It is the end of February and the first 2 months of 2020 have already passed so it might be the right time to discuss the analogy between the year 2020 and vision. What is the fuss about 20/20 then?
Many visual acuity scales exist
In certain countries, such as the US and to an extent the UK, where the main system of units remains imperial rather than metric, 20/20 describes the most commonly used one’s normal visual acuity. In some other countries or in some instances visual acuity scale can also be given in decimal, percentage, the minimum angle of resolution, etc. It is important to remember that 20/20 visual acuity equals 6/6 or 100% or 1.0 or 1 minute of minimum angle of resolution. 20/20 scale that is most commonly used in the US is the 20-foot visual acuity scale that is carried out at a distance of 20 feet (6 meters). Visual acuity of 20/20 (or 6/6) means that a person can see a detail from 20 ft (6 meters) away – the same as a person with normal eyesight would see from 20 ft (6 meters). If a person from 20 ft (6 meters) can only spot such detail that a healthy person would see from 40 ft (12 meters), their visual acuity would then only be 20/40 (or 6/12 in meters), which equals to 0.5 and 50% in decimal and percentage scale, respectively.
Visual acuity is limited by histological features of the retina
Visual acuity describes the maximum clarity of vision one can achieve. The values are usually corrected for the most common refractive errors hence best-corrected visual acuity (BCVA). A person whose visual acuity is 20/20 either without or with correction (glasses or contact lenses) has got, by definition, normal visual acuity. Human visual acuity is the function of photoreceptors in the macula as is limited by the density of cones in the fovea. In young healthy individuals, the visual acuity is about 1 minute of the minimum angle of resolution, which reflects about one-tenth of a millimeter (4 thousandths of an inch) at reading distance. Due to certain anatomical and histological variants among individuals, though, some can even see slightly beyond that.
“VISION 2020: The right for sight” also refers to the global initiative launched 20 odd years ago by the World Health Organization (WHO) and the International Agency for the Prevention of Blindness (IAPB). At the time of its launch in 1999, they have a vision that by the year 2020 nobody in the world is needlessly visually impaired and that those with unavoidable vision loss can achieve their full potential. Unfortunately, as of 2020, we are not just there yet…
So, there you have it, the meaning of 20/20 vision in the year 2020. Stay tuned for more interesting content to come!