Visual acuity measures vision clarity, indicating how sharply details can be perceived. This precision in processing visual information impacts how individuals interact with their surroundings and interpret the world.
Understanding Visual Acuity
Visual acuity quantifies the sharpness or clarity of vision. The Snellen eye chart, with its rows of letters decreasing in size, is a common tool for this measurement. During an eye examination, individuals usually stand 20 feet from the chart and read the smallest line of letters they can discern.
The results are commonly expressed as a fraction, such as 20/20 or 20/70. The top number, 20, represents the standard testing distance in feet. The bottom number indicates the distance at which a person with unimpaired vision (20/20) could clearly see what the test subject sees at 20 feet. A measurement of 20/70 vision means an individual must be as close as 20 feet to see what someone with 20/20 vision can see clearly from 70 feet away.
Experiencing 20/70 Vision
A person with 20/70 vision experiences noticeable blurriness, particularly when viewing objects at a distance. What a person with 20/20 vision sees clearly from 70 feet away would appear indistinct to someone with 20/70 vision at a mere 20 feet. For instance, a street sign easily readable by most drivers from across an intersection might only be a fuzzy shape for someone with 20/70 vision until they are much closer.
Recognizing faces from a short distance becomes challenging, as facial features tend to blend together, making individual identification difficult unless the person is very near. Similarly, text on a television screen, a billboard, or a distant building would lack sharp edges and appear blurred. Detail is significantly diminished, making fine distinctions problematic. This visual experience can be likened to looking through a slightly smudged or out-of-focus lens, where clarity is compromised across various distances.
Navigating Daily Life with 20/70
Living with 20/70 vision presents practical challenges. Tasks requiring clear distance vision, such as reading road signs or recognizing people from afar, become difficult. For instance, navigating unfamiliar areas while driving can be more demanding because street names and directional signs may not be legible until a driver is very close, potentially impacting reaction time.
Reading ordinary print, like that in books or newspapers, often requires holding the material much closer or using larger print to discern the text. Watching television may necessitate sitting significantly nearer to the screen to make out details and facial expressions. While 20/70 vision is considered “low vision” and a moderate visual impairment, it is not typically classified as legal blindness, which is generally defined as 20/200 or worse in the better-seeing eye with best correction. Driving eligibility can be impacted, with some jurisdictions allowing driving with restrictions such as daylight-only driving or specific speed limits.