Eye Health

The anatomy of the eye

Before you can truly understand eye diseases, it helps to learn a little about the eye itself. Despite being small (on average, each eye is around 2.5cm in diameter), it’s one of our most important organs. Our eyes have a lot of working parts and each part has a complex role in helping us see.

How does the eye work?

Our eyes function like tiny cameras, processing light reflected off surfaces to create images. The iris controls the size of the pupil, adjusting the amount of light that enters the eye. In bright light, the iris reduces the pupil size, while in darkness, it enlarges the pupil to let in more light.

Light passes through the cornea and lens, which focus it onto the retina at the back of the eye. The retina analyses colour, intensity, and form, converting these into electric impulses sent to the brain via the optic nerve. The brain then processes these impulses, combining them with our experiences and emotions to create the images we perceive.

The cornea and lens work together to focus light, with the lens dynamically adjusting its shape to help us see objects at varying distances. When light is not perfectly focused, glasses or contact lenses can correct the issue.

Cornea

The clear front ‘window’ of the eye. It continues backward to form the tough outer fibrous coat of the eyeball. Visible at the white part of the eye, this coat is called the sclera.

Iris

The coloured part of the eye that acts as a gatekeeper to control the amount of light entering the eye.

Lens

A clear, specialized protein structure that helps focus images by adjusting the eye's focusing power according to how near or far away an object is.

Vitreous Gel

A clear, specialized protein structure that helps focus images by adjusting the eye's focusing power according to how near or far away an object is.

Ciliary Body

A muscle that changes the shape of the lens to allow for focusing. It’s also a gland that produces a watery fluid called the aqueous humour, which helps maintain the eye's pressure.

Retina

Delicate and finely layered nerve cells lining the inside of the eye. The retina receives light and converts it into electrical signals for transmission to the brain.

Macula

Contains the greatest concentration of light-sensitive cells, called photoreceptors, allowing us to see things in great detail and perceive colour.

Optic Nerve

Formed from all the fine nerve fibres originating from the photoreceptors in the retina. These fibres gather into a bundle and exit the back of the eye, transmitting visual information to the brain.

Want to learn more about the eye? Check out our Eye Health Glossary for more terms.

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Eye diseases and conditions

The eye diseases we work to eliminate are some of the most devastating in the world. We mainly work to reduce the impact of diseases and conditions such as cataract, trachoma, diabetic retinopathy and uncorrected refractive error for which safe and cost-effective ways of preventing vision loss or providing treatment to restore sight are available. However, our work isn’t exclusively on these diseases. Many eye diseases and conditions can be treated or prevented – an incredible injustice when so many millions of people who can’t see, also can’t access help.

Childhood blindness

Many eye diseases in children can lead to permanent blindness if left untreated. This is a significant problem in developing countries because many families don’t have access to basic eye health services. Three out of four children with blindness live in poverty. Research shows a child a minute goes blind, so early intervention is critical.

Clinical outcomes

Eye diseases like cataract, trachoma and diabetic retinopathy can lead to permanent blindness when these conditions are often treatable or preventable. Surgery can improve quality of life and general health. The key to the success of our programs is delivering effective treatment outcomes, where the beneficiary can be productive and independent.

Disclaimer: the content on this page is not intended to be medical advice. For medical advice, please contact your local health professional.