Many people incorrectly believe that having 20/20 vision is the same as having “perfect” eyesight. However, this term is simply a measure of your visual acuity. Someone with 20/20 vision can still have other eyesight problems.
How Is Visual Acuity Measured?
Eye exams often involve standing in front of an eye chart and reading a line of letters while covering one eye at a time. The eye charts we use today were developed by Dutch ophthalmologist Herman Snellen in 1862. This is why eye charts are sometimes called Snellen charts, and visual acuity fractions like 20/20 are known as Snellen fractions.
What are the Variations on 20/20 Vision?
The term 20/20 means you can see clearly at 20 feet what you would expect to perceive at that distance. Having 20/20 vision may be the goal, but it’s not the best vision you can have.
If you can discern the line of letters below the 20/20 line on a Snellen chart without moving closer, you have 20/15 vision. This means you can see at 20 feet which someone with normal vision can only discern if they stand 15 feet away. 20/10 vision is also possible, indicating double the visual acuity of someone with 20/20 vision.
Clarity of vision can go the other way as well. For instance, 20/40 vision means you must get within 20 feet to see letters that someone with normal vision can read from 40 feet back. If you can only read the large “E” at the top of an eye chart, you have 20/200 vision.
Can Visual Acuity Vary by Distance?
Yes. Some people have difficulty focusing on objects far away. This type of refractive error is called myopia (nearsightedness). Others can see things at a distance but struggle to focus on up-close objects. This is called hyperopia (farsightedness). Similarly, presbyopia is the gradual decline in up-close visual acuity that happens naturally with age. Other conditions, such as astigmatism or eye disease, can also affect a person’s clarity of vision.
What Else Contributes to Good Vision?
Besides visual acuity, here are some other important visual skills that are needed to see clearly:
- Eye coordination
- Peripheral awareness
- Depth perception
- Focusing ability
- Color vision
- Ability to track moving objects
- Ability to discern objects similar in brightness to their background
Do I Need an Eye Exam?
Whether you have trouble seeing up close or far away, an optometrist can prescribe corrective eyeglasses or contact lenses to improve your ability to see from all distances. Even if you have 20/20 vision, regular eye exams are still essential to check your eye health, monitor changes in eyesight, and diagnose diseases like glaucoma and cataracts before symptoms appear. Boulder Eye Surgeons offers comprehensive eye care, including routine eye exams. We also specialize in medical eye care, using the best technology and most advanced techniques to help you achieve and maintain clear vision. To schedule an appointment with our professional, compassionate eye doctors and surgeons, please contact us today.