How our eyes see

Our eyes are complex organs that allow us to see the world around us. We’ve simplified an explanation of how they work:

• Light enters the eye through the cornea (clear window at the front of your eye). The cornea focuses the light entering the eye onto the lens inside the eye (behind the iris).
• The iris (the coloured part of the eye) adjusts the size of the pupil, controlling the amount of light that enters the eye.
• The light then passes through the lens, which further focuses it onto the retina at the back of the eye. Your lens is responsible for focusing the light from objects at different distances, a bit like the focus function on a camera or binoculars.
• The retina is the sensory layer at the back of the eye responsible for receiving the light image and converting it to electrical impulses to send to your brain. The retina contains millions of light-sensitive cells called photoreceptors, which are of two types: rods and cones. Rods are responsible for vision in low light conditions (light and dark adaptation), while cones are responsible for colour vision and detailed vision like reading or seeing facial features.
• When light reaches the photoceptor cells, it triggers chemical changes that create electrical signals.
• These signals are then transmitted through the optic nerve to the brain.
• In the brain, the signals are processed and interpreted, allowing us to perceive the visual information as images.

All these steps need to happen in perfect balance for humans to have clarity of vision, peripheral vision, colour perception, and the ability to adapt to different lighting levels.

Many things can disrupt the visual process which can lead to needing to wear glasses or create a situation where a person experiences vision loss. Vision loss could occur because the eye is not seeing as it should, or the brain is not properly receiving images.