The question of at what prescription one is legally blind isn't answered by a single number or diopter. Legal blindness isn't defined by a specific prescription power (like -8.00 or +6.00), but rather by visual acuity and visual field. Let's break down what that means.
What is Visual Acuity?
Visual acuity refers to the sharpness of your vision. It's measured using the Snellen chart (the chart with the big "E" at the top), expressed as a fraction (e.g., 20/20, 20/40). 20/20 vision is considered normal; you can see at 20 feet what a person with normal vision can see at 20 feet. 20/40 means you need to be 20 feet away to see what a person with normal vision can see at 40 feet – your vision is less sharp.
What is Visual Field?
Visual field refers to the entire area you can see when looking straight ahead. A restricted visual field means you can't see everything in your peripheral vision. This can be due to various eye conditions.
So, How is Legal Blindness Defined?
In the United States, legal blindness is defined as either:
- Visual acuity of 20/200 or worse in the better eye even with correction (glasses or contact lenses). This means that you can only see at 20 feet what a person with normal vision can see at 200 feet.
- A visual field of 20 degrees or less. This severely restricts your peripheral vision.
It's crucial to understand that a high prescription (like -10.00 or higher) can lead to legal blindness, but it's not the sole determining factor. Someone with a moderately high prescription might still retain sufficient visual acuity and field of vision to avoid being classified as legally blind. Conversely, someone with a lower prescription might still meet the criteria for legal blindness due to other factors affecting their visual acuity or field.
What are the different levels of visual impairment?
The definition of legal blindness sets a benchmark, but there are varying degrees of visual impairment. Someone might have low vision, requiring assistive devices, but not meet the criteria for legal blindness. The specific challenges faced depend on the individual's visual impairment.
How is legal blindness determined?
A comprehensive eye examination by an ophthalmologist or optometrist is necessary to determine legal blindness. They'll assess both visual acuity and visual field to determine if you meet the legal definition.
Can you still drive if you're legally blind?
This varies greatly depending on local laws and the individual's specific visual capabilities. Most legally blind individuals cannot drive, but exceptions are sometimes made depending on the type and extent of the visual impairment.
What are the resources available for the legally blind?
There are many resources available to support individuals who are legally blind, including assistive technology, rehabilitation services, and support groups. Contact your local vision rehabilitation agency or disability services to learn more about available resources in your area.
Remember, this information is for general knowledge and doesn't constitute medical advice. Always consult with an eye care professional for a proper diagnosis and treatment plan.
