How to Perform a Visual Field Assessment in Low Vision

A visual field assessment is an important procedure that helps your optometrist learn more about the nature of your visual impairment and its impact on your daily life. It’s an essential step in determining the best treatment options for you, so understanding this test and how it works will be crucial to ensuring that your doctor gets the most accurate information possible. Here’s what you need to know about this vision test and how it’s performed!

What does Visual Field mean?

Visual field is a term used to describe how much of your surroundings you can see. The periphery, or visual field, refers to what we see outside of direct sight—at our sides and peripherally. What we see out of our peripheral vision isn’t as crisp and clear as what we see straight ahead, but it still provides meaningful information about our environment.

What is the Snellen chart?

The Snellen chart is used for visual field assessment. The distance is 20 feet. The letters on it are large, clear and vary from one another. 20/20 is a reference to what a person with average sight can see on an eye chart from 20 feet away. When a person is 20/40, it means that they have to move up (or closer to the chart) to 20 feet, to see what the average person can see at 40 feet. The larger the second number, the worse vision a person has. By looking at an eye chart and checking what you can see at various distances, your optometrist can better determine how much vision loss you have (or don’t have).

Why use eye charts?

The eye chart, or Snellen chart, is perhaps one of best-known tools for visual acuity assessment. The Snellen chart is used universally and can allow eye care providers to understand your visual needs and limits easily.

What is considered impaired vision?

There are many different kinds of vision impairment, and how well we see depends on several factors, including the part of our visual system that is damaged. Impaired vision is often used synonymously with low vision—the loss of best-corrected central visual acuity to 20/40 or worse. Our threshold for impaired vision was selected somewhat arbitrarily but with an eye toward clinical impact.

Are there different types of visual fields?

There are three main categories of visual field: central, peripheral and binocular. Central vision refers to what we see when we look straight ahead; peripheral vision refers to what we see on either side; binocular vision refers to what we see with both eyes together. At Gypsum Vision – we are happy to be using the Oculus Easy Field – which allows fast and effective testing of a full peripheral and central field.

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