How exactly do my eyes work?

We all know that the eyes are our organs of sight, but what exactly allows us to see clearly? Here, we explain the eye in detail, exploring the functions of each part individually as we uncover the mysteries of the eye.

The eyeball and its functions

The eyeball is the name given to the visible combined elements of the eye. It is a spherical bilateral object roughly the size of a ping pong ball. There are also other elements that we cannot see. Each plays an important part in our vision.

Our eyes see by taking the light that reflects off an object and converting it into electrical energy that is transported to the brain via the optic nerve. Light must travel through several eye tissue layers, each has its own function before our brain is able to interpret an image correctly.

The journey of light

First, light travels through the cornea, which is a clear dome-shaped layer at the front of the eye. The cornea is made up of five fine tissue layers:

1. The epithelium

The outermost corneal layer made up of regenerating cells. Its primary function is to protect the cornea from bacteria and other contaminants.

2. The Bowman’s layer

Another protective layer made of collagen. This one protects the stroma.

3. The stroma

The thickest layer of the cornea. It maintains the curve and clarity of the cornea.

4. Descemet’s membrane

Prevents the stroma and endothelium from meeting.

5. The endothelium

Ensures the water balance of the cornea is correct and the cornea is transparent.

After passing the cornea, light waves travel through a liquid called the aqueous humour, which maintains eye pressure.

Light waves bend and shape in the iris (the coloured bit of the eye). In the centre of the iris is the pupil. This contracts and stretches to adjust the amount of light entering the eye (pupillary light reflex).

Behind the pupil is the disc-shaped, transparent lens. It adjusts its shape to allow us to see objects at different distances. The lens is held by ciliary muscles. These contract to make the lens thicker to see objects up close and expand to relax the lens and make it thinner for further distance focus.

An upside-down image is projected onto the lens before travelling through a gel-like substance called the vitreous humour.

The retina

The retina is a membrane that covers the back of the eye. It is light sensitive and consists of millions of nerve cells called cones and rods. Cones are located in the macula, which is responsible for detailed vision, colour perception and definition as well as seeing in the day. These are found in the centre of the retina. There are three types of cones, each one responds to either red, blue or green light waves.

Rods are used in nighttime vision. These cover the rest of the retina. They are useful for peripheral vision and allow us to see in dim light and detect motion.

Cones and rods collect the light waves and convert them into electrical impulses that travel from the retina (optic nerve) to the brain in milliseconds. Each eye goes through this process simultaneously, sending energy via its own optic nerve to the brain, which combines the two images and projects them correctly.

How exactly do my eyes work?

We all know that the eyes are our organs of sight, but what exactly allows us to see clearly? Here, we explain the eye in detail, exploring the functions of each part individually as we uncover the mysteries of the eye.

The eyeball and its functions

The eyeball is the name given to the visible combined elements of the eye. It is a spherical bilateral object roughly the size of a ping pong ball. There are also other elements that we cannot see. Each plays an important part in our vision.

Our eyes see by taking the light that reflects off an object and converting it into electrical energy that is transported to the brain via the optic nerve. Light must travel through several eye tissue layers, each has its own function before our brain is able to interpret an image correctly.

The journey of light

First, light travels through the cornea, which is a clear dome-shaped layer at the front of the eye. The cornea is made up of five fine tissue layers:

1. The epithelium

The outermost corneal layer made up of regenerating cells. Its primary function is to protect the cornea from bacteria and other contaminants.

2. The Bowman’s layer

Another protective layer made of collagen. This one protects the stroma.

3. The stroma

The thickest layer of the cornea. It maintains the curve and clarity of the cornea.

4. Descemet’s membrane

Prevents the stroma and endothelium from meeting.

5. The endothelium

Ensures the water balance of the cornea is correct and the cornea is transparent.

After passing the cornea, light waves travel through a liquid called the aqueous humour, which maintains eye pressure.

Light waves bend and shape in the iris (the coloured bit of the eye). In the centre of the iris is the pupil. This contracts and stretches to adjust the amount of light entering the eye (pupillary light reflex).

Behind the pupil is the disc-shaped, transparent lens. It adjusts its shape to allow us to see objects at different distances. The lens is held by ciliary muscles. These contract to make the lens thicker to see objects up close and expand to relax the lens and make it thinner for further distance focus.

An upside-down image is projected onto the lens before travelling through a gel-like substance called the vitreous humour.

The retina

The retina is a membrane that covers the back of the eye. It is light sensitive and consists of millions of nerve cells called cones and rods. Cones are located in the macula, which is responsible for detailed vision, colour perception and definition as well as seeing in the day. These are found in the centre of the retina. There are three types of cones, each one responds to either red, blue or green light waves.

Rods are used in nighttime vision. These cover the rest of the retina. They are useful for peripheral vision and allow us to see in dim light and detect motion.

Cones and rods collect the light waves and convert them into electrical impulses that travel from the retina (optic nerve) to the brain in milliseconds. Each eye goes through this process simultaneously, sending energy via its own optic nerve to the brain, which combines the two images and projects them correctly.