How do we see?

Your eyes take in vast amounts of information about what’s around them, sending signals to the brain so you can see shapes, colours, texture and movement. Learn more about how light passes through the eye to the retina and sends signals through the optical nerve, to your brain.

How do we see?

  1. Light reflects off objects and travels in a straight line to your eye.
  2. Light passes through the cornea, the pupil and the lens.
  3. The cornea and lens bend (refract) the light to focus onto the retina.
  4. Photoreceptors on the retina convert the light into electrical impulses.
  5. The electrical impulses are sent along the optic nerve to the brain.
  6. The brain processes the signals to create an image.

The functioning of the eyes

Your eyes play a crucial role in almost everything you do. Here are some of the main functions that help the eye make clear, single images.

Seeing - Eyes take in light and convert it into electrical impulses that are sent to the brain, which processes these signals to form the images we see.

Moving - The six ‘extraocular’ muscles control the movement of the eye. Four move the eyeball up, down, left and right; two adjust the eyes to counterbalance head movement. If your eyes don't move together you will see double.

Blinking - Every time you blink, a salty secretion (basal tears) from your tear gland is swept over the surface of the eye, keeping your eyeballs moist and clean. We really appreciate this in dusty / windy conditions. Tears are also bactericidal so they help prevent infections.

Crying - Tears are salty fluid containing protein, water, mucus and oil – are released from the lacrimal gland in the upper, outer region of the eye. Reflex tears protect the eye from irritants like smoke, dust and wind. Emotional tears are a response to sadness or joy.

Protecting - The eyes are recessed into sockets in the skull to protect them from injury. Eyelashes and eyelids keep out dust and dirt. Eyebrows are arched in shape to divert sweat away from your eyes.


To understand how your eyes work, it's helpful to know about their structure and component parts.

Component Parts

Below are the component parts of the eye and a brief explanation of their role in allowing you to see the world around you.

Sclera - The ‘white’ of the eye that protects the eyeball and gives it it's firm, regular shape.

Pupil - The black hole at the centre of the coloured iris, it allows light through.

Iris - The coloured part of the eye that controls the amount of light passing through the pupil.

Cornea - A transparent dome that protects the iris and pupil. Together with the lens, the cornea bends (refracts) light to focus it onto the back of the eye.

Crystalline lens - A transparent adjustable lens that sits behind the iris. It auto-focuses as things get closer to you.

Retina - This layer on the back of the eye that contains millions of photoreceptors (sensors that convert light into electric impulses). These signals are sent along the optic nerve to the brain, where they are processed to create an image.

Macula - A small spot near the middle of the retina that is responsible for our clearest, sharpest vision and our ability to see colours.

Vitreous humor - A jelly-like substance that fills the back of the eye, giving it form and shape.

Optic nerve - The nerve at the back of the eye that carries signals from the retina to the brain.

Conjunctiva - A thin membrane that gives the outside of the eye protection and helps keep it moist. It lines the inside of the eyelid and the surface of the eyeball.

Aqueous humour - A clear fluid that lies in the space between the iris and the cornea. This maintains eye pressure and gives the front of the eye its rounded shape.

Questions about your eyes?

Ask your nearest optometrist today



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