Parts of the Eye
- Cornea: The cornea is the transparent outer layer of the eye that refracts, or redirects, light to a sharp focus at the retina.
- Lens: The lens is a transparent structure inside the eye that works with the cornea to focus. It fine-tunes images and allows us to see at various distances.
- Iris: The iris is the visible outer layer that gives us our eye colour. It adjusts the size of the pupil, determining how much light reaches the retina.
- Pupil: The pupil is the hole in the centre of the eye that lets light in. It gets smaller in bright conditions to let less light in and bigger in dark conditions to let more light in.
- Retina: The retina is a light-sensitive tissue that lines the back of the eye. It consists of rod and cone cells. These cells collect the light signals directed onto them and send them as electrical signals to the optic nerve at the back of our eye.
- Macula: The macula is the central part of the retina that allows us to achieve high-quality vision and accounts for our ability to read, to drive safely and to see the world in detail and colour. The macula is yellow due to the collection of pigment from coloured fruit and vegetables we eat as part of our daily diet.
- Fovea: The fovea is the centre of the macula which provides the sharp vision.
- Rod Cells: Rod cells are concentrated around the edge of the retina. They help us to see things that aren’t directly in front of us, giving us a rough idea of what is around us. They help us with our mobility and getting around, by stopping us from bumping into things. They also enable us to see things in dim light and to see movement.
- Cone Cells: Cone cells are concentrated in the centre of our retina where the light is focused by the cornea and lens. This area is called the macula. Cone cells give us our detailed vision which we use when reading and looking at people’s faces. They are also responsible for most of our colour vision.
- Retinal Pigment Epithelium (RPE): The retinal pigment epithelium is a layer of cells located just outside the retina and is attached to the choroid.
- Choroid: The choroid is a layer containing blood vessels that lines the back of the eye; it is located between the retina and the sclera.
- Sclera: The sclera is the white outer coat of the eye, surrounding the iris.
- Optic Nerve: The optic nerve carries information about what you see from the retina to the brain.
- Vitreous: The clear, jelly-like substance found in the middle of the eye that helps to regulate eye pressure and shape.
The Spectrum of Sight Loss
Most people who have a visual impairment are able to see something. The level of vision can vary from being able to distinguish between light and dark, to seeing large objects and shapes, to seeing everything but as a blur. Visual impairment is a term used to describe all levels of vision loss. It covers moderate sight loss, severe sight loss and blindness. People are not either sighted or blind; there are different degrees of vision loss and different ways in which it can affect what a person sees. For example, some conditions can affect the peripheral vision, and others can affect the central vision. Vision loss can affect people of all ages and can have an impact on all aspects of a person’s life: social, school and work, and everyday tasks.