What is blindness?

Blindness is the condition of lacking visual perception. Various scales have been developed to describe the extent of vision loss and define blindness. Total blindness is the complete lack of form and visual light perception and is clinically recorded as NLP, an abbreviation for "no light perception." Blindness is frequently used to describe severe visual impairment with residual vision. Those described as having only light perception have no more sight than the ability to tell light from dark and the general direction of a light source. In order to determine which people may need special assistance because of their visual disabilities, various governmental jurisdictions have formulated more complex definitions referred to as legal blindness. 

In North America and most of Europe, legal blindness is defined as visual acuity (vision) of 20/200 (6/60) or less in the better eye with best correction possible. This means that a legally blind individual would have to stand 20 feet (6.1 m) from an object to see it—with corrective lenses-with the same degree of clarity as a normally sighted person could from 200 feet (61 m). In many areas, people with average acuity who nonetheless have a visual field of less than 20 degrees (the norm being 180 degrees) are also classified as being legally blind. Approximately ten percent of those deemed legally blind, by any measure, have no vision. The rest have some vision, from light perception alone to relatively good acuity. Low vision is sometimes used to describe visual acuities from 20/70 to 20/200.

Color Blindness

Colour Blindness is sometimes characterized as a disability, color blindness can be caused by a number of things such as nerve damage, genetics, and in some cases, exposure to certain types of chemicals. The most common type of color blindness is individuals not being able to distinguish between red and green colors. Having this disability can cause problems in ones daily activities. For instance, driving can be an issue, when stopping at traffic light and waiting on the red and green lights. The simple task of cooking can become an issue as well, not being able to know if any types of meat you are cooking is completely done.

Night Blindness

Also known as Nyctalopia, is when someone has difficulty seeing in dim light. This type of blindness can be caused by the lack of vitamin A or the retinitis pigmentosa, which is where the rod cells in the retina begin to loose the ability to respond to light. Also, night blindness can be caused by an injury or it can be present at birth. 

What is Braille?

Braille is a system of reading and writing that uses embossed dots. Braille characters are formed by using different combinations of six dots. These dots are arranged in a pattern called a Braille cell which is two dots across and three dots down. Louis Braille, who was French, invented this system of dots in 1824 when he was just 15 years old.

Touch and your fingertips

The hand is the organ devoted to touch. Touch can be sensed all over the body, but the real tact is concentrated in the hand and fingers, which move over an object to determine its volume, temperature, and nature. The fingers of man have epidermal and dermal folds, which we call the fingerprint. These fingerprints are unique to each individual, and allow an increase in the surface area of the skin at the ends of the fingers greatly raising the number of sensory receptors present. The hand is also an organ, which allows us to communicate. Deaf-mutes employ a sign language using their hands the blind read Braille with their fingertips.

The visually impaired reader moves his fingers over the paper, detecting the points standing out in relief, and associates a combination of points with a letter then a word. The blind are capable of reading 150 words per minute (300 to 1,000 words per minute for sighted person).
The threshold of sensitivity of the skin corresponds exactly to the dimensions of a Braille character. The sensitivity of an organ is defined by the sensitivity threshold to a mechanical stimulation (entry of a point to a depth of 6 µm) and the spatial discrimination threshold (separation measured with dividers). Lowest thresholds occur at the tip of the tongue and on the fingertips (1-3 mm). The fingers have a very high density of touch receptors, which has led to an over-representation of the fingers in the somato-sensory cortex. The threshold of sensitivity of the skin corresponds exactly to the dimensions of a Braille character. The detection of Braille characters depends entirely on Merkel cells and Meissner corpuscles. Merkel cells, which are stimulated by angles, points and curves, provide the spatial characteristics of the Braille symbols, while Meissner corpuscles supply the temporal information. Because of the discrimination threshold, a Braille character is 4 mm x 6 mm, thus an A4 Braille page (21 X 29.7) only contains 27 lines of 30 Braille characters. A Braille book thus occupies 3 to 6 times more volume than the same document in normal script. 

Blind dining a culinary experience

Blindfolds and braille aren't things you may normally associate with dining out but a culinary event with a twist is part of this year's New Zealand International Science Festival – and organisers hope guests will leave with more than just a satisfied hunger. Guests are blindfolded, the menus are in brail, as science festival organisers hope to tempt the tastebuds and stimulate the senses. Julie Biusos created the dining in the dark menu and says presentation is usually a key ingredient in her job but with blindfolded diners there are other things to consider.

"It's quite a challenge to think beyond that square; of course I've had to make sure no accidents nothings going to end up in the lap," Ms Biuso says.

And to dine, blind isn’t just a challenge for the menu designer. If they are finding the whole thing a bit hard to swallow it's a daily experience for chef Julie Woods who has been visually impaired to for 13 years. Not that it has slowed her down in the kitchen; instead Julie Wood now relies heavily on touch.

"I can tell when chickens cooked because the skin gets touch of you can identify where objects are in the kitchen by their shape of by what's left on the bench so there's a lot of information that you use by your sense of touch," Ms Woods says.

Ms Biuso hope to give diners more that just fine food to chew on.

"We do take things for granted and so it'll make them a little more understanding of people who can't see."

A sense blind diners may appreciate a little more.

References:

http://en.wikipedia.org/wiki/Blindness

http://www.associatedcontent.com/article/2797678/different_types_of_blindness.html?cat=5

http://www.rnzfb.ord.nz/learn/accessible-information/braille

http://www.skin-science.com