Understanding How Your Eyes Work
Eyesight is the most important way that we learn about the world around us. Eyes capture shapes and colours and are responsible for about 75% of what we perceive.
Eyes are designed to respond to light and can sense about ten million different shades of colour. With a direct link to the brain, they gather up to a billion pieces of information each second.
Components of Your Eyes
- Cornea: The cornea is the clear front window of the eye. It allows light to enter the eye. The cornea takes light rays and bends them into the eye, providing about 60% of the eye’s total focusing power.
- Sclera: The sclera is the sturdy white tissue that forms the outer wall of most of the eye.
- Iris: The iris is located behind the cornea — it is the part that gives colour to the eye. The iris is a ring of muscles with an opening in the centre called the pupil (the black centre of the eye). The iris changes the size of the pupil to control the amount of light entering the eye.
- Lens: The lens is suspended directly behind the pupil by tiny elastic-like strands. The lens fine focuses the light that passes through it and provides about 40% of the eye’s focusing power. The lens also serves to block some harmful ultraviolet light rays from entering the inner eye.
- Retina: The retina is a direct extension of the brain. It is a delicate membrane that lines the back inside wall of the eye. The retina catches rays of light that enter the eye and change the images into electrical impulses. These impulses are sent to the brain..
- Optic Nerve: The optic nerve connects the back of the eye with the brain where visual signals are interpreted. The optic nerve carries the electrical impulses from the retina to the brain.
- The Eyelids: The Eyelids protect the eye and block out light when the eyes are closed. Blinking spreads lubrication (tears) over the eye.
From Light to Sight
When the eye is open, light passes through the cornea. The cornea takes a wide spectrum of light and bends it through the pupil to the lens. Signalled by the brain, the lens adjusts its thickness to fine focus the light onto the retina. The photoreceptors catch the light images and encode them into electrical messages, which are sent to the brain by the optic nerve. The brain decodes the impulses and vision becomes a vivid reality.
