Color Deficiency is frequently referred to as "color blindness". In reality, rarely is anyone ever totally color blind. In most cases there are only varied reductions in the individuals color perception. Each individual is totally different. Color deficiency occurs when one is not able to distinguish the differences between certain shades of color. The cause of color deficiency is often inherited, but can be the result of disease, medications, or trauma. In the color deficient eye, the cone cells, which are found in the retina on the back of the eye, are not transmitting the color message to the brain correctly.
The human eye is sensitive to wavelengths in the electromagnetic (EM) frequency spectrum from 400 nm to 700nm. The central 30 degree part of the back of the eye, predominently contains the "CONES", which are the color nerve ending receptors. There are three different types of cones which are sensitive to three different ranges of wave lengths:
The "Blue" cones pick up wavelengths from 400nm to 540nm.
The "Green" cones pick up on 500nm to 630nm. "Red" cones pick up wavelengths from 500nm to 690nm. Below 400nm is classified as "Ultra-violet", while above 700nm is classified as "Infra-red". Both of those regions of the EM spectrum are invisible to the human eye without special electronic devices. (see: Ultraviolet Protection (UV), and Night Scopes, for more information about dealing with these issues.)
EFFECTS FROM COLOR DEFICIENCY
For many individuals, a mild color deficiency may have very little significance on their life. They may find that selection of wallpaper or the right dress or tie in the morning to be a minor a slight inconvenience. It is, however, of value for the individual to know what the status of their color vision is so that they can take that into account in the normal transactions of their daily life. For others, it may be very important. The selection of ones occupation or even their elegability to a field of work may be limited, if a color deficiency is present. For example, a young person contemplating a carrier as a "miltary pilot" would find it difficult or impossible to reach that goal, since many items in aviation are classified by their color. Examples of color classifications include: electronic wiring, smoke flares and aviation fuel. Another example would be someone who is interested in the field of painting. While a color deficiency might not prevent this field of work, it would certainly be important for the individual to be aware of the exact wavelengths (color) that they are deficient in.
CLASSIFICATION OF COLOR DEFICIENCY:
-- PROTANOMALY: Reduced sensitivity to RED colors
-- DEUTANOMALY: Reduced sensitivity to GREEN colors
-- TRITANOMALY: Reduced sensitivity to BLUE / YELLOW
-- PROTANOPIA: Total loss to RED colors
-- DEUTANOPIA: Total loss to GREEN colors
-- TRITANOPIA: Total loss to BLUE / YELLOW colors
COLOR VISION TESTING
There are many different types of color vision testing equipment. The following are commonly used tests:
-- PSEUDO-ISOCHROMATIC PLATES (Ishahira)
These are a series of plates which have a matrix of dots
arranged to show a number. To those who have normal
color vision, the number is easy to see. For those who
do not have normal color vision, the numbers blend into
background of dots and therefore the number may not be
able to be identified.
-- FARNSWORTH MUNSELL TEST
This test is more clinically useful due to a
somewhat more quantitative evaluation of the color
deficiency. In this test there is a tray of colored caps.
They are presented in random order. The individual is
instructed to arrange the caps in chromatic order
between the two reference caps at each end of the 4 trays.
The misalignment of these colored caps from their correct
position in the series is then scored. The greater the
displacement the higher the score.