The lens is a clear disc-like structure that helps to focus light on the retina. It can do this because it is adjustable, and uses a muscle called the ciliary muscle to change shape and help us focus on objects at different distances. The automatic focusing of the lens is a reflex response and is not controlled by the brain.
Once the image is clearly focused on the sensitive part of the retina, energy in the light that makes up that image creates an electrical signal. Nerve impulses can then carry information about that image to the brain through the optic nerve.
Other parts of the eye include the aqueous humour, a liquid which sits in a chamber behind the cornea, and the vitreous humour, the clear gel that fills the space between the lens and the retina. The sclera is the white part of the eye, forming an outer layer that protects everything inside, while the choroid is the layer of the eye that lies between the retina and the sclera. It is made up of layers of blood vessels that nourish the back of the eye.
For more than 60 years, Sightsavers has been working with partners to prevent or treat these and other causes of avoidable blindness that affect hundreds of millions of people in developing countries. We do this not only by distributing treatment and carrying out operations to restore sight, but also by strengthening health systems to enable more people to access eye health services, and treatment and operation programmes, into the future.
You can find out more about what we do, or support Sightsavers’ work and help people to see again by making a donation.