Human Eye

The eye is an organ a part of the nervous system made of over 2 million parts that work together to process light and help us interpret shapes, colours and dimensions around us. This guide will take you through the fascinating visual process - which, like a camera, begins when light is captured at the front of the eye, travels through the middle and ends at the back of the eye.

The eye is the primary organ of the visual system; it receives pictures from the person and converts them into an electric signal that travels via the optic nerve to the brain. The visual system is the component of the central nervous system responsible for visual perception, which includes receiving, processing, and interpreting visual information in order to construct a representation of the visual world. The eyes are in charge of sensing light that enters them. The light is then turned into a picture in the brain. Six paired cranial nerves supply sensory and motor innervation to the eyes. These nerves communicate with one another to produce motions, reflexes, and vision.

How light enters the eye

Everything around us is made of surfaces that reflect light in varying wavelengths. These light rays enter through the cornea at the front of the eye and pass freely through the pupil.

Because human eyes are not very good at blocking blue light, virtually all visible blue light travels through the front of the eye (cornea and crystalline lens) and reaches the retina, which contains the cells that turn light into pictures for the brain to analyse.

Move the brightness slider to explore how the eye filters light.

Lens adjusts focus

Next, the light makes its way through the crystalline lens, which bends the rays and flips them back onto the retina, resulting in a reverted image.

The lens, also known as the crystalline lens, is a translucent biconvex structure in the eye that, along with the cornea, serves to focus light on the retina. The eye's crystalline lens is a natural lens that produces one-third of the eye's total optical power and focuses light onto the retina (the light-sensitive tissue at the back of the eye). Because the crystalline lens is elastic, it may bend and change shape. The centre of the convex lens is thicker, while the margins are thinner. A convex lens is present in the human eye. The lens of the eye refracts and focuses light on the retina. Unlike ordinary lenses, the biconvex lens in the eye may change shape. The lens changes shape to vary the focal length of the eye, letting it to concentrate clearly on objects at varied distances. A lens's ability to focus is referred to as accommodation. Hence, the human eye has a convex lens.

Brain interprets the image

Finally, the light rays go through a sharp focusing point of the retina, where they are transformed into electrical signals that reach our brain via the optic nerve.

Because our brains' are so used to seening the world upside-down, our brain actually takes the two images from both of our eyes and creates a new image based on what we see. Pretty cool isn't it?

The half-fallacy "we see everything upside-down" is mostly correct. What actually happens is your brain processes a pattern of nerve impulses to create a useful image based on what you are looking at. Processing visual information takes a lot of our brains' processing power.

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Anatomy of the eye

Click on the buttons to learn about the functionality of the optic nerve, pupil, conjunctiva and other parts of the eye.

Cornea

The clear, dome-shaped front part of the eye that helps your eye focus light, so you can see clearly.

Pupil

The opening in the centre of the iris that controls the amount of light passing through to the back of the eye.

Crystalline Lens

The transparent, elastic structure inside the eye that bends to focus light rays onto the retina.

Aqueous Humour

The clear, watery fluid in the front of the eyeball made up of water, sugars and various nutrients. It nourishes the cornea and the lens and gives the eye its shape.

Iris

The coloured part of the eye surrounding the pupil that controls the amount of light that enters into the eye.

Conjunctiva

A clear, thin transparent layer of tissue that covers part of the front surface of the eye and the inner surface of the eyelids.

Sclera

The dense protective tissue of the eyeball that forms the ‘white’ of your eye. Sclera forms over 80% of the surface area of the eyeball, from the cornea to the optic nerve.

Vitreous Humour

A clear gel-like substance that occupies the space between the crystalline lens and the retina and transmits initial light waves.

Optic Disc (Blind Spot)

A disc on the retina that is the point of entry of the optic nerve. It lacks visual receptors, so it’s also known as the blind spot.

Macula

The central part of the retina that allows us to see fine details.

Fovea

The central part of the macula, necessary for activities where visual detail is important, such as driving or reading.

Retina

The light-sensitive nerve layer that lines the inside of the back of the eye made up of about 130 million cells. It creates electrical signals that travel through the optic nerve to the brain.

Optic nerve

A bundle of nerve fibres that connect the retina with the brain and help us interpret what we see.