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    Sight is one of our senses – it helps us to be aware of our surroundings. The eye contains structures that allow it to perceive light, movement and differences in colour. Eyes are like cameras – they take a picture and then our brains interpret what we see.

    How do eyes work?

    Eyes are designed to take in small amounts of light through the pupil. The pupil opens and closes depending on how much light there is. When it is darker, your pupil will be larger in order to allow more light in. When you look at an object, the light reflected from it enters the eyes through the pupil. The lens in the eye focuses the light and directs it to a small area in the centre of the retina at the back of your eyeball to a part called the macula. The macula is responsible for central detailed vision, allowing you to see fine detail and colour.

    The light coming into your eye stimulates the nerve cells in the retina. This creates messages that are sent along the optic nerve to the brain. The optic nerves from the two eyes join inside the brain. The brain combines the vision from the two eyes allowing you to see one image.

    How do you know your eyes are working properly?

    Vision screening – an eye exam – with an optometrist usually involves several types of tests. The test we are probably most familiar with is the acuity test – when we use one eye at a time to look at letters or symbols from a prescribed distance. Our responses to this test are used to compare each eye’s vision level compared to standard vision. Other tests measure the size and shape of the cornea and our peripheral vision (objects on the sides of our field of vision). 

    Eye conditions, also known as visual impairments, affect people’s ability to see. Two of the most common eye conditions are myopia and hyperopia. Myopia is more commonly known as near-sightedness or short-sightedness. For people with myopia, objects that are close to them look clear but objects that are further away look blurry. People with hyperopia experience the opposite condition – far-sightedness or long-sightedness. Objects that are far away look clear but objects that are close are blurry. Both conditions are due to the shape of the eyeball causing light rays to bend (refract) incorrectly. With myopia, the eyeball is too long and light focuses in front of the retina. With hyperopia, the eyeball is too short and light focuses behind the retina.

    Astigmatism is an eye condition that results in objects appearing blurry when both close up and far away. Astigmatism is caused by an unevenly shaped cornea (the transparent front of the eye) focusing light in two different places. All three of these eye conditions are helped by wearing glasses or other corrective lenses.

    Visual impairment and education

    About 80% of learning at school is dependent on vision. Research shows that children with reduced vision are disadvantaged in literacy and numeracy and that reduced vision can cause poor focus, perseverance and class participation. 

    In Aotearoa New Zealand, there are two opportunities for vision screening. The first is at age 4 and then again at the age of 10–11. The screenings offer limited tests, may not reach all students and have no way of addressing problems that are picked up. 

    The Vision 20/20 Project is a Participatory Science Platform (PSP) project that is working to rectify some of these issues. Experts from Otago Polytechnic and Otago University’s School of Medicine have teamed up with Tahuna Normal Intermediate School to develop a peer-to-peer vision screening programme. Read about the rich learning opportunities this project provides and how it might ultimately benefit students throughout Aotearoa in the article Improving vision screening for children.

    Related content

    Depth perception is the ability to perceive the world in 3D and judge the distance of an object. Find out how this works with human eyes and with 3D glasses.

    The article Ophthalmology research profiles Gordon Sanderson and the roles of ophthalmologists in supporting vision.

    Activity idea

    In the activity Pinhole cameras and eyes, students make a pinhole camera and see images formed on an internal screen. They then use a lens and see brighter and sharper images. This models the human eye and can be modified to demonstrate short-sightedness and long-sightedness.

    Funding

    The Vision 20/20 Project received funding through Otago Science in Action, the Otago pilot of the Participatory Science Platform (PSP) – a programme that is part of the Curious Minds initiative and funded by the Ministry of Business, Innovation and Employment.

    The government’s national strategic plan for Science in Society, A Nation of Curious Minds – He Whenua Hihiri i te Mahara, is a government initiative jointly led by the Ministry of Business, Innovation and Employment, the Ministry of Education and the Office of the Prime Minister’s Chief Science Advisor.

      Published 9 December 2020 Referencing Hub articles