Vision Impairment definition: What about Strabismus?

Traditional Snellen eye chartIt’s pretty easy to define Vision Impairment. Just grab your dictionary and look up the words “vision” and “impair.”
Vision: The act or power of sensing with the eyes; sight.
Impair: To make or cause to become worse; diminish in ability, value, excellence, etc.; weaken or damage.

Permit me to offer my simple definition of Vision Impairment, based upon our defining source, the dictionary:

Vision Impairment is a state in which the act or power of sensing with the eyes (sight) is worse than optimal; diminished in ability, value, or excellence, etc.; weakened or damaged.

According to the World Health Organization, as quoted in the U.S. Government’s Agency for Healthcare Research and Quality, to have even a moderate vision impairment a person’s best corrected visual acuity must be less (worse) than 20/60. This 20/60 standard has been, and still is to a large degree, the defining standard for most of the U.S. Government’s publications and mandates.

The U.S. Government Centers for Disease Control and Prevention (CDC) starts it’s What is vision impairment? item a little more reasonably:

Vision impairment means that a person’s eyesight cannot be corrected to a “normal” level. Vision impairment may be caused by a loss of visual acuity, where the eye does not see objects as clearly as usual. It may also be caused by a loss of visual field, where the eye cannot see as wide an area as usual without moving the eyes or turning the head.

The CDC’s item goes on to cite the definitions offered by WHO and mentions the U.S.’s category of legal blindness, then continues to add a slightly more comprehensive view of visual acuity:

Visual acuity alone cannot tell you how much a person’s life will be affected by their vision loss. It is important to also assess how well a person uses the vision they have. Two people may have the same visual acuity, but one may be able to use his or her vision better to do everyday tasks.

I felt the CDC’s item was vague, but it is improved from the standards of strict adherence to 20/60 being the only criteria for Vision Impairment.

The American Academy of Ophthalmology adheres to the WHO’s 20/60 definition of Vision Impairment, but it does, thankfully, offer some concessions for other vision problems as well: According to the AAO, the definition of vision impairment is this: “If your vision with eyeglasses or corrective lenses is 20/60 or worse, you are considered visually impaired. Limitation of side vision, abnormal color vision, or presence of double vision in one eye also may determine visual impairment.”

The Optometrists Network goes much further, defining Vision Impairment to include Binocular Vision Impairment caused by Strabismus. Here is what The Optometrists Network says:

A binocular vision impairment is any visual condition that results in partial or total loss of stereoscopic vision and binocular depth perception….

Some binocular disabilities are easily noticed by others, such as conditions where both eyes obviously don’t aim in the same direction. These conditions are commonly referred to with terms like “cross-eyed”, “wall-eye” or “wandering eye”. Some of medical terms for these misalignments of the eye are strabismus, esotropia, exotropia….

Some binocular disabilities are not detected because the turning or straying of the eye(s) is not obvious or consistent. Some eye turns are intermittent (they come and go) and are not easily noticed by the untrained observer.

The Optometrists Network then goes on to promote the importance of early detection and intervention.

In spite of these improving trends, many Opthalmologists, Optometrists, and other “experts” still seem to cling to the old 20/60 rule. My vision acuity has always been correctable to at least 20/30. The fact that I often see two images that compete with each other seemed to mean nothing most of my life. The fact that I can mesh the two images into into blurry letters that are distinguishable on the Snellen eye chart’s 20/20 or 20/30 row was all that mattered. It was immaterial that my 20/30 vision was too difficult to hold together for more than a minute, or two at best.

But, thankfully, an increasing number of vision care specialists are now recognizing a more accurate view of Vision Impairment. Interestingly, this broader view has also validated the dictionary! So once again, I offer my simple definion of Vision Impairment:

Vision Impairment is a state in which the act or power of sensing with the eyes (sight) is worse than optimal; diminished in ability, value, or excellence, etc.; weakened or damaged.

Vision impairment can come in many forms, some mild, and some severe. Regardless of how it comes, it is valid, and deserves to be recognized and offered the best treatment and opportunity available for each of it’s various forms.

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