UAB Medicine News
What It Means to Be Legally Blind, and How UAB Can Help
We all know what it means to be blind. You can’t see. But is it that simple? Did you know that there are degrees of blindness? According to the legal definition, a person can have some vision and yet be considered legally blind. This article explores that definition and highlights some of the resources and services UAB offers to people who are legally blind.
Legal blindness is not a medical term but a governmental one that can determine whether a person is legally entitled to certain disability and financial benefits or subject to certain restrictions, such as being prohibited from driving an automobile. There are two different aspects of vision that determine legal blindness: decreased visual acuity (sharpness) and an extremely narrow field of vision. You can have perfect visual acuity but a narrow field of vision (or a normal field of vision with low visual acuity) and still be considered legally blind.
Visual acuity is how far you can see clearly. This is measured with the Snellen Visual Acuity Test, which is the traditional eye chart that features letters of different sizes.
Normal visual acuity is rated as 20/20 vision. That means the person can see things 20 feet away as clearly as the average person can see the same things at 20 feet away. As visual acuity gets worse, that second number gets bigger. For example, 20/40 vision means a person can see things clearly at 20 feet away that the average person can see clearly at 40 feet away.
So what is the magic number that constitutes legal blindness due to decreased visual acuity? According to the U.S. government, a person’s vision must be at least 10 times worse than the average person, measured by looking directly at something with both eyes. This translates to 20/200 vision or worse on the Snellen Visual Acuity Test. A person cannot be legally blind in one eye, as legal blindness pertains to overall vision with both eyes.
It’s important to understand that even if a person’s vision is 20/200 or worse without glasses or contact lenses, he or she is not considered legally blind if the vision impairment is correctable with glasses or contacts.
Visual field is defined by measuring how far away a person can see using his or her peripheral (side) vision. The visual field can be reduced in many different ways. It can occur in one or both eyes, and it also can affect the top and/or bottom (rather than the sides) of the visual field. In some cases it affects the visual field in every direction.
The average person has a field of vision of approximately 180 degrees. This means that when they look straight ahead with both eyes open, they can see what is directly in front of them, what is to the left and right, what is above them, and down to the ground. People who are legally blind due to a constricted visual field have 20 degrees or less of their field of vision remaining in their better eye. This is known as tunnel vision.
Overcoming Visual Limitations
Dawn DeCarlo, OD, is an ophthalmologist at UAB Callahan Eye Hospital and director of the UAB Center for Low Vision Rehabilitation. She says most of her patients who are legally blind want help to improve their ability to read – enough to allow them to pay bills, try a new recipe, and perform other day-to-day tasks. Along with fellow ophthalmologists Marissa Locy, OD, and Christopher Lee, OD, she helps patients better perform daily activities despite vision problems. They provide adaptive equipment and work with occupational therapists to help patients develop new strategies to overcome limitations imposed by their vision impairment.
For people who are legally blind due to low visual acuity, Dr. DeCarlo recommends different types of magnification to help her patients. These include things such as a traditional handheld magnifying glass, as well modern takes on this common device. Today there are lighted magnifiers, some that are on stands, some that can be mounted on the head, dome-style magnifiers, and even video magnification technology that projects an image on a computer screen or to a device that is worn in front of the eyes.
For those whose legal blindness is due to a constricted visual field, Dr. DeCarlo says occupational therapy and orientation and mobility training can be helpful. The UAB Center for Low Vision Rehabilitation tailors its therapy in these areas to each individual patient, with the goal of achieving greater independence. Options may include the use of a cane, modifications to the home or living/work spaces, training in using remaining vision more efficiently, practicing safety to avoid falls or accidents, and other approaches.
Click here to learn more about the UAB Center for Low Vision Rehabilitation, or call 205-488-0736 to make an appointment.
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