central and peripheral vision illustrated with different coloured regions

Central Vision vs Peripheral Vision

Eye sight can be seen (pun very much intended) as being comprised of two main functions: central and peripheral.

Most associate central vision with focusing on particular objects of interest, while peripheral vision is when something to the side attracts attention. Both act as a function of the human retina, which is made up of two types of photoreceptors: rods and cones. Rods are responsible for vision at low light levels, while cones are active at higher light levels.

However, both central and peripheral do much more and provide use that many may not be aware of.

 

Central Vision

Central vision is probably the one that is more straightforward. Perhaps regarded as the more important of the two, central vision is responsible for most of the active functions that someone uses.

Reading, driving, recognising colours and shapes, and general focus-based detail-oriented sight tasks are fulfilled by the use of central vision.

reading a book with a finger

Central vision allows pinpoint reading

This all comes from the very centre of the retina at the back of the eye, also known as the macular and is where there is a high concentration of cones. If this area is damaged, it can cause vision to become blurry and dull. Eventually it may lead to dark patches appearing.

 

Peripheral Vision

The general public are often aware of the importance of peripheral vision. It is not something that people actively use, but this doesn’t mean that it is less important than central vision.

Peripheral vision helps to process spatial information received through the eyes and is an important cog in our innate fight or flight response system.

Any activity that involves space (and many ones that don’t) can be improved with better peripheral vision. This is due to spatial information combining with body mechanics to produce correct and precise movements.

For example, if someone is dribbling a football towards a goal, their peripheral vision can inform them of an impending opponent coming from the side. Good peripheral vision gives the player the opportunity to avoid the challenge posed. Bad peripheral vision may leave the player dining on dirt.

man juggling a football on the ground

Which may give you an opportunity to show off your juggling skills

Light sensitivity is also associated with peripheral vision. People will often see better in low light situations with their peripheral vision rather than looking straight with their central vision. This is largely due to the increase in rod density in the periphery which are more sensitive to light.

In addition, peripheral vision plays an important part in scene gist recognition, allowing the individual to access related long-term memory with just a single eye fixation. This then helps to guide the individual in their subsequent actions.

With central vision loss being one of the most common causes of blindness, more and more people are left to rely on actively using their peripheral vision, something that may not be as intuitive. Fortunately, it is possible to train and improve peripheral vision usage to help replace some of the functions that central vision performed.

focusing on the snellen chart with glasses 20/20 vision

What is 20/20 vision?

20/20 vision is normally used to describe perfect sight.

However, this is not entirely accurate.

20/20 vision (or 6/6 if you are in the UK) actually refers to what is seen as “normal visual acuity” at a distance of twenty feet (or six metres). The first number represents what an individual can see clearly at a certain distance. The second number indicates the distance at which normal vision would be able to distinguish.

Confused?

Essentially, 20/20 vision means that at twenty feet an individual is able to clearly see what someone with normal vision is able to at twenty feet.

Thus, ‘normal’ visual acuity.

This form of measurement comes from Herman Snellen, a Dutch ophthalmologist who developed this system in 1862.

snellen chart

Bog-standard Snellen Chart

After years of research, Snellen determined that 20/20 was the benchmark for standard visual acuity.

The error in believing that this is perfect vision comes from the fact that this form of measurement does not take into account many other factors. Peripheral vision, colour, depth perception, and focusing ability are just some of the other elements of someone’s vision that are omitted.

So, does 20/20 vision mean that you have reached the pinnacle of visual acuity?

Sadly, no.

Someone with 20/10 vision would be able to clearly see something twenty feet away that normally would need a distance of ten feet. While this may seem like a form of “super human vision”, it is not as uncommon as you may think.

This is due to variety of reasons:

  • With technology progressing as it has, the advent of effective eye surgery has been able to improve acuity to above “standard” levels.
  • Believe it or not, brain training has been proven to improve visual acuity.
  • Genetics.
  • The age of the Snellen chart. Having been around for almost 200 years, printing methods for the chart have made a vast leap in terms of clarity which may have led to a greater majority of the population being able to read smaller lines.

For the best visual acuity, there have been reports of aboriginal people with roughly 20/5 vision. For context, this is approximately the visual acuity that eagles have.

While reaching this level may be a pipe dream for many, OXSIGHT glasses have an easy zoom function which can, in theory, give users around 20/7 vision, allowing them to see in a way that surpasses even those with above average visual acuity.