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20/20 Vision Calculator for 2020

Created by Dominika Śmiałek, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Based on research by
Bénédicte M. J. Merle, Gwendoline Moreau, Anna Ozguler, Bernard Srour, Audrey Cougnard-Grégoire, Marcel Goldberg, Marie Zins & Cécile Delcourt Unhealthy behaviours and risk of visual impairment: The CONSTANCES population-based cohort; Scientific Reports - Nature; April 2018
Last updated: Feb 28, 2024


Imagine a day without scrolling through your phone, watching Netflix, or having to read road signs while driving somewhere. Sounds tough, right?

Around 2.2 billion people worldwide have some form of vision impairment. What's even more frightening is that almost 50% of cases could have been prevented. In the USA, the number of visually impaired people is said to double by 2050. This enormous increase is due in part to us spending more and more time in front of screens, both at work and at home.

As WHO stated in their resolution on February 6, 2020, early detection and prevention are essential if we want to reduce blindness and visual impairment. Their recommendations highlighted that lifestyle choices are a preventable factor. The American people's lack of knowledge about eye health may be putting their vision at risk, according to a survey released by the American Academy of Ophthalmology. With our calculator, you can see how your lifestyle affects your eyesight. We won't leave you with meaningless figures either - you'll find some advice on what you can do to make your eyes healthier. For more details on how the calculator works, take a look at the article below.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. All information on this website is for informational purposes only and is not intended to serve as a substitute for medical consultation. Always consult your results with a health care provider.

20/20 vision? What does that even mean?

20/20 vision means that you can see perfectly from a distance, without the need for glasses. This original notation comes from the Snellen board, used to test your visual acuity.

Snellen chart

Remember at the ophthalmologist, you'd be told to read from those boards where the letters on them gradually get smaller and smaller? A 20/20 score means that you can read the optotype 20 from 20 feet away (around 6 meters). In our calculator, we refer to vision impairment as 20/40 vision acuity. This means that for a person who can read something perfectly from 40 feet away, this level of visual impairments means you would have to be 20 feet away.

What about the diopter conversion? You'll find the solution in the table below:

Diopters

Snellen score

0.00

20/20

-1.00

20/40

-2.00

20/80

-3.00

20/150

-4.00

20/300

-5.00

20/400

Can I see any better than 20/20?

Some people see much better than what we consider normal vision. In that case, their result maybe 20/10. That means they can see from 20 feet what the average healthy person sees from only 10 feet away.

People this eagle eyed tend to end up as pilots or athletes (Olympic medalists!), and comprise about 1% of the total population. Interestingly, the difficulty in estimating this number of people comes from the fact they rarely visit the ophthalmologist - after all, they don't need to. The structure of our eye limits the maximum visual acuity to 20/5. In a large number of children, a result of 20/15 is typical.

Why does my vision get worse every year?

Generally speaking, physiological sight deterioration is related to age. However, young people often develop myopia, particularly if they have genetic predispositions (e.g., their parents have a major visual impairment) or if they grow too fast. In the second scenario, the eyeball does not keep up with the growth of the rest of the body and becomes too short. This tends to be temporary though; the eyeball catches up once the kid stops growing.

For adults, however, there are two independent phenomena that can occur:

  1. After the age of 40, lenses lose their capacity for accommodating various shapes and become less flexible. The effect? Your close-up vision gets worse. It doesn't matter if you have had myopia or hyperopia before, the effect is still the same.
  2. After 70, due to changes in light refraction within the eyeball, vision deteriorates by +1.5 dioptres, and by +2.5 dioptres by the time you reach 80. Fortunately, if you are shortsighted, your defect 'retreats' by the same magnitude.

Other conditions that are more likely to affect the elderly, such as diabetes and hypertension, do not contribute to good visual acuity either.

A scheme of an eye with presbyopia

Use of the calculator - a short guide

This Omni calculator is based on the findings of CONSTANCES cohort, a prospective cohort study of almost forty thousand members from the general adult population in France.

Let's go through step by step what is required for a result:

  1. Activity - 1 to 3 points are given for each answer.

Look at the first field - the question concerns the level of activity that goes with your job. If you are retired, select the option that most closely corresponds to your last job.
* Cycling, hiking, walking - this question refers to regular, longer hikes, cycling trips or walks.
* Household activities - such as house cleaning, gardening. Again, how much time you spend during the week doing this.
* Gym, team sports - this is all about being active in your free time - team games, running, cardio exercises all count. Choose how many hours a week you spend dloing such things.
In the study patients were divided into 3 physical activity levels:

  • Sedentary (score 1–2)
  • Moderately active (score 3)
  • Highly active (score 4–6).

Sedentary level was considered an unhealthy behaviour.

  1. Diet - studies show that a Mediterranean diet (MedDiet) is linked to healthy eyes, so the calculator evaluates your diet against one; between 1 and 5 points are given in each category
    • On top there are fruit, vegetables, and legumes, which have a positive effect on your eyes. Below them are some more eye-protecting products, fish and cereals.
    • White and red meat, as well as dairy products, have an unfavorable effect on your body, and according to the MedDiet ideology, their consumption should be limited.
    • Olive oil - daily use is highly recommended.
    • Alcohol - Heavy drinking (more than 210 g per week in men and more than 140 g of alcohol in women) were considered a separate unhealthy behavior.

MedDiet score is interpreted as:

  • High (≥31)
  • Intermediate (27–30)
  • Low (24–26)
  • Very low (0–23).

In the study the calculator is based on, very low/low/intermediate scores were considered an unhealthy behavior.

  1. Smoking - first, choose if you have ever smoked.
    • If you smoke, think about quitting (smoking damages not only your vision but also your lungs, and heart, and increases the risk of cancer!). Please check out our lung cancer risk calculator. Whether you still smoke or already quit smoking, choose how many cigarettes you smoke (or smoked) a day for how many years.

Smoking status was assessed based on the number of pack-years. It is the number of packs (20 cigarettes) smoked per day multiplied by years of smoking. Heavy smoking (≥20 pack-years) was considered an unhealthy behaviour.

And so in practice, what can I do to keep my sight going?

It might sound trivial, but start moving. You probably won't change your job (81% of office workers spend between four and nine hours a day sitting at their desks). As the job makes up about 30% of your time, the next 30% is sleep - it is worth making sure that you spend your free time actively. WHO recommends limiting the amount of time spent being sedentary.

As for the time you spend in front of screens, we know how hard it is to limit it with today's lifestyle. That's why it's useful to bear in mind a simple trick: 20-20-20. That is, every 20 minutes look at an object that is 20 feet away from you for 20 seconds.

How a person with myopia sees without glasses.
How a person with myopia sees (By gerlos, CC BY-ND 2.0

Quitting smoking is also a good thing. Tobacco harms nearly every single one of your organs. Find out more on this CDC website.

When it comes to diet, try to eat more cereals, legumes, and, of course fruit and vegetables. Cut down on meat, reducing the consumption of red meat in particular will help our planet. Please check our our meat footprint calculator. And on top of all of that, olive oil. Not only does it contain antioxidants, but also good fats, called monounsaturated fatty acids. In Mediterranean countries, raw olive oil makes up the basis of all of their meals (including breakfast!).

Dominika Śmiałek, MD, PhD candidate
Sex
Male
Activity 🏃
Regular and diversified exercises are associated with a lower risk of vision impairment.
💼 How active are you at work?
Moderately active
🏡 Household activities
Less than two hours/week
🚲 Cycling, hiking, walking
Less than two hours/week
⚽ Gym, team sports
Less than two hours/week
Diet 🍲
A Mediterranean diet is associated with a lower risk of vision impairment.
🍅 Vegetables, fruits and legumes
8-12
servings/wk
🐄 Red and white meat
2-4
servings/wk
🌾 Cereals
>4.5
servings/wk
🐟 Fish
2-3
servings/wk
🍼 Dairy
2-3
servings/wk
🔸 Olive oil
0.75-7
servings/wk
🍷 Alcohol
3-4
glasses/wk
Smoking 🚬
Smoking directly accelerates major causes of severe visual impairment.
Do you smoke?
No, I have never smoked
Results
SCORE: 0
Interpretation: risk of vision impairment not increased [1].
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