What is a Visual Acuity Test?

A visual acuity test is an eye exam that evaluates how clearly you can see letters or symbols from a specific distance. It measures your ability to discern shapes and fine details, which is just one part of overall vision, alongside colour vision, peripheral vision, and depth perception.

Various tools can be used for these tests, such as the Unitech Vision Acuity Vision Chart, Unitech Vision Snellen Vision Chart, ECP Vision Drum, and Vision Drum. Retinoscopy is another method used to assess refractive errors in the eye. The test can be conducted by an optometrist, ophthalmologist, optician, technician, nurse, depending on the setting.

Visual acuity tests are risk-free, require no special preparation, and can be easily accessed through medical apps or medical equipment apps for improved accuracy and convenience.

Types of visual acuity tests

Two commonly used visual acuity tests are the Snellen Test and the Random E Test.

The most common types of visual acuity tests include:

Snellen Eye Chart

The Snellen test is what many think of when imagining a vision test. It’s a chart with rows of letters, starting large at the top and getting progressively smaller as you go down. You’ll be asked to read the rows until you can no longer make out the letters. Some eye care professionals use Snellen charts displayed on a wall or projected onto a screen.

Random E Chart

The random E test is similar to the Snellen chart, but instead of letters, it uses only the letter "E," which is rotated and placed in different directions. You’ll identify the direction the "E" is facing—up, down, left, or right—as it gets smaller down the chart.

Dynamic Visual Acuity Test

In this test, your head is moved back and forth while you focus on a target. It checks how well your eyes stabilize during motion and how well you can maintain vision clarity as your head moves.

Pinhole Visual Acuity Test

This test helps diagnose myopia (nearsightedness). You’ll cover one eye with a paddle that has small holes. Looking through the holes with the covered eye, you’ll read the chart to check if your vision improves, helping determine if nearsightedness is the cause of poor vision.

Visual Acuity Tests for Children

Pediatric visual acuity tests may use pictures or symbols instead of letters. For younger children, tests like the Cardiff visual acuity test or matching symbols to a Snellen chart can be used to evaluate vision.

Visual Acuity Test at Home

Online and printable vision charts from ECP and Unitech vision are available for basic at-home visual acuity checks. These charts, such as the Snellen Chart, can be printed and used from a distance of 10 to 20 feet. While they offer a convenient way to check vision, they should not replace professional eye exams for accurate diagnosis and prescription.

Visual Acuity Test for Children

Early vision screening in children is crucial for detecting potential vision problems early, which can significantly impact learning and development. Common issues include amblyopia (lazy eye), where one eye doesn't develop proper vision, and strabismus (crossed eyes), where the eyes do not align properly. Early detection and treatment of these conditions can help prevent long-term vision problems.

Visual Acuity Test for Drivers

Vision requirements for driving typically include a minimum visual acuity of 20/40 in at least one eye, with or without corrective lenses, and the ability to distinguish between red, green, and amber traffic lights. To prepare for a driver's vision test, make sure your eyes are healthy and you have the necessary prescription glasses or contact lenses if needed. It’s also a good idea to schedule a comprehensive eye exam to ensure optimal vision before taking the test.

Preparing for the Visual Acuity Test

To prepare for a driver's vision test, make sure to wear your regular eyeglasses or contact lenses if you need them for clear vision. Avoid wearing new or unfamiliar eyewear on the day of the test. Ensure your eyes are well-rested, and if you’re due for an eye exam, it’s a good idea to get one before the test to address any vision concerns.

How does a visual acuity test work?

1. Stand or sit about 20 feet away from the chart or screen.
2. Cover one eye, usually with a hand or a paddle.
3. Read the chart, starting with the largest row of letters or symbols.
4. Continue reading smaller rows until the letters or symbols become unclear.
5. After testing one eye, you’ll switch and repeat the process with the other eye.

If the chart becomes difficult to read, it’s okay to guess. Let your eye care professional know if the letters become blurry, and avoid squinting or straining your eyes. The goal is to accurately assess your vision, so don’t worry about trying to "pass" or "fail" the test.

If you already wear eyeglasses or contact lenses, the test may be repeated with and without your corrective lenses to check both uncorrected and corrected vision.

Conditions Affecting Visual Acuity

Common conditions that can affect visual acuity include:

Nearsightedness (Myopia): Difficulty seeing distant objects clearly.

Farsightedness (Hyperopia): Trouble focusing on close objects.

Astigmatism: Blurred vision caused by an irregularly shaped cornea.

Cataracts: Clouding of the eye's lens, leading to blurry vision.

Glaucoma: Increased eye pressure that can damage the optic nerve and affect vision.

These conditions can impact your ability to see clearly and may require corrective lenses or other treatments.

Tips for Good Visual Acuity

To maintain healthy vision, it's important to adopt a healthy lifestyle. Eating a balanced diet rich in vitamins and nutrients, such as leafy greens, carrots, and fish high in omega-3s, can support eye health. Regular exercise improves blood circulation and helps prevent conditions like diabetes, which can affect your eyes. Additionally, protect your eyes from harmful UV rays by wearing sunglasses with UV protection when outdoors to reduce the risk of cataracts and other eye issues. These habits can help preserve your vision for the long term.

Interpreting Visual Acuity Test Results

Visual acuity scores like 20/20 or 20/40 measure how well you can see at a specific distance compared to the average person.

20/20: This means you can see clearly at 20 feet what a person with normal vision can also see at 20 feet. It’s considered perfect or normal vision.

20/40: This means you can see at 20 feet what someone with normal vision can see at 40 feet. It’s a bit less sharp, but still good for many everyday activities, like driving.

A smaller second number, like 20/10, means better-than-average vision. A larger number, like 20/80, means vision is less sharp and might require corrective lenses.