Many may confuse blindness with legal blindness. They can actually be quite different. Complete blindness indicates that a person is unable to see or discern any images whereas people who are legally blind are capable of seeing images albeit very unclear. Nevertheless they are unable to meet the minimum legal requirements needed for safe vision standards, most especially for driving purposes. According to the National Federation of the Blind, approximately 1.3 million people considered legally blind in 2009 in the United States.
There are different types of legal blindness. The two most prominent ones being caused by reduced visual acuity and the other caused by a reduction in peripheral vision or field of vision restriction. Each of these types of legal blindness types are tested using different methods. For instance, for central visual acuity the Snellen Visual Acuity Test is used whereas for peripheral visual acuity the Visual Field Test is used.
For reduced central vision legal blindness is defined as scoring 20/200 or less on the Snellen visual acuity test. This indicates that a person suffering from visual blindness can only see letters at a distance of twenty feet on the Snellen Eye Chart whereas a normal person would see the same letters at 200 feet. However, if the use of corrective contact lenses or glasses can be used to improve a person's vision to a value above 20/200, or if only one eye is legally blind but not the other, then the person is not considered to be legally blind. Below is an illustration that approximates what reduced central visual acuity levels would look like.
To be legally blind due to reduced peripheral vision a person would have to demonstrate that their field of vision is restricted to 20 degrees or less. A normal person's field of vision all most extends to 180 degrees horizontally and 135 degrees vertically. This test is incredibly important in diagnosing legal blindness due to the impact that a reduced field of vision may have on daily tasks such as driving. Here is another illustration depicting a visual approximation of a field of vision blindness.
Legal blindness can be caused by many different factors. The most common causes are age-related macular degeneration, diabetic retinopathy, cataracts, and glaucoma. Some of these conditions such as glaucoma and cataracts can be treated and cured if diagnosed in time, however other disorders, such as macular degeneration, currently do not have any available cure.
Being legally blind directly impacts a person's quality of life restricting them from participating in such activities that many take for granted such as driving. Adjusting to this type of lifestyle can be trying and difficult, however the United States Government's Social Security Administration along with many non-government funded organizations provide benefits and assistance to those that qualify as legally blind. These services are specifically put in place to aide those who suffer from this disability. They provide the required support system and resources needed to transition and adapt as comfortably as possible to this new way of life.
Legally blind vision can drastically affect a person's way of life ranging from increased dependency on transportation to career limitations due to visual impairment. However, thanks to government subsidized programs and altruistic organizations a support system exists to help those suffering from this disability. If you or someone you know suffers from any of the above legally blind vision symptoms consult an eye doctor who can better assist you in the diagnoses, treatment and the development of a course of action for the future.
Legally Blind | All About Vision
Blindness and Low Vision | National Federation of the Blind
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