Definitions

The following contains definitions of the terms commonly used in this web site. However it is important to note that some of these words are sometimes used differently in other literature.

It is important to be able to identify people who have impaired vision. In some eye conditions vision can be improved with spectacles, by an operation or with treatment. If possible, all people with impaired vision should be referred to an eye specialist (ophthalmologist or optometrist) to check if the condition can be treated or vision improved. If after treatment, the person still has low vision, they might need spectacles or special training or equipment so that they can join in activities in the home, school and community.

"Normal" vision
A person is able to perform all close and distant visual tasks that are normally expected in his community. Refractive correction (e.g. glasses) may be needed to give 'normal' vision. A person with 'normal' vision is someone who has between 6/6 and 6/12 (20/20 and 20/40) vision. This means that a letter designed on an eye chart to be seen at 6 metres (20 feet) can be seen at 6 metres in both eyes.

More information on measuring visual acuity can be found in the Vision Screening chapter

Vision impairment
It is the reduced vision caused by eye disease, accident or eye condition present from birth. Some conditions can be treated or corrected to improve vision. Most people (about 80%) who are vision impaired have some vision, that is, they have low vision.

Low vision
Low Vision is significantly reduced vision, that is, visual acuity is less (worse) than 6/18 (20/60) in the better eye or visual fields are less than 20 degrees in diameter. After treatment or with refractive correction (glasses or lenses), vision cannot be corrected to "normal". Visual performance may be affected. A person with low vision can use her reduced vision for learning about the world and for planning and doing tasks that need vision.

Total blindness
A person is unable to see light.

Functional vision
This refers to the use of vision for a particular purpose. Even small amounts of vision can be useful, for example to recognise a person close up, or to avoid objects. The use made of vision depends on a person's experiences and can vary with different conditions. Functional vision may be improved with refractive correction, low vision devices or instruction in the use of vision.

Visual acuity
It is a measure of the ability of the eye to see detail.

More information on visual acuity can be found in the Vision Screening chapter

Visual field
The whole area that is seen when looking straight ahead when the eyes, head and body are still. The peripheral visual field is the outer edges of the field.

Normal Field of View	Restricted Field of View