What is 20/20 vision?

You might have heard the phrase “20/20 vision” or even used it yourself, without knowing its literal definition. So, what is 20/20 vision, exactly? Here we’ll explain what the term refers to, how you achieve it, and what it means for you.

Does it mean perfect eyesight?

20/20 vision is a way of describing visual acuity, or the sharpness of your vision. The first number – the top of the fraction – refers to the distance from the patient to the eye chart, usually 20 feet. If you can read the line of letters on the chart that denotes ‘normal’ eyesight from this distance, you are said to have 20/20 vision. (If you can only make out the larger lines you may have 20/40 or 20/60 vision. 20/40 vision is the minimum required for driving).

The bottom number of the fraction refers to what a patient can see in comparison to someone who is considered to have normal vision. Therefore, 20/20 means that at 20 feet, one sees what a normal person can see at 20 feet. 20/40 means that at 20 feet, one sees what a normal person can see at 40 feet i.e. twice as bad. 20/10 is ‘super vision’, which means a patient can see at 20 feet what a normal person can only see at 10 feet i.e. twice as good as ‘perfect’ vision.

But what is 20/20 vision in terms of perfect eyesight? The truth is, 20/20 vision isn’t the best result possible. Many people can make out even smaller characters from this distance, with visual acuity measurements as high as 20/15 or 20/10. “The reality is that 20/20 vision is actually quite average,” says Allon Barsam. “The fact that 85% of our patients see twice as well as 20/20 and at the limits of human vision is much more impressive.”

How do you achieve it?

If you have refractive errors or other problems with your eyesight, the idea of having 20/20 vision (or even better) may seem incredible. For most patients seen by Allon Barsam, however, it’s an eminently achievable goal.

For patients with myopia or hypermetropia, 20/20 vision can usually be achieved through laser eye surgery. Long-sighted and short-sighted patients can have the shape of the cornea surgically altered with bladeless technology to correct their focus, resulting in normal vision once again. Other refractive errors, such as astigmatism, can also be treated in this way.

Patients with cataracts can undergo cataract surgery to remove the cloudy lens that causes blurred vision.
Other treatment options, including refractive lens exchange and implantable collamer lenses (ICL) can also result in 20/20 vision for many patients.

Provided that you don’t have any underlying eye problems, the numbers look good, with 100% of patients with common prescriptions achieving 20/20 vision or better.

Life-changing surgery

For many patients, achieving 20/20 vision after years of contact use or glasses wearing is, literally, eye opening. One patient who regained near-perfect eyesight after years of poor vision was “absolutely thrilled” at the difference that lens implant surgery made to her life. Another describes the revolutionary impact that Z-LASIK laser eye surgery has had on her vision and consequently, her confidence and wellbeing. 

The human lens is able to focus at distance and then at near when you are younger because it is flexible and can change its shape. This happens automatically due to the action of thousands of little fibres called zonules that contract and relax to pull on the lens. As you age the substance of the lens becomes stiff and rigid and the lens gradually loses its ability to change shape and hence focus for near. This change, called presbyopia, is the beginning of a series of changes to the substance of the lens that leads to cataract formation later in life.

Many patients hate wearing reading glasses or bifocals, or hate that they keep having to switch between glasses for different tasks. They often don’t like the fact that reading glasses make them look older than they feel! We are more active, youthful, and affluent than generations before, and have a strong desire to remain as active as possible. Unfortunately, we live in an increasingly near sighted world, where smart phones, computers and Kindles make near visual tasks increasingly common.

Treatment options

Technological advances in eye surgery now offer a number of effective options for people who want to be less dependent on reading glasses. There are 2 effective options for people seeking to be less dependent on reading glasses:

• Laser vision correction with mono-vision
• Refractive lens exchange surgery with multifocal intraocular lenses