What is Visual Impairment?
As reported in The Encyclopedia of Blindness and Visual Impairment, The World Health Organization estimates that there are between 40 million and 45 million blind people in the world, and an additional 120 million suffering from disabling low vision… [and] the number of people who are blind or visually impaired will double by the year 2025
(Sardegna).
Have you ever reflected on how important eyesight is? If you wear glasses of contact-lenses, you may realize that perfect eyesight (or at least being able to read comfortably), is crucial to everyday activity. Those falling under the classification of “visually impaired” are still able to interact with the world every day, but must take in visual information from a different approach.
Types of Visual Impairments
There are multiple types of visual impairment. A few of the common ones are Amblyopia, Retina Pigmentosa, and Retinopathy of Prematurity. Amblyopia is a common eye disorder that is often nicknamed “lazy eye.” One with this condition has weaker eye muscles and the eye with the condition has poor positioning. Although there is surgery to treat this, an effective solution is to try and strengthen the affected eye by placing an eye patch over the other one. By doing so, the lazy eye has to work harder and its muscles can strengthen. Retinitis Pigmentosa is another condition in which a person suffers from a degenerative loss of their peripheral vision. Retinopathy of Prematurity is another common type which involves premature babies. Babies that are born into the world need higher oxygen levels and the eyes scar and detach from parts of the retina at birth.
Approximately 14 million people in the United States are visually impaired to some degree. 3 million of that number have conditions in which their visual impairment conditions cannot be corrected by glasses or contact lenses. The diagram below visually shows the statistics.
The following are tests that a doctor can prescribe, as quoted by TeensHealth:
- Visual Acuity Test – A person reads an eye chart to measure how well he or she sees at various distances.
- Visual Field Test – Ophthalmologists use this test to measure side, or peripheral, vision.
- Tonometry Test – This test determines the fluid pressure inside the eye to evaluate for glaucoma.
Complete Blindness
Complete or Total blindness has been to defined to be a complete loss of light perception (NLP). Individuals who are completely blind are unable to distinguish any changes in light or any movement in front of them (Sardegna). Complete blindness is the most severe out of all the cases and the difficulties met by those individuals is much greater than those who suffer a more minor case of visual impairment. The aid that totally blind people can receive is limited because of their inability to sense changes in light which restricts only uses aid that interacts with their other senses.
Partial Blindness
Most people with any visual impairment fall into the category of having Low visions which consists of several different types of visual impairment. Many of these individuals fall into a category with terms including medically blind, legally blind, partially blind, partially seeing, low vision, functionally blind, braille blind, vocationally blind, economically blind, visually defective, visually impaired, visually handicapped and visually disabled
(Sardegna). Legal blindness is a term used by federal entitlement agencies to determine whether or not an individual qualifies for benefits. One may be classified as legally blind if their visual acuity (area of vision) is less than 20/200 in the better of both eyes with correction or if visual field, even with 20/20 vision, is limited to 20 degrees or less.
Color Blindness
Eyes interpret color through the retina which converts light energy into electric energy that is sent to the brain to be translated into an image. Photoreceptor cells in the retina contain three rods which interpret the three simplest light wavelengths; red, green, and blue. Color blindness occur when one rod is unable to interpret its wavelength correctly. There are many different types of color blindness which limits what colors individuals have trouble seeing. Most individuals who are color blind see some colors but lack the ability to see others; for example, some may see every color but red or green which they see as grey or black (Sardegna).
Colorblindness exists to varying degrees, and is sometimes undiagnosed until adulthood. To test if an an individual is colorblind (and to what degree), doctors present a series of plates with numeral-shapes hidden among circles of many sizes and colors. The specific numerals a person sees (or doesn’t see) can give doctors a complete and accurate idea of the person’s vision.
