When you go in for an eye exam and they tell you that you have 20/20 eyesight, does that mean that you have perfect vision? Is it even possible to achieve better than 20/20 vision? And anyway, what exactly is “perfect vision”? The answers to these questions cannot be obtained until you are a bit more familiar with vision terminology. Read on to learn more.
Visual acuity refers to the sharpness of an individual’s vision. It is measured by an individual’s capability to make out numbers or letters on a uniform eye chart from a preset viewing distance.
Visual acuity is considered a static measurement, which means that you’re sitting completely still while the testing is being performed and the numbers or letters that you’re viewing are also stationary. Visual acuity is also tested under what is a considered high contrast setting. What this means is that the numbers or letters are black on the eye chart, while the chart’s background is white.
While visual acuity testing can be incredibly beneficial in determining the relative clarity of one’s eyesight in consistent conditions, this type of testing is not predictive of your vision’s quality in all types of situations. For instance, it is unable to predict how effective you would be able to see the following:
There are three main neurological and physical factors that assist in determining visual acuity:
Only light that’s focused on a highly sensitive and tiny section of the central retina, which is known as the macula, can influence the measurements of one’s visual acuity that is attained during an eye examination.
Visual acuity tends to be measured with Snellen fractions, which is talked about in more detail below.
It is difficult to determine the exact definition of the term eyesight. If you were to look it up in a dictionary, the definition would differ based on the dictionary or resource that you use. You may find “vision,” “ability to see,” “range of sight,” the sense of seeing,” or “view”. In many cases, the terms “visual acuity” and “eyesight” can be used interchangeably.
Vision is a much broader term when compared to the other two already examined in this article: visual acuity and eyesight. Besides the ability to see and sharpness of sight, vision often refers to a wide range of visual skills and abilities. These skills and abilities include the ability to follow moving objects with accurate and smooth eye movements, contrast sensitivity, color vision, focusing accuracy and speed, depth perception, and much more.
If the more comprehensive—and ultimately more exact—definition of the word vision is utilized, what most individuals refer to as 20/20 vision would really be referred to as 20/20 visual acuity. Reasonably, though, something like that will likely never happen. It seems that the 20/20 vision term is not going anywhere anytime soon.
The term 20/20 as well as other fractions like 20/40 and 20/60 are what are known as visual acuity measurements. They are also known as Snellen fractions, which are after the Dutch ophthalmologist Herman Snellen who developed this particular measurement system back in 1862.
In the Snellen visual acuity testing system, the highest number of the fraction is known as the viewing distance between the individual and the eye chart. In the U.S. this viewing distance is generally 20 feet, but in other countries, it is usually six meters.
At this particular testing distance, the fourth line up from the bottom of the chart has been standardized to be the normal visual acuity of 20/20. If an individual can identify the letter son this line but is unable to identify the letters on any of the lines below this one, then this means that the individual has 20/20 visual acuity.
Above the 20/20, the letters get larger and reflect measurements of poorer visual acuity, such as 20/25, 20/30, 20/40, all the way up to 20/200. Similarly, beneath the 20/20 line, the letters get smaller and correspond to better measurements of visual acuity, such as 20/15, 20/12, and 20/10.
At the top of the Snellen eye chart is a big E that most people are very familiar with and this letter matches 20/200 visual acuity. If you unable to recognize any letter except this one, this means that you’re legally blind.
As a general rule, the smallest letters on Snellen eye charts are the ones that correspond to the visual acuity of 20/10. If you have this level of visual acuity, then it means that you have twice as sharp eyesight as the eyesight of an individual with 20/20 (aka normal) vision.
It is possible to have better vision than 20/20. Individuals with healthy, young eyes often are able to identify the letters—at least some of them—on the 20/15 line, and sometimes even some of the ones on the lines smallest than that.
This may be partly due to enhanced printing methods that are available today versus those that were available in the 19th century, which was when Snellen was in the process of establishing the smallest of the letters that an individual should be able to distinguish with 20/20 vision. With that being said, a case can be made that 20/20 visual acuity (normal vision) nowadays is the capability to identify letters that are slightly smaller than the ones that are on the 20/20 visual acuity line of the standard Snellen chart.
Of course, on the other hand, there are individuals who live longer in the present day than they did when Snellen was around. Normal aging that occurs within the eye, like early cataracts, may justify considering relatively larger letters than those that are on the 20/20 visual acuity line as being representative of 20/20 vision among individuals who are 60 or older.
Regardless of this, however, if your eye doctor was to say that you had 20/20 visual acuity/vision and you wanted sharper eyesight, what could you do to obtain it?
If your 20/20 visual acuity does not appear to be sharp enough, it may be that your eyes have what is known as higher-order aberrations (or HOAs for short) that are unable to be corrected with soft contact lenses or regular eyeglasses. Your eye doctor can look for HOAs with state-of-the-art wavefront technology available in some eye clinics.
If the aberrations are a result of the irregular shape of the eye’s front surface, your visual acuity may be able to be improved with gas permeable contact lenses—also known as GP lenses. In many cases, GP lenses can be more effective than soft contact lenses or eyeglasses. This is due to the rigidity of the GP lenses and the fact that they ultimately replace the irregular front surface of the eye with a flawlessly smooth and curved surface so that the light can be focused more accurately.
An alternative is personalized wavefront LASIK. This is a custom laser vision correction surgical procedure that may be able to provide vision similar to wearing inflexible gas permeable contacts (which is often sharper tan the visual acuity that can be provided by soft contacts or eyeglasses) without having to deal with the daily care of contact lenses.
If you favor wearing glasses in order to correct the refractive errors, then you may be able to obtain sharper vision with special HD lenses as opposed to the standard lenses that are in eyeglasses.
It is virtually impossible to define “perfect” vision. Plus, the better question may be “Perfect for what?”
For instance, if you’re driving down the road on a particularly sunny day, exceptional visual acuity may be the primary factory in your vision satisfaction. However, your significant other, whose visual acuity is worse than your own, may be more content with his or her vision in the exact same circumstances due to the fact that she or he’s wearing sunglasses with polarized lenses and a special anti-reflective coating that has the ability to block glare and enhance contrast.
Consider an athlete with vision that is better than 20/20 who may struggle with his or her athletic performance due to the fact that he or she does not have specific dynamic visual skills that permit him or her with the ability to respond to on-the-move objects as rapidly as one of his teammates who doesn’t have as sharp of static visual acuity as he does.
If you are wanting to maximize the comfort and clarity of your eyesight in a variety of situations, you need to seek out the services of a competent optometrist or ophthalmologist for an all-inclusive eye examination and vision assessment.
If you would like to determine if laser vision correction may be able to improve your vision better than contacts or glasses, you may ask for a referral to a knowledgeable LASIK surgeon.
If you would like to take full advantage of your dynamic vision skills for physical activity or sports, talk to an eye doctor who specializes in sports vision and talk to them about specialized sports vision training. This is a specialty here at Performance Vision.
If you have a child that has been notified of 20/20 vision yet is still struggling with vision problems, such as eye strain, in school, an experienced eye doctor can evaluate your child for potential learning-related vision issues.