emotion? In complementary and alternative medicine, our amazing blinkers are also used to diagnose disease.

Iridology is a complementary-therapy technique based on the belief that patterns, colours, markings and other characteristics of the iris contain information about our state of health. It isn't a treatment, but a diagnostic tool, used to identify problem areas in the body.

A practitioner will examine your eyes, either by inspecting them with a regular magnifying glass and light, or more advanced methods, such as state-of-the-art digital photography of the iris. The colour, markings or flecks in the iris area are noted, and then compared to an iridology chart, which relates various spots on the eye to about 50 parts of the body. For instance, the innermost circle in both eyes is said to reflect the health of the stomach.

But iridology is somewhat controversial and there still isn't conclusive evidence that the method really works. But the idea that our eyes act as a map of our organs, and their state of health, certainly is intriguing.

Take good care of your eyes

Since the eyes are an extension of the brain, they're extremely vulnerable to injury, bacteria, viruses and the deterioration of their internal structures. This can lead to loss or weakening of eyesight, and even to systemic illnesses.

Here's how to take good care of your eyes:

1. Have your vision checked regularly. If you're short-sighted by more than -4.00 D (check your prescription), have a yearly retinal check done by your ophthalmologist.

2. Keep chronic diseases, including diabetes and hypertension, under control.

3. Treat the following symptoms as emergencies: sudden loss of vision in one eye, sudden blurry vision or blocked-out spots, persistent flashes of light on the edge of your field of vision, coloured haloes around lights with eye pain and loss of vision, double vision, or eye pain when looking into bright light.

4. Wear sunglasses protecting your eyes against ultraviolet A and B rays.

5. Eat foods rich in vitamin A and beta-carotene, such as cooked carrots, butternut, hubbard squash, sweet potato, tomatoes and green leafy vegetables.

(Carine Visagie, Health24 updated October 2012)

- Gene therapy has lasting benefits. Health24 story originally from Gene Emery/Reuters Health. August 2009.
- Downcast eyes: The Denigration of Vision in Twentieth Century French. By Martin Jay.


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