- How it Works
October 4, 2017
20/20 vision is a term that is used a lot these days to describe anything from eyesight to TV shows and current events. While we all know “seeing 20/20” is a good thing, you may not know exactly what it means when it’s used to describe your eyesight.
The term 20/20 describes normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance by the human eye. If you have 20/40 vision, you can see clearly at 20 feet what should be normally be seen at the distance of 40 feet by the human eye (meaning that your eyesight is not as sharp).
When you have an eye exam, visual acuity is one of the first tests that your eye doctor will perform, usually done with an eye chart of letters or other characters, called a Snellen Chart. The acuity test is one of the most important gauges of your vision, and additionally, your overall eye health.
When doctors check your visual acuity, they test your vision one eye at a time and then with both eyes together. Since acuity is a gauge of how sharp we can see, each eye is tested separately at first. Whether you can see 20/20 out of each eye or both eyes mean different things:
If one of your eyes cannot see 20/20, it means that you might have a vision problem and could benefit from wearing glasses. In some instances, not being able to see 20/20 can be an indication that there is a health issue with your eye. Glaucoma, macular degeneration, and cataracts are all common eye health issues that may cause a change in visual acuity. Additionally, diabetes, high blood pressure, and high cholesterol can also impact our ability to see clearly.
In young children, not being able to achieve 20/20 vision in one eye can be a sign of amblyopia, often called a “lazy eye”. Amblyopia may be hard to detect if each eye is not tested separately because children may not recognize that one of their eyes is blurry. If amblyopia is not treated in time, that eye may not ever be able to achieve 20/20 vision. If one eye cannot see 20/20, depth perception (3D vision) decreases, which can affect a person’s ability to play sports, drive a car, fly a plane, or even have a certain career.
Separate eye testing (monocular testing) is, therefore, critical in knowing the visual status of each eye.
Checking both eyes together (binocular testing), however, is more of a screening test and less specific than monocular testing. When you get your driver’s license, you have to have a minimum visual acuity in order to drive without corrective lenses. Almost all states base the minimum vision to drive without vision correction on the binocular test.
As you can see, visual acuity testing is extremely important for many reasons. Numerous studies and research have proven the benefits of getting our vision checked regularly. School districts, pediatricians, family physicians, and even sports teams routinely test visual acuity. If problems are discovered, referrals to eye care professionals are made for further evaluation. Hopefully, not seeing 20/20 is simply about wearing corrective lenses and not a more serious health issue. Getting a comprehensive eye exam every year, which includes an eye health check, is strongly recommended.
In summary, check your visual acuity often, report concerns to your doctor, and even if there are no changes in your vision, an annual eye health exam is still an important part of caring for your eyes.
The Insight from EyeQue is an at-home visual acuity test that works on adults and children. Our vision screening tool offers the most convenient way to tets your visual acuity from home between eye exams.
Dr. Jay Kaufman is member of EyeQue’s Optometry Advisory Board. He graduated with his Doctor of Optometry degree from Nova Southeastern University, College of Optometry, in Florida in 1994. He graduated from the University of California, Santa Barbara with a degree in Communication
Studies in 1989. Dr. Kaufman is in private practice in the Seattle area where he specializes in family eye care, contact lens fitting, ocular disease detection, and LASIK surgery co-management.
Dr. Kaufman is a Board Certified Optometrist licensed to treat many ocular conditions using the latest drug therapies. His background includes working in Ophthalmology practices, Laser Refractive Surgery clinics, nursing homes, and his own practice where he has seen patients for the last 15 years. Dr. Kaufman has combined his love of Optometry with his studies in Communications to be an active and well-respected member of his community. He has helped school-age children with vision and sports screenings and has served on the Board of his local Chamber of Commerce.
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