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.
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 — due to the blood vessels and photoreceptors in the retina absorbing most light and only returning reddish light. But you may also see “white eye” — which 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 with a blue tint.
Women May 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 (trichromats), but tetrachromacy allows 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 — 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 called saccades — rapid, conjugate eye movements that shift the centre 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.
Saccades Make You Lose Staring Contests
While we presume we lose staring contests due to blinking, the actual fact is that saccades prevent us from maintaining fixation on any single thing. Microsaccades alter eye movements by 10 degrees per second.
Around 2% of the Population See Things as Colours
Charles Bonnet Syndrome presents as complex visual hallucinations, particularly prevalent in people who can’t see. The loss of neuronal input from normal visual stimuli “releases” electrical impulses in the brain that signal in the visual cortex. This also extends to odours — 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 — 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 its glucose — and up to 50% of that is dedicated exclusively to the visual cortex. The retina itself consumes more energy than the brain.
We’ll be sharing more interesting facts, stats and quirky content around vision, visual impairment and human senses in coming weeks. Get in touch at [email protected] with suggestions or feedback.