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At What Prescription Do You Become Legally Blind?

You may think it would be easy to know whether you should be classed as legally blind. After all, being unable to see beyond your nose, or relying on your glasses or lenses as a lifeline should give you a hint, right? But while these may be telltale signs that something isn’t right, things are rarely that simple – especially when it comes to your vision.

Our eyes are the second-most complex organ in our bodies, second only to our brains. This complexity means there are as many types and degrees of vision as there are colours we can see (that’s approximately 100 million!).

This can make knowing whether you would qualify as legally blind more difficult than you might expect.

Being Registered Blind in the UK

More than 2 million people in the UK live with some form of sight loss. This includes individuals with refractive errors such as myopia (short-sightedness), hyperopia (long-sightedness), and astigmatism. Around 340,000 of these are also registered as “legally blind” or “partially sighted”.

To be registered as legally blind or partially blind, you must undergo several tests with an eye specialist. This ensures you meet the Royal National Institute of Blind People (RNIB)‘s criteria for certification of blindness or partial blindness.

These examinations are designed to assess the sharpness and clarity of your vision (your visual acuity) and the quality of your visual field, including your peripheral vision. The results of these two tests determine whether you should be classified as legally blind.

If you score well on one test, the other aspect of your vision would have to be extremely poor for you to qualify as blind. For example, if you have good visual acuity, your visual field would need to be severely compromised. On the other hand, if you have all your visual field, your visual acuity would need to be extremely limited to meet the RNIB criteria for certification.

Are You Blind or Partially Sighted?

Knowing for yourself whether you would qualify as blind or partially sighted is no easy feat. Thankfully, the process of finding out is established and straightforward.

As mentioned above, your ophthalmologist will perform a number of tests, the first of which is the familiar Snellen Test. This test is used to assess your visual acuity. If you have ever been to an optician’s for an eye test, you will likely have had one before.

The Snellen Chart features rows of black letters that get increasingly smaller. Patients are asked to read these letters aloud until they can no longer distinguish them.

The standard level of visual acuity is 20/20 (or 6/6). This means that you can see/read at 20 feet (six metres) what someone with standard vision can see from 20 feet; this acts as the standard on which all other measurements are based.

If you are only able to read the first line of the chart, your visual acuity would be 6/60, meaning you can see at six metres what someone with standard vision can see at 60 metres.

To test whether you qualify as legally blind or partially sighted, you will also undergo a visual field test. During this test, the ophthalmologist will cover one of your eyes and ask you to focus on a target object. They will then ask you questions about what you can see on the far edges and periphery of your vision.

Both of these tests are performed while you wear your glasses to test your “best-corrected” vision.

Your Results

The results from your visual acuity and visual field tests will help your ophthalmologist determine whether you are severely sight-impaired or legally blind. This depends on whether your results fall into one of the following categories:

  • Visual acuity of less than 3/60 with a full visual field.
  • Visual acuity between 3/60 and 6/60 with a severe reduction of field of vision, such as tunnel vision.
  • Visual acuity of 6/60 or above but with a very reduced field of vision, especially if a lot of sight is missing in the lower part of the field.
The following categories are used to determine if you are sight-impaired or partially sighted:
  • Visual acuity of 3/60 to 6/60 with a full field of vision.
  • Visual acuity of up to 6/24 with a moderate reduction of field of vision or with a central part of vision that is cloudy or blurry.
  • Visual acuity of 6/18 or even better if a large part of your field of vision is missing. For example, a whole half of your vision is missing or a lot of your peripheral vision is missing.

However, you may not qualify as legally blind if you only have poor vision in one of your eyes, if your sight loss is temporary, or if you are currently receiving treatment that may improve your vision.

The Bottom Line

If you are concerned about the quality of your vision, or if you think you might be partially sighted, you should seek a referral from your GP or go directly to an expert ophthalmologist who can help determine your status.

This will provide you with peace of mind and clarity regarding your standard of vision. Moreover, once you are sure where you stand, it will be easier to explore potential treatment options. This process can be surprisingly positive, especially if you choose a clinic that can safely treat very high prescriptions.

If you’d like to learn more about our treatment options, get in touch with one of our friendly clinic coordinators. Alternatively,  Book a Consultation today.