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Vision is so fundamental to the human experience that sometimes we take our eyes for granted. The human eye is a highly complex organ that provides us with the ability to experience the world in ways that our other senses cannot. Even though we use our eyes during the majority of our waking hours, there are a number of fun and interesting things you may not have realised about your eyes and how they function.
1. The Eyes Perceive Things Upside Down.
What we see are made up of light reflected from the objects and scenes we look at. However, because the cornea at the front of the eye is curved, it bends the light as it enters eye, meaning the image is upside down when it hits the retina at the back of the eye. When the brain interprets the image it turns it back the right way up so we see the world correctly. In an experiment in the 1950s, Austrian Professor Theodor Erismann asked his assistant Ivo Kohler to wear a pair of goggles that made him see upside down. Fascinatingly, Kohler’s brain adapted and he began to see the world rightside-up through the goggles within about a week. The landmark study is still widely referenced today, such as in the work Sachse et al. on Visual perception in 2017.
2. There are Many Protective Features Around the Eye.
Our skull and facial features have evolved over millions of years to protect the fragile eyeball. The socket itself is depressed into the skull, thereby protecting half the eye with bone. Eyebrows are there to catch sweat from the forehead and divert it away from the eyes. Eyelids close to shield the eye from light and particles when needed. Eyelashes create a filter for dust and other particles but also act like the whiskers of a cat or mouse, by sensing when something is close to the eye and triggering the eyelid to close. The entire length of all the eyelashes shed by a human in their life is over 98 feet with each eyelash having a life span of about 5 months. Despite these elements, the eye is still one of our most fragile organs, especially in the face of modern hazards like artificial light and industrial substances. Evolution has not caught up with these new hazards, so eye protection is crucial in these modern environments.
3. Red-Eye in Photos is Due to Blood Vessels in the Eye.
Ever wondered why eyes sometimes appear red in photos? The “red-eye” effect occurs when the light of a camera flash or other bright light source is reflected back at the camera. The reflected light illuminates the blood vessels of the connective tissue at the back of the eye, which produces the red color you see in photos.
4. Iris Scans Are More Secure than Fingerprints.
Like a fingerprint, the iris is unique to each individual; unlike corresponding fingers on each hand the iris in each of our eyes are also different from one another. Our irises have over 256 unique characteristics, compared that to fingerprints that only have about 40. This makes iris scan for biometric systems much more secure than fingerprints.
5. Your Eyes Can Get Sunburned.
Sunburn of the skin is now well understood but did you know you can also get sunburn of the eye. The condition is called photokeratitis and can cause pain, redness, blurriness, tearing, swelling and sensitivity to light. Just like how your skin can peel after sunburn, photokeratitis can lead to the corneal epithelium “sloughing off”. Effects can be felt long after exposure, so always wear good sunglasses when in the sun.
The End in Sight Better understanding the complex nature of our eyes can help us appreciate how lucky we are to have them and how important vision is to the evolution of our species. Understanding our eyes can also help us appreciate how fragile they are so we might better protect them from injury and deterioration. To make sure we keep our eyes healthy and safe from harm we must limit their exposure to light, heat and particles such as dust, by protecting them with quality glasses we can enjoy all the benefits of vision but without the risk.
