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Home » Eye Health » Eye Exams » Common Tests » Snellen Chart

Snellen Chart

Hopefully by now, we’ve all seen one. The projected or wall-mounted Snellen eye chart, usually topped by the big letter “E”, is a common visual acuity test used to measure your sharpness of vision at multiple distances.
 
Arranged as a pyramid of sorts, the letters in the Snellen chart are specifically chosen and arranged to test your sharpness and clarity of vision at a baseline distance of 20 feet. During a visual acuity test, the Snellen eye chart is viewed as a projection, or mounted on a wall.
 
Handheld versions of Snellen charts are used for testing near vision as well.
 
By viewing or reading each line from top to bottom (with one eye covered at a time), your eye doctor can gain a general approximation of the quality of your visual acuity, or sharpness. Where a line of characters begin to become difficult to see is the approximate measurement of your vision.
 
The Snellen chart serves as a beginning—not an end—to a comprehensive eye examination.

What does “20/20” vision mean?

Snellen charts help to determine a baseline for your vision in each eye—a baseline typically measured against “20/20” vision. This means when you are 20 feet away from an object, you can comfortably see details that most people with normal vision can also see at 20 feet distance.
 
If you have 20/30 vision, that means what you see comfortably at 20 feet, can be seen by a person with “normal” vision at 30 feet. Your vision is weaker, in other words.
 
Conversely? In the rare instances where vision may test better than normal on a Snellen chart, a value of 20/10 vision means that you can see clearly from a distance of 20 feet, what a person with normal vision sees well at a distance of 10 feet. Make sense?
 
In fact, if you look closely at a Snellen eye chart, you’ll see the vision values associated with measuring your vision on the right or left side of each line of characters.
 

Special thanks to the EyeGlass Guide, for informational material that aided in the creation of this website. Visit the EyeGlass Guide today!

Dear Patients,

Dr. Lewis Eye Care has made the difficult choice to temporarily close due to the COVID-19 virus pandemic based on the recommendation of the CDC. We cannot perform eye exams while maintaining social distancing, so continuing to see patients at this time could contribute to the spread of the virus.

Our initial plan had been to reopen Monday April 6th. However, as we get closer to that date it is becoming apparent that we may have to be closed for a longer, indefinite period of time.

If you are having an urgent eye health issue, there are some clinics in our area that are seeing patients for emergencies during shorter business hours. You should call ahead to those offices before going to their clinic, as their availability might change day by day. Those clinics could include Vancouver Eye Care at 360-823-2020, Peace Health Medical Group Eye Care at 360-514-7210, and Vancouver Clinic in Salmon Creek at 360-882-2778.

If you need a glasses or contact lens prescription emailed to you from our office, click on the Contact Form link, type in your name, email, and what you are requesting, and we will email you the information you need as soon as we can.

Thank you for your understanding, and please stay healthy during this difficult time.

Sincerely,

Dr. Scott Lewis, OD