Around 2 million people in the UK have low vision, problems with eye sight that cannot usually be corrected with glasses, contact lenses or eye surgery.
A person with low vision still has some sight.
Low vision includes different degrees of sight loss from having blind spots, poor night vision, and problems with glare to almost a complete loss of sight.
Low vision tests
Visual acuity is measured by reading letters from an eye chart called a Snellen test while wearing any prescribed glasses or contact lenses.
Around one person in 30 is living with sight loss. The charity RNIB says that to be registered as severely sight impaired, or blind, generally sight falls into one of the categories below:
- Visual acuity of less than 3/60 with a full visual field
- Visual acuity between 3/60 and 6/60 with a severe reduction of field of vision, such as tunnel vision
- Visual acuity of 6/60 or above but with a very reduced field of vision, especially if a lot of sight is missing in the lower part of the field.
To be registered as sight impaired or partially sighted, a person would generally have:
- Visual acuity of 3/60 to 6/60 with a full field of vision
- Visual acuity of up to 6/24 with moderate reduction of field of vision or with cloudy or blurry central vision
- Visual acuity of up to 6/18 with a large part of the field of vision missing or much of the peripheral vision being missing.
The most common types of low vision include:
- Loss of central vision. A condition in which a blind spot is in the centre of one's vision
- Loss of peripheral (side) vision. Inability to see anything to either side, above or below eye level. Central vision, however remains intact
- Night blindness. The inability to see in poorly lit areas such as a theatre, as well as outside at night
- Blurred vision. A condition in which objects both near and far appear out of focus
- Hazy vision. A condition in which the entire field of vision appears to be covered with a film or glare
What causes low vision?
There can be one or more causes of low vision. Low vision is usually the result of disorders or injuries affecting the eye or conditions that affect the entire body such as diabetes. Some of the most common causes of low vision include age-related macular degeneration, diabetes and cataracts. Low vision may also result from cancer of the eye, albinism or a brain injury. Anyone who has had or is at risk of these disorders has an increased risk of low vision.
How is low vision diagnosed?
An eye examination by an optician or ophthalmologist (eye doctor) can diagnose low vision. You should make an appointment with an optician if your vision difficulties are preventing you from daily activities such as travelling, cooking or working. He or she will perform a variety of tests involving the use of lights, magnifiers and special charts to help test visual acuity, depth perception and visual fields.