Having a 20/20 vision means having normal vision. It means the person can see things clearly from a 20feetdistance as an average person would see from the same distance.
A 20/20 vision is a way to measure visual acuity. Visual acuity is a medical term for the clearness or sharpness of vision. This is a simple test done by an optometrist or at an eye doctor’s (ophthalmologist) office to check eyesight. The test uses an eye chart called Snellen vision testing chart in which there are numbers. The person will be asked to try reading the numbers from a 20 feet distance. The result of this test could mean the following:
- A 20/20 vision means that a person has an average or normal vision.
- 如果一个人有20/30视力,这意味着他们need to be 20 feet near to the object to see it clearly when most people can see the same from 30 feet. This means that their vision is worse than average.
- If a person has a 20/15 vision, they have a vision that is sharper than average, and it is normal to have one. It means they can see an object clearly that is placed 20 feet away when most people will need to be 15 feet near to the object to see it.
Even if a person does not have a 20/20 vision, they shouldn’t worry much. Glasses or contact lenses can help correct the vision to 20/20.
大约35每100个成年人中有20/20的视力without using glasses, contact lenses, or have any eye surgery. Also, 75 percent of adults with less than 20/20 vision can have 20/20 vision after correction with glasses, contact lenses, or eye surgery. People are termed “legally blind” if their vision with glasses or contacts is 20/200 or worse.
What causes your vision to be less than 20/20?
Many factors can affect the clarity of vision. These include conditions, such as
- Myopia(nearsightedness)
- hyperopia(farsightedness)
- Presbyopia(inability to focus on close objects due to old age)
- Astigmatism(imperfect curvature of the eye’scorneaorlens)
- Eye diseases
When to have an eye checkup
Even if a person has healthy eyes and good vision, the American Academy of Ophthalmology recommends having a complete eye exam by an ophthalmologist at 40 years of age. This is the age when眼睛的问题are most likely to start. If suffering from health issues, such asdiabetesandhypertension(high blood pressure), get the eye checkup done earlier before turning 40 years old.
- People 60 years of age or older must get an eye checkup at least once every one to two years.
- If a child is old enough to read with a vision chart, the academy also recommends testing the child’s vision. Ideally, it should be checked between three to five years of age and once every year thereafter.
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References
Vitale S, Ellwein L, Cotch MF, Ferris FL 3rd, Sperduto R. Prevalence of Refractive Error in the United States, 1999-2004. Arch Ophthalmol. 2008;126(8):1111-1119. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2772054/
Vimont C. What Does 20/20 Vision Mean? American Academy of Ophthalmology. https://www.aao.org/eye-health/tips-prevention/what-does-20-20-vision-mean
Vimont C. What Does 20/20 Vision Mean? American Academy of Ophthalmology. https://www.aao.org/eye-health/tips-prevention/what-does-20-20-vision-mean
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