How our eyes see

How eyes work

• Light enters the eye through the cornea (a clear "window" at the front of your eye). The light passes through the cornea and pupil to the lens (located 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 focusing 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, of which there are two types: rods and cones. Rods are responsible for vision in low light conditions (light and dark adaptation), while cones are responsible for vision in bright light conditions, colour vision and detailed vision like that used for reading and 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.

There are many eye conditions which may cause low vision and your eye care professional is your best source of information on your specific condition. Additionally, many conditions often have no symptoms in the initial stages of disease. For this reason, regular eye checks are the best way to preserve sight during all the stages of life.

For more information

• Visit this article to learn out more about low vision. 
• Always speak to your GP and eyecare professional about the best treatment options for you.