To celebrate world sight day (9 October 2025), we thought we’d share some fascinating facts about sight and vision that will blow your mind! If you want more insights around the science, we have a list of sources/citations at the end of the blog.
The science of sight
Sight is incredibly complex, and while we still don’t know half as much as we’d like about the eye and how our brains process visual information, scientists uncover something new and fascinating about our vision every day. We thought we’d share some of these intriguing and mind-blowing discoveries you can share at your next family gathering.
Your Brain fills in Blind Spots
Although each eye has a blind spot where it attaches to the optic nerve, your brain fills in those blanks seamlessly so as not to confuse you. The same goes for your peripheral vision. Since it has incredibly low resolution, your brain compensates by approximating what you’re seeing. Or, in other words, your brain is making up what it thinks you should see.
Red Eye vs White Eye
You can technically see your blind spots through flash photography. Most of us know about ‘red eye’ which is when your eyes show a red ‘light’ in photographs. That is due to the blood vessels and photoreceptors in the retina absorbing most light and only returning ‘reddish’ light. But you may see ‘white eye’ as well – which appears similar to red eye, but is far lighter and brighter. This is where your blind spot is found. Since there are no photoreceptors or light absorption, all light is simply reflected back to the camera.
Your Peripheral Vision helps you Balance
Scientific studies have shown that people who wear goggles that obstruct their peripheral vision find it harder to balance and perform in athletic scenarios. The same is true for people who wear sunglasses that have a blue tint.
Women have Better Eyesight
Scientists believe that up to 12% of women could have tetrachromacy, while one study indicates that up to 50% of women and 8% of men could possibly have this super vision.
Most humans have only three types of cone cells, making them trichromats, but tetrachromacy ups the ante: allowing those with four cone cells to see 100 million colour variations compared to the normal 1-10 million.
Corneas have no blood vessels
The cornea is the only human tissue in the body that has no blood vessels since they would ‘cloud your vision’ and prevent your eyes from properly refracting light.
You’re Temporarily Blind for much of your Waking hours
During your waking hours, your eyes are shut 10% of the time due to blinking. Additionally, you’re ‘temporarily blind’ at least 3-4 times per second due to rapid eye movement. This is called saccades, which are rapid, conjugate eye movements that shift the center of your gaze between visual fields. Saccades take around 200 milliseconds to initiate and occur at 700% the speed of normal eye movement. They’re described as ‘ballistic’ since the movement is predetermined at the onset, but uncontrolled after they start – so you can’t stop your eye from doing it once it’s started.
Saccades make you lose Staring Contests
While we pressume that we lose staring contests due to blinking, the actual fact is that saccades prevent us from maintaining fixation on any single thing. So although you can’t really see saccade taking place in another person, the fact of the matter is that your eyes perform these rapid movements in milliseconds without you even noticing. These are called microsaccades – which alter eye movements by 10 degrees per second.
Saccades serve a Great Purpose
The rapid movement of saccades allow you to take in more of your surroundings than the object or thing you’re focusing in. Essentially it helps you paint a colourful picture of your surroundings and environment, even though you believe you’re only looking at a certain area.
Around 2% of the population see ‘things’ as colours
Charles Bonnet Syndrome presents as complex visual-olfactory hallucinations which is particularly prevalent in people who can’t see. At first believed to be a type of psychosis, scientific studies found that this syndrome occurs due to denervation sensitivity. Essentially the loss of neuronal input from normal visual stimuli ‘releases’ electrical impulses in the brain that signal and synampse in the visual cortex of the brain. This also extends to odors – where blind people can see colours while smelling scents.
Reading Braille activates the Visual Cortex
Although Braille is read through touch, scientists have discovered that the visual cortex lights up when blind people read Braille. More interesting is that these areas are far more active in individuals with early-onset blindness than those who become blind later in life.
Vision consumes Loads of Energy
Despite comprising merely 2% of total body weight, the brain consumes nearly 20% of the body’s oxygen and 33% of the body’s glucose. Of this oxygen and glucose consumption, up to 50% is dedicated exclusively to the visual cortex. But that’s not all. The retina itself consumes more energy than the brain itself.
Want some more interesting facts?
We’ll be sharing more interesting facts, stats and quirky content around vision, visual impairment and human senses in coming weeks, so keep an eye on our social channels and website for more.
Get in touch…
If you have suggestions or feedback on our blog articles, feel free to mail us on: connected@heinwagneracademy.org
Sources:
- Anon. Experiments with the blind spot and filling in. Nivea. Available at: http://nivea.psycho.univ-paris5.fr/FeelingSupplements/BlindSpotFillingInExperiments.htm
- Anon. Your Amazing Eyes. National Geographic Kids. Available at: https://www.natgeokids.com/nz/discover/science/general-science/human-eye/
- Young, E. (2020) Seven strange quirks of human vision. The British Psychological Society. Available at: https://www.bps.org.uk/research-digest/seven-strange-quirks-human-vision
- Othman B.A., Somani A.N., Lee A.G., Kini A., and Al-Zubidi N. (2025) Saccade. American Academy of Ophthalmology. Available at: https://eyewiki.org/Saccade
- Peralta S. (2023) Tetrachromacy: Superhuman vision? All About Vision. Available at: https://www.allaboutvision.com/eye-care/eye-anatomy/tetrachromacy/
- Macdonald F. (2016) Scientists have found a woman whose eyes have a whole new type of colour receptor. Science alert. Available at: https://www.sciencealert.com/scientists-have-found-a-woman-whose-eyes-have-a-whole-new-type-of-colour-receptor
- Gubernick D., Ameli P., Teng Q., Velez A., Heilman K.M., and Hedna V.S. (2014) Visual-olfactory hallucinatory synesthesia: The Charles Bonnet Syndrome with olfactory hallucinations. Elsevier. Cortex 30 (2014) 204-207.
- Weiss P.H., and Fink G.R. (2009) Grapheme-colour synaesthetes show increased grey matter volumes of parietal and fusiform cortex. BRAIN: A Journal of Neurology. 2009: 132; 65-70. doi:10.1093/brain/awn304
- Hurton B. (2003) Visual Cortex Activity in Early and Late Blind People. The Journal of Neuroscience, May 15, 2003 • 23(10):4005– 4011 • 4005
- Wong-Riley M. (2010) Energy Metabolism of the Visual System. Dove Press Journal: Eye and Brain. 22 July 2010:2 99-116