What is Visual Acuity? Understanding the Sharpness of Your Sight
About 35% of people have 20/20 vision. However, this isn’t the same thing as perfect sight. You may be surprised to learn that even people with 20/20 vision can experience certain visual issues. So what does having 20/20 vision really mean? This ratio is actually a measurement of visual acuity. It offers insight into how clearly and sharply you see items at a certain distance. It doesn’t mean, however, that you have perfect vision.
Learn more about visual acuity and why it’s only one part of establishing eye health.
What is 20/20 Vision?
If you have 20/20 vision, your visual acuity is considered typical. It means that you can clearly see an object that is 20 feet away from you.
The first number in “20/20” represents how far you’re standing from the object. It’s always 20, since this particular vision test always uses 20 feet as a reference. The second number refers to how far a normal person would have to stand from the object to see it as clearly as you do.
For example, if you have 20/10 vision, you have above-normal visual acuity: You can see at 20 feet what a typical person sees at 10. With 20/40 vision, on the other hand, you can see at 20 feet what a typical person can see at 40.
Measuring Visual Acuity
To test your visual acuity, professionals rely on a few different charts, starting with the Snellen chart. It’s the most common one you’ll come across when getting an eye exam. The Snellen chart includes rows of capital letters that get progressively smaller.
There is also the Random E chart, which was made as an alternative to the Snellen one. This chart can be helpful for individuals who struggle with communication or letter identification. It has progressively smaller Es that face left, right, up, or down. During the exam, one must point in the direction that each E faces.
Some charts focus on picture recognition to assess the visual acuity of small children. These charts use recognizable shapes and figures instead of letters.
To test your visual acuity, you will need to stand 20 feet away from the chart in question. If the room isn’t large enough to accommodate this, mirrors will be set up to provide the same effect. Without using glasses or contacts, you’ll try to read the letters, starting at the top.
Because your visual acuity could be different in each eye, your doctor will typically ask you to cover one eye at a time. The lowest row you can read determines your acuity score.
Beyond Visual Acuity
Visual acuity is not the only measurement that matters when it comes to your eyesight.
Depth Perception
One factor that acuity doesn’t address is depth perception. This ability is essential for navigating the world because it allows you to understand an object’s size and its distance from you.
With poor depth perception, you may struggle to walk without hitting things, and you might have trouble grasping objects. Depth perception is also linked to balance and coordination.
People with lazy eyes, crossed eyes, or poor overall vision can experience difficulties with visually judging distance and movement. Your optometrist can use a specialized test to assess whether you have good depth perception.
Peripheral Vision
Peripheral vision refers to your ability to see objects that are out of your direct line of sight. If you have good peripheral vision, you can be more aware of your surroundings and detect movement out of the corner of your eye. On the other hand, someone who can see only what’s directly in front of them is said to have tunnel vision.
To assess your peripheral vision, your doctor will conduct a visual field test. You’ll keep your vision fixed on a central point, usually some form of light. Then, you’ll indicate when you see other lights that flash centrally and peripherally within your field of vision.
Contrast Sensitivity
Contrast sensitivity is your ability to detect subtle differences in lightness and darkness. Good contrast sensitivity means that you can more easily see objects that don’t stand out from their backgrounds. This ability is essential for driving at night, recognizing faces, navigating stairs, and reading.
To test your contrast sensitivity, your doctor can use the Pelli-Robson chart, which has letters or patterns in different degrees of contrast. This test allows optometrists to gauge whether you’re at risk of developing cataracts or other vision issues.
Eye Coordination
Eye coordination refers to how well your eyes work together to focus on a single point and provide a clear, three-dimensional image. Good eye coordination is vital for performing tasks that require depth perception and hand-eye coordination, such as catching a ball. Even writing can be much more difficult if you have weak eye coordination.
To test your eye coordination, your doctor might use a near point of convergence exam. This exam involves moving a light closer to your nose and asking you to state when you see it get blurry.
Protecting Your Vision With Regular Eye Exams
Visual acuity is essential for managing everyday life, but it’s not the only measurement that counts. Even if you have 20/20 vision, you could still develop sight problems that impact your quality of life and put you at risk when engaging in activities like driving. By getting regular eye exams, you can catch and address these problems quickly.
Would you like to learn more about protecting your vision? Looking Glass Optical can help. Contact our team of experts to schedule a consultation.
Share