Scroll Down

If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. 20/20 vision is the term used to express normal visual acuity. Laser eye surgery (LASIK) is the best way to correct your eyesight to achieve 20/20 vision or better again. 

Visual Acuity - What is 20/20 vision?

If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. 20/20 vision is the term used to express normal visual acuity or the sharpness of your vision. The visual acuity measurement is assessed using an eye chart measuring system developed by a Dutch ophthalmologist, Herman Snellen, in 1862. In the Snellen visual acuity system, the top number of the fraction is the viewing distance between the patient and the eye chart. In North America and America this distance is 20 feet. In New Zealand we use the metric system and refer to it as 6 meters.

The Snellen chart has a 20/20 line and those letters that are smaller below the line correspond to a visual acuity that is better than 20/20 vision, such as 20/15 or 20/10. Most young people with healthy eyes can read below this line.

The increasingly larger letters above the 20/20 line on the Snellen chart correspond to poorer visual acuity measurements eg. if you have 20/40 (or 6/12) vision then you will just be able to see something from a distance of 20 feet (6 meters) that a person with perfect eye sight can see from 40 feet (12 meters).

The single large “E” at the top of the Snellen chart corresponds to 20/200 visual acuity and if this is the smallest letter that you can see with your corrective lenses in front of your eyes, you are classified as legally blind.

What determines Visual Acuity?

Visual acuity is determined by three physical and neurological factors:

how accurately the cornea and lens of the eye focus light onto the retina,

the sensitivity of the nerves in the retina and vision centres in the brain, and

the ability of the brain to interpret information received from the eyes.

When most people say “20/20 vision” they mean “20/20 visual acuity”.

What is perfect vision?

Having “20/20 vision” does not necessarily mean that you have perfect vision. Some people can see better than 20/20 and they normally have a higher sensitivity in their retina. The terminology refers to the sharpness or clarity of vision at a distance. Visual acuity is tested under clinical conditions. During the test you are sitting still and the letters are also stationary, making it a static test. In normal conditions our eyes are focusing and responding to both moving and non moving objects at a distance, middle range and up close. Visual acuity is also tested under high contrast conditions; the letters on the eye chart are black and the background of the chart is white. In normal life objects are both coloured and similar in brightness to their background.

Vision is a more general term including a wider range of visual skills such as contrast sensitivity, the ability to track moving objects with smooth and accurate eye movements, colour vision, depth perception, the ability to focus with speed and accuracy, contrast sensitivity, peripheral awareness or side vision and eye coordination.

The terms “vision” “eyesight” and “visual acuity’ are often used interchangeably.

Will laser eye surgery give me 20/20 vision?

Some people can see well at a distance but are unable to bring nearer objects into focus. This is hyperopia (far sightedness). Other people can see up close but have difficulty with distance vision, such as reading roadsigns when driving, this is myopia (near sightedness). Most of us experience a gradual decline in the quality of our eye sight once we reach over 40 years. This is because our lenses tend to become less flexible and it becomes difficult to read up close or in the evening without sufficient lighting. This is call presbyopia.

Laser eye surgery (LASIK) is the best way to correct your eyesight to achieve 20/20 vision or better again. The procedure uses a type of laser to gently reshape the surface of the eye and can correct common vision related issues such as far sightedness, near sightedness, astigmatism and presbyopia. Myopia can be treated upto -10.0D and Hyperopia upto +4.0D.

Laser eye surgery is a simple, quick and painless procedure that provides you with a lifetime of no longer requiring vision correction glasses or contact lenses. Over 98% of people who have laser eye surgery achieve the result of 20/20 vision or better.

 

Phone Bowen Eye Clinic on 0800 69 2020 to book a free suitability assessment for laser eye surgery with Dr Reece Hall in Wellington, Palmerston North, Waikanae or in our Nelson clinic and start your journey towards 20/20 perfect vision today.