New! Sign up for our free email newsletter.
Reference Terms
from Wikipedia, the free encyclopedia

Visual acuity

Visual acuity (VA) is acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye, the sensitivity of the nervous elements, and the interpretative faculty of the brain.

VA is a quantitative measure of the ability to identify black symbols on a white background at a standardized distance as the size of the symbols is varied. The VA represents the smallest size that can be reliably identified. VA is the most common clinical measurement of visual function. A visual acuity of 20/20 is frequently described as meaning that a person can see detail from 20 feet away the same as a person with normal eyesight would see from 20 feet. If a person has a visual acuity of 20/40, he is said to see detail from 20 feet away the same as a person with normal eyesight would see it from 40 feet away. It is possible to have vision superior to 20/20: the maximum acuity of the human eye without visual aids (such as binoculars) is generally thought to be around 20/10 (6/3). Recent developments in optometry have resulted in corrective lenses conferring upon the wearer a vision of up to 20/10. Some birds, such as hawks, are believed to have an acuity of around 20/2, which is much better than human eyesight. Many humans have one eye that has superior visual acuity over the other. If a person cannot achieve a visual acuity of 20/200 (6/60) or above in the better eye, even with the best possible glasses, then that person is considered legally blind in the United States. A person with a visual field narrower than 20 degrees in diameter also meets the definition of legally blind.

Related Stories
 


Health & Medicine News

October 29, 2025

Finnish scientists found that eicosapentaenoic acid (EPA) from fish oil impacts each person’s metabolism uniquely. Participants showed strong but short-lived increases in EPA levels, with significant differences in lipid profiles. The results ...
New research reveals that intelligence plays a key role in how well people process speech in noisy environments. The study compared neurotypical and neurodivergent individuals and found that cognitive ability predicted performance across all groups. ...
A team of scientists discovered a hidden antibiotic 100 times stronger than existing drugs against deadly superbugs like MRSA. The molecule had been overlooked for decades in a familiar bacterium. It shows no signs of resistance so far, offering ...
An international team of researchers led by scientists from the Max Planck Institute for Evolutionary Anthropology in Leipzig, working with 15 collaborators around the world, has conducted the most comprehensive study yet of lifespan differences ...
ETH Zurich scientists have created “MetaGraph,” a revolutionary DNA search engine that functions like Google for genetic data. By compressing global genomic datasets by a factor of 300, it allows researchers to search trillions of DNA and RNA ...
A new study offers reassurance about the safety of certain processed fats found in everyday foods. Interesterified fats made from palm or plant oils didn’t raise cholesterol or cause metabolic harm in healthy adults. The research challenges the ...
Researchers found that COVID-19 mRNA vaccines significantly increased survival in lung and skin cancer patients undergoing immunotherapy. The vaccine appears to prime the immune system in a powerful, nonspecific way, enhancing cancer treatment ...
New research reveals that walking in longer, uninterrupted bouts of 10–15 minutes significantly lowers cardiovascular disease risk—by up to two-thirds compared to shorter strolls. Scientists from the University of Sydney and Universidad Europea ...
Researchers at UC Davis discovered that adding a banana to your smoothie may drastically reduce the absorption of flavanols — powerful compounds linked to heart and brain health. The culprit is polyphenol oxidase (PPO), an enzyme abundant in ...
Generalized anxiety disorder affects millions, often trapping sufferers in cycles of fear and isolation that conventional medications barely relieve. At UCSF, neuroscientist Jennifer Mitchell is testing a pharmaceutical form of LSD called MM120, ...
Groundbreaking research published in The Lancet suggests that most people who believe they’re sensitive to gluten are actually reacting to other factors like FODMAPs or brain-gut dynamics. The study challenges the idea that gluten itself is the ...
King’s College London researchers discovered that parts of our DNA once thought to be “junk” can actually help destroy cancer cells. In some blood cancers, damaged genes trigger chaos in these DNA segments, leaving cancer cells vulnerable. ...

Latest Headlines

updated 12:56 pm ET