In terms of measuring the power of visual acuity, 20/30 vision is a term used simply for the capacity of having clear sight of an object at a distance of 20 feet which otherwise is recognizable by an ‘average eye’ at a distance of 30 feet. Thus, in terms of measuring the power of visual acuity of a person, 20/30 vision indicates a mild degree of vision loss, also known as near-sightedness.
Delving into the technical understanding of the term 20/30 vision, the first number represents ‘optical infinity’ which is where light rays form the image of an object that your eyes intercept i.e. 20 feet. The second number represents the distance at which the object can be seen by a person with average visual acuity. The increasing value of second number therefore, indicates rising degree of visual impairment and vice versa.
How is 20/30 Vision Measured?
If you have ever been to an eye specialist, you surely would have had the experience of taking a test on the alphabet chart pasted on one of the walls, known also as the Snellen chart. Although there are over 100 tests to measure and assess different qualities of vision, the Snellen chart is referred as the most basic eye test and requires you to read 11 rows of varying sizes of alphabet while standing at a distance of 30 feet from the chart.
If a person is unable to read and focus on the letters from this distance, which are typically visible from 20 feet apart, then they are said to have weak vision and are suggested to use corrective lenses.
What is the ‘Standard’ Vision?
According to American Optometric Association, the standard of normal vision acuity for an average person is when they can see an object clearly while being 20 feet away from it. This is usually considered as a baseline standard and termed as 20/20 vision, with which the vision of other people is compared and the degree of visual impairment is determined.
The eye’s function is to form an image of whatever you set eyes on in the environment, however it is important to understand that there are several small specialized domains of functions involved which together form ideally perfect vision. These are domains such as central vision, peripheral vision, color perception, depth perception, visual clarity etc. The 20/20 vision of a person means that they have perfect visual acuity, but other aspects of vision are not inclusive in this term.
In comparison to this standard, the concept is that people who are said to have vision with/ or of higher numbers than 20/30 are not able to see objects that are farther away from with visual clarity and sharpness, than they used to prior to the detrimental vision. Increasing numbers indicate intensifying form of near-sightedness.
Understanding what causes 20/30 vision?
The 20/30 vision basically refers to a deteriorated quality of visual acuity of a person, which can also be defined as the power of the eye to distinguish fine detail in the image that it forms. Such a person cannot see the objects farther from him with clarity, they are either blurred or not recognizable. This weakened visual acuity depends upon some optical and neural factors which are as follows:
- sharpness of retinal focus
- health and functioning of retina
- functioning of visual interpretative region of brain
Problems occurring in either of these factors can lead to a lack of visual clarity and vividness. Most commonly, 20/30 vision results from a refracted error which is how light refracts within the eyeball to form an image. This error may lead to 20/30 vision.
Less probable causes involve damage to pathways in the brain, such as under-development of the visual brain during early years or having suffered from traumatic brain injury or stroke which may incapacitate a person from having clear vision.
How the World appears if you have 20/30 Vision?
For a person with 20/30 vision, every object in the environment appears with reduced clarity and a slight blur. If you are in a classroom sitting in the back row then you may have to change your position to be able to read the blackboard properly, although you probably could make an estimated guess based on the slightly blurry judgement.
From distinguishing the boundaries of something written on a far away billboard or peeking through the window to see flowers along your fence, things can be befuddling. As the boundaries do not stand out if you have 20/30 vision, you might be seeing the world in less than the best quality HD view, though there certainly are several ways open to retain your high quality vision or compensate for it. Read on for more.
Corrective Solutions for 20/30 Vision
Since 20/30 vision is a relatively mild degree of visual impairment, people who have this can easily compensate for the defect in their vision by wearing corrective lenses or glasses. As this defect can occur in either the left or right eye (or both), an eye care professional can analyze and determine it while also prescribing the specific corrective lens that provides the most clarity, comfort and accurate vision.
Prescriptions typically mention the power specifications for each eye, which is measured in quarter-diopter steps (0.25 D). Here’s a convenient guide to decipher the meaning of your eyeglass prescription.
According to the prescription, you can get your spectacles tailored as per the assigned diopter figure from any nearby optics store and wear these to see with ease.