Sight is a team effort between the brain and our eyes. This fascinating process for observing our environment is something most of us take for granted every day of our lives. Many people wear prescriptions glasses or contact lenses without understanding how these things enhance eyesight.

In simplest terms, sight is the process by which our brains make sense of light, but just how it all comes together is a bit more complicated–and supremely fascinating.

The players

Before we really dig in, here’s a brief rundown of the pieces of the eye and what they do.

  • Retina

The collection of light-sensitive cells at the back of the eye.

  • Lens

The lens sits behind your iris. It actually changes shape to best filter light signals.

  • Iris

The colored part of your eye that encompasses the pupil. The iris is actually a circular muscle and it can control how much light reaches the retina.

  • Cornea

A clear layer in the front of the eye that works with the lens to allow light to enter the eye.

  • Optic nerve

The optic nerve channels communication between the retina and the brain, essentially allowing the brain access to the information “seen” by the eye.

The steps to sight

The only thing we can truly see is light. Where there is no light, there is nothing for the eyes to see. Light bounces off things in the environment and then makes its way to our eyes. Color is perceived by the stimulation of cones (humans have red, green and blue cones). The more cones a species has in its eyes, the more colors it can see. This is why some creatures (such as the all-seeing mantis shrimp) see a wider variety of colors than others.

When light hits our eyes, our irises either constrict or dilate our pupils to let in less or more light respectively. When your pupils appear bigger or smaller, it’s actually the fault of your irises. Your irises will let more light in to help you see better in darker environments, and they will prevent damaging amounts of light from entering on brighter days. This is why wearing sunglasses that don’t filter UV rays can actually be harmful. They trick your irises into dilating your pupils and thus letting in more UV rays than they would have had you worn no sunglasses at all.

Light passes through the lens of the eye, which will refocus the light before it reaches the retina. It is this step, the focusing of light on its way to the retina, that often happens less than perfectly. If the eye is not properly focusing light, prescription eyeglasses become necessary for clear sight. Eyeglasses help bend light to compensate for imperfections in the eye’s natural processes.

Light becomes an electrical impulse

The brain cannot “read” light as it is. The retina translates re-focussed light into electrical impulses that the brain can comprehend. These electrical impulses travel along the optic nerve to the back of the brain, where they are decoded into images.

All this happens in an instant, giving us the illusion of seeing things in real time. But in reality, we see everything with a slight lag. It takes time for our brains to process the light entering our eyes, and light itself takes time to travel to us. So the next time someone tells you to stop living in the past, you can tell them that it’s physically impossible!

When your eyes and brain disagree

The more literal aspect of sight is handled by your eyes themselves, but the interpretation of all this data is handled by your brain. And sometimes your brain has other ideas. It’s not unheard of for your brain and eyes to “not see eye to eye”. While our eyes absorb light, it’s ultimately up to our brains to make sense of everything.

For centuries, people have been willingly exploring this relationship between brain and eyes by playing with inverted glasses and optical illusions. A perhaps more alarming example is known as the stopped clock illusion, where our brain fills in significant portions of our day with “sights” that we didn’t truly witness.

And that’s to say nothing of the phenomenon known as blindsight.

A classic optical illusion

Protect your eyesight

Healthy eyesight is the result of complicated collaboration between your brain and various parts of your eyes. Damage to any one component could severely damage your vision. The good news is that the majority of vision loss, both age related and that which is the result of damage, can be avoided.

Regular eye exams are crucial to maintaining eye health. Your optometrist will be able to spot many problems before you do, and can administer prompt treatment. Your eye doctor will also be able to update your prescription to adjust for any changes your eyes may have undergone. Having an up-to-date prescription allows you to buy prescription glasses online, saving money and time.

Prevention is key to avoiding most eye issues. Practice good contact lens hygiene and protect your eyesight from the sun with 100 percent UV protection prescription sunglasses from