Ask The Optician | Optical Centre Smarbuyglasses UK

What Prescription Is Legally Blind?

When visiting your optician or optometrist for an eye prescription, you may find yourself immersed in a new and unfamiliar world. While your eye doctor will walk you through it and try to explain as much as possible, you may find that you need particular answers about certain eye-related questions that you may find yourself encountering. One of those questions may be about the concept of legal blindness. 

Whether or not you are legally blind can affect a huge range of things, from your ability to obtain a driver’s licence or disability benefits. Because of this, it is important to understand whether your eye prescription is considered legally blind.


What Does Legally Blind Mean?

Before talking about which prescription is legally blind, it’s important to explore what legal blindness actually is. To put it simply, legal blindness is measured by looking at your central visual acuity (essentially how well you see what is in front of you) and your field of vision (how well you can see to the sides, above, and below you).

To test your vision, your optician will make you look at a Snellen chart - the familiar chart of mixed letters that you read from a distance of about 20 feet. When completing this test, you are considered legally blind if your vision is deemed to be ‘20/200’ or less. This means that if there is an object located approximately 200 feet away, you need to stand 20 feet away from it in order to see clearly. By contrast, a person with normal vision (20/20) can see said object clearly from 200 feet away. Your optician may also give you a visual field test in order to test your field of vision. During this test, you may be considered legally blind if your peripheral vision is about 20° or less.

Once you’ve taken these tests, you will want to take a look at your eye prescription. If your prescription is -2.5 or lower, this means that you are legally blind as visual acuity of -2.5 is equivalent to 20/200 vision. Coupons on