Someone with "20/30 vision" stands 20 feet from a reading chart but sees letters and objects that people with normal vision see 30 feet away from the chart, according to the University of Iowa. The first number, 20, is the distance from the eye chart and the second number, 30, shows the size of the letters read at that distance.
A patient with 20/30 vision may need corrective lenses to see properly. The University of Iowa also explains that about 35 percent of Americans have 20/20 vision, meaning they see things normally. Having 20/20 vision describes someone who has sharp, clear vision at a distance. The American Optometric Association explains that other factors including depth perception, peripheral vision and color discernment determine a person's overall seeing ability.
The ability to see from a certain distance is measured by an eye chart hanging on a wall. The chart has 11 rows of letters, with a large "E" at the top. A patient able to read the "E" and nothing else on the chart has 20/200 vision, according to All About Vision. Having 20/200 vision is the definition of legal blindness in the United States. Drivers of vehicles need to have at least 20/40 visual acuity with corrective lenses. The line of 20/20 vision is the fourth row from the bottom of the chart. If a person can read the very bottom line of the chart, that person has 20/5 vision.Learn More
Blurred vision in one eye can be caused by a variety of factors that include eye strain, infections, eye allergies and sleepiness, according to All About Vision. Blurry vision or darkness in one eye can also indicate severe medical or vision issues, such as stroke or retinal detachment.Full Answer >
According to Healthline, blurred vision can signify a variety of conditions such as cataracts, nearsightedness, injuries to the cornea, glaucoma and eye infections. Blurry vision can also occur in individuals with diabetes or as a result of the natural aging process. It is important for anyone experiencing unexplained symptoms of blurred vision to consult with a vision specialist to ensure an accurate diagnosis.Full Answer >
According to WebMD, blurry vision may stem from a number of sources, including an eye injury, nearsightedness or allergies. Hay fever and indoor allergens may also cause blurriness in the vision. Dry eye, pink eye and foreign objects in the eye also cause blurriness.Full Answer >
In humans, perfect vision is a visual acuity of 20/20. The first number in 20/20 refers to the distance at which a person can see a particular object in daylight; the second number refers to the distance a human eye with perfect vision can see the object.Full Answer >