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What is visual acuity?

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Visual acuity is the clarity and sharpness of your sight. It varies greatly from person to person and in many cases can be managed with prescription glasses.

Managing visual acuity

A lack of visual acuity could be due to an eye condition such as short or long-sightedness, presbyopia or astigmatism. These conditions are easily treatable with prescription glasses. Managing visual acuity is especially important for drivers. To drive safely, your vision must pass the minimum vision standard set by the DVLA. Certain occupations demand higher standards.

Signs of low vision

Signs you may have a problem include loss of central vision - blind spots appear at the centre of the field of vision; loss of peripheral vision (‘tunnel vision’) – an inability to see to the side; blurred vision – objects appear out of focus or hazy at certain distances; poor night sight and sensitivity to glare.

Related eye conditions

Low vision can stem from a number of conditions or injuries, such as diabetes or a brain injury. It can also be related to other eye conditions, which are listed below.

Glaucoma

Glaucoma is a group of eye conditions in which a build-up of eye fluid damages the optic nerve.

Diagram showing the difference between an eye with normal vision and an eye with glaucoma

Cataracts

Cataracts are where cloudy patches form in the lens of the eye.

Age-Related Macular Degeneration (AMD)

AMD is the gradual loss of central vision due to the deterioration of the macula – the part of the retina responsible for central vision – over time.

An eye examination is a vital health check. It can discover and prevent conditions that could harm your vision - and only takes around half an hour.

What is 20/20 vision?

Dutch ophthalmologist Dr. Hermann Snellen devised his eye chart of different sized letters in 1862, specifically to measure visual acuity. The term 20/20 vision, is a reference to being 20 feet away from the eye chart. When metric took over, this term was replaced with 6/6 vision, as the test is conducted from 6 metres away. Having 20/20, or 6/6 vision, means you can see the same line of letters at 20 feet that a person with normal vision can also see at 20 feet, but this doesn't mean you have perfect vision. The test doesn't take into consideration the peripheral vision, colour definition or the depth of your perception. All of these are part of a full eye examination and can help your optician identify any eye conditions and the best way to correct your eyesight if needed.

Low vision aid technology

Wearable assistive technology devices for low vision

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