Blindness refers to an absence of vision or a loss of vision that tools such as glasses or contact lenses cannot correct. Legally blind is a term that the government uses to describe a person with vision below a certain measurement.
A person who is completely blind is unable to see anything, while a person who is partially blind or has a visual impairment may have limited vision.
In 2015, an estimated
In some cases, a person is born blind. In other cases, a person becomes blind or develops a visual impairment due to a condition, eye trauma, factors relating to aging, or cataracts.
This article will define blindness and visual impairments, discuss different types of visual impairment, and see which government benefits and treatment options are available.
According to the
Visual acuity refers to the clarity of a person’s vision. To test a person’s visual acuity, an eye care professional may ask them to read letters on a Snellen chart. The Snellen chart contains several lines of letters that start large and get smaller with each line.
A Snellen visual acuity of 20/20 is what eye professionals consider normal. This means that a person with 20/20 vision can see what an average person sees when standing 20 feet away from an object.
However, legally blind people will have a Snellen visual acuity of 20/200, meaning that at 20 feet, they can see objects that most people are able to see clearly from 200 feet.
Some people may assume that the term blindness refers to a complete lack of vision, but depending on the severity, some legally blind people may still retain some vision.
The American Foundation for the Blind state that there is no exclusive definition of visual impairment. However, there are different levels of classification based on the severity of the impairment.
The following sections will discuss these levels in more detail.
Moderate visual impairment
People with a moderate visual impairment will have a Snellen visual acuity of 20/70 to 20/160.
Severe visual impairment
A person who has a severe visual impairment will have a Snellen visual acuity of 20/200 to 20/400.
Alternatively, an eye doctor may regard someone as having a severe visual impairment if they have a visual field of 20 degrees or less. The visual field is the area a person can see without moving their eyes to the left or right.
Profound visual impairment
Profound visual impairment occurs when a person has a visual field of 10 degrees or less or a Snellen visual acuity level of 20/500 to 20/1000.
The Iowa Department for the Blind define a person as being functionally blind when they have to use alternative techniques to perform daily tasks that people typically perform with sight.
Some alternative techniques may include:
- using braille to read a book
- using the audio description option on the television
- using a guide dog to go out for walks or shopping
- using computer software to read the contents of the page out loud
Others may use the term functional blindness to refer to any visual deterioration that occurs without any obvious change or disease affecting the visual system.
There are different types of blindness and visual impairment, each with their unique effect on the visual system.
Some of these include:
Central vision loss
A person with central vision loss is unable to see fine detail. This compromises certain abilities, such as facial recognition and reading, as they must rely on only their peripheral vision for sight.
There are many conditions associated with central vision loss, such as:
- age-related macular degeneration (AMD)
- diabetic retinopathy
- macular edema
- macular hole
- macular pucker
Tunnel vision refers to a loss of
Tunnel vision may be temporary or permanent. For example, according to the American Migraine Foundation, some people with migraine may develop temporary tunnel vision.
A blind spot, or scotoma, is an inability to see an object in various parts of the visual field. In some people, this may appear as darkness, a bright light, blurriness, or flickering.
Like tunnel vision, blind spots may occur temporarily with some types of migraine.
A person with total blindness is unable to see anything. In some cases, this is referred to as no light perception (NLP).
However, some totally blind people may still be able to see light colors or movement. It is rare for a person to experience total blindness.
A study that looked at three completely blind participants with NLP found that their brains were still able to detect the presence of
If a person is blind or has a visual impairment, they may be able to receive some benefits through the Social Security Administration (SSA).
The SSA say that people with blindness or a visual impairment may qualify to receive benefits under two programs: the Social Security Disability Insurance program and the Supplemental Security Income program.
As the SSA assess benefits on a case-by-case basis, a person will need to contact Social Security directly to establish whether or not they qualify and what the programs offer.
Treatments vary depending on the cause of the blindness or visual impairment. However, in some cases — such as with retinal degeneration disorders — there is currently no cure.
Some causes of blindness or visual impairment that do have available treatments include:
- Diabetic retinopathy: If the cause of visual impairment is diabetic retinopathy, treatment may help stop it from
worsening. However, it cannot cure any existing damage. This treatment may involve receiving injections into the eye, trying laser treatment, or undergoing eye surgery.
- AMD: There are two types of AMD: dry and wet. If a person has dry AMD, there is no available treatment. However, if a person has wet AMD, treatments may consist of regular injections or a treatment called photodynamic therapy.
- Cataracts: Cataracts cause the lens of the eye to become cloudy, which may affect vision. A person with severe cataracts may require
surgeryto save their vision.
People may think that being legally blind refers to total blindness, but the U.S. has legal definitions for varying degrees of blindness. This includes vision loss that, even with correction, may require assistance in performing certain tasks.
The government will consider a person legally blind if they have a visual acuity of 20/200 or less. If a person is legally blind, they may be eligible to receive government assistance.