The Multiple Definitions of Blindness

Recently a visitor found Blind Not Alone while searching if “light perception only” might be considered blindness. If not blind myself, I can understand the confusion one encounters trying to define this as a concept. After all, Blindness possesses medical, legal, social, and other definitions. For example, the Merriam-Webster Medical Dictionary lists the following definitions:

  • Lacking or deficient in sight
  • Made or done without sight of certain objects, facts, or knowledge
  • Having no knowledge of a certain aspect of research

On the surface, these definitions appear rather neutral, but lack any actual substance. The first definition comes the closest to answering the question about the level of sight one needs to be considered blind. The other definitions touches upon blindness in some social constructs. Exploring medical and social definitions of blindness, this post will merge together several beliefs of blindness. Being quite critical of blindness, I hope to engage your emotional beliefs about blindness, demonstrating other methods one views to abuses the word blind.

Medical Definitions of Blindness

Medically, blindness defines a severe or limiting visual condition caused by an array of diseases and conditions arising from genetic predisposition, traumatic injuries, environmental exposures, secondary to other diseases and a host of other causes. Eye care specialists and rehab therapists obtain the severity through optometric evaluations and functional tests. In this setting, the International Classification of Diseases 10 (ICD-10), identifies several categories related to sight. Please note that the term functioning is used and not disorder or disability, since none of these should be considered as abnormal or negatively, but just part of life.

  • normal Vision refers to a person with correctable acuity of 20/20 in best eye, and visual fields that exceed 40%.
  • Visually Impaired includes all of the below categories for sight loss where correctable acuity or fields in the better eye cannot obtain normal sight parameters.
    • Low Vision consists only of moderate and severe visual impairments, and not blindness. Low vision acts as a catch all for those who have a significant amount of usable sight, but not enough to partake in the privileges afforded to normal sight levels, like driving.
      • Moderate Visual Impairment refers to a correctible visual acuity between 20/70 and 20/160 in better eye.
      • Severe Visual Impairment is a visual acuity between 20/200 and 20/400 in best eye corrected.
      • Profound Visual Impairment refers to individuals with a corrected visual acuity in best eye between 20/500 and 20/1000 or 5/200.
    • Blindness is not a precise catchment, but for simplicity includes two sub categories.
      • Near Total Blindness refers to a correctible vision in best eye 20/1000 or 5/200 in best eye or worse, i.e. can see fingers, motion, or light perception only.
      • Total blindness is the absence of any ability to perceive any form of light or visual stimuli through the eyes.

This information comes from the American Optometric Association (AOA) and the World Health Organization.

If you are confused by the categories, you are not alone. Attempts to classify visual impairments is as much a subjective stance as much as it derives from empirical research. Efforts and research has been published to alter these definitions as noted in the articles from the World Health Organization and this NCBI article calling the classification of visual impairments outdated. Both of these articles possess solid support, given the system originated in 1972 from a World Health Organization special interest group. Secondly, relying on visual acuity fails to account for how functional the remaining sight is, which is subjective information from the person rather than an objective measurement. Finally, we have the individual who struggled to determine themselves if “light perception only” is a form of blindness.

I am not going to begin the process to dissect the International Classification of Diseases 10th edition’s codes related to sight. If you are interested, feel free to search for ICD-10 H53 and H54 in Google or Google Scholar. h53 refers to functional visual deficits, like blind spots, night blindness, functional visual impairments, and similar. H54 gravitates towards defining different forms of blindness and causes. I will cover Legal Blindness while reviewing social definitions, since it delineates cutoffs for various programs rather then illustrating medical necessity. The outdated notion of legal blindness in ICD 10 is H54.8, though ICD-9 referred to this as 369.4.

Defining Blindness Socially

Despite the concrete medical definitions of blindness, our daily usage of the terms varies significantly. Take a few minutes and reflect how blindness surfaces in regular conversations, favorite media outlets, religious scriptures, and personal beliefs. How many times do you use or hear the word blind issued forth as:

  • To define a person using a white cane or guide dog?
  • Offensive term yelled while driving when you are cut off?
  • A research method whereby an aspect of the study is unknown to the participant and/or researcher?
  • During sporting activities?
  • Disapproving of one’s selection of clothes or referring to one with mismatched color schemes?
  • Used against a person spouting political or religious rhetoric in opposition to your own?

These are just some of the few examples we might think about or utter the word blind. Some carry neutral tones like stating a fact, while others aim to belittle or create a sense of fear. Very few times might blind be used in a positive fashion. Overall, its these non-medical aspects of blind we encounter daily. Though this next section will examine a couple of mainstream ways we use blind, its up to you to continue to assess your thoughts.

Starting off, blind spot or blindside surfaces in numerous situations from the previously discussed medical situations to an area blocked or residing outside one’s field of view. As a NFL Chicago Bears fanatic, its not uncommon to hear references referring to the Quarterbacks blindside, generally alluding to the left side of the offensive line for right handed throwers, like whenever Jay Cutler is pressured out of the pocket or sacked. Blind spot also means an area where a driver cannot directly see without completely turning their bodies or usage of a mirror or sensor. Fortunately, blindside and blind spots are fairly neutral in their regular usage. In the world of research, a blind or double blind study describes a method whereby a researcher or participant does not know which sample population is receiving a placebo. This results in an increase to validity of the study, and one of the few situations where a sighted individual gladly extends themselves just to mention they were blind.

Though mentioned above, legal blindness should be viewed as a social construct, thanks to the cutoffs erected by Governmental agencies, legal systems, and organizations basing services, entitlements, and benefits around it. Denoting very little in medical terms, legal blindness arose from the 1930’s in the New Deal, and since dispersed throughout society. However, a more severe legal precedence instilling fear in many stems from how blindness relates to driving privileges. When linking sign loss with driving, think about what images immediately surface. Any chance they might consist of elderly drivers or belligerent people accusing others of blindness? Interestingly enough, many individuals favorably view legal blindness and how it opens different doors favorably, while the lesser loss of sight forcing one to lose driving privileges is met with much fear, concern, depression, and numerous other emotions.

Placing religious and political together might seem absurd, but both belief systems feature blindness similarly. Outside of the various parables and stories where a blind person is cured, blind often describes a person rooted in a particular ideology. In this Huffington Post article, a cleric accurately compares the blind faith we might bestow upon a sport team, but notes the tragic loss we all face when placing the same blind trust in political views. Similarly, blindness appears in scriptures as this quote from 1 Corinthians 2:14 depicts, “Those that are not rightly instructed in the true knowledge of God, are as blind in matters of religion as the blind man in seeing what is before him in the way (. “This passage uses blindness to define the lost of vision and connects it to a loss of faith, leaving a rather negative connotation for the blind. Regardless, blindness describing a myopic and concrete set of values, ideologies, and beliefs elicits a very charged response.


After seeing the different methods, we use the term blindness, its very easy to understand why the term might confuse, enrage, or positively define one. Personally, I switch between visually impaired and blind, when discussing my sight based on the audience, but neither engages me emotionally. Instead of trying to determine if someone is blind, one should simply accept the different methods our brains interpret visual input. If you absolutely must inquire about one’s sight outside the confines of a medical situation, try to ask questions about personal meaning or how one accomplishes different tasks. You will learn far more about the individual this way, than asking what constitutes blindness.