The Visual Acuity Test

eye exams lethbridge

Everything You Need To Know

What is the Visual Acuity Eye Exam?

The visual acuity test is used to determine the smallest letters you can read on a standardized chart (also known as the Snellen chart) held 20 feet away.

This eye exam measures the clarity of your vision (i.e. your ability to discern the shape and details of objects.)

This is just one factor of your overall vision. Other factors include:

  • Color vision
  • Peripheral (side) vision
  • Depth perception
  • Focusing ability

Only a comprehensive eye exam conducted by a qualified optometrist or ophthalmologist can test all these factors and evaluate your overall visual ability.

How is the test performed?

This test can be done in any health care professional’s office, in a school or a workplace.

During the eye exam, you will be asked to:

  • Remove your eyeglasses or contact lenses
  • Sit 20 feet away from the eye chart
  • Cover one eye with your palm or a small paddle
  • Read out loud the smallest line of letters you can see on the chart.

If you aren’t certain of the letter, you may guess as this is still an indication of your ability to decipher shapes. The test is done on each eye, one at a time. If required, you may be asked to repeat it while wearing your eyeglasses or contact lenses.

How to prepare for the visual acuity test

There is no special preparation necessary for this test.

Book an eye exam today and one of our eye doctors will be happy to help!

Why is the test performed?

The visual acuity test is part of a routine eye examination or a general physical exam, especially if the patient has experienced a change in or problem with their vision.

For children, the exam is often used to screen for potential visual problems such as  amblyopia (lazy eye). If detected early, such problems can often successfully be corrected. If left untreated, problems have the risk of leading to permanent vision loss.

At Lethbridge eye clinic, our Optometrists perform eye exams specially designed for children to accurately assess the health of their eyes, even if they can’t read yet.

Results of the visual acuity test

Visual acuity is expressed as a fraction.

  • The first number refers to the distance you stand from the chart. This is usually 20 feet.
  • The second number indicates the distance at which a person with normal eyesight can read the same line you read correctly.

Any abnormal results could indicate that you need eyeglasses or contact lenses. Or it could mean that you have an eye condition which requires further evaluation by an eye doctor.


20/20 is considered normal vision.

If you have 20/40 vision, this means that the line you correctly read from 20 feet away can be read by a person with normal vision from 40 feet away

(This would be an indication of nearsightedness)

At Lethbridge eye clinic, our qualified optometrists provide comprehensive services to ensure the health and safety of your vision. These include:

To learn more about our extensive services or to book an appointment today, contact our eye clinic at 403-327-4166

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