Color vision deficiency (CVD) or color blindness is the inability or decrease ability to distinguish different colors under normal lighting conditions. Human color vision is normally trichromatic i.e the mixture of red, green and blue lights. There is no actual color blindness because there is only a fault in the development of one or more sets of retinal cones that perceive color in light and transmit that information to optic nerve.
CVD is one of the commonest disorders of vision. Color vision is integral to an individual ‘s understanding of their visual world and those with CVD can experience difficulties in everyday life. However most of colorblind cases remain undetected due to the absence of proper screening.
Type : CVD maybe congenital or acquired.
Congenital color defect are non – pathologic incurable and constant throughout the life. It is genetically determined by X- linked recessive inheritance. Its incidence varies race to race and different in different geographical area of the world inhabited by people of different ethnicity. Impaired color vision are mostly red – green color blindness. Up to 8 % of the world male population exhibits type of CVD and 0.5% of females are affected by CVD. Thus congenital CVD occurs more in male but is transmitted via female and about 8 % of all women are its carrier.
| Classification of CVD | Description |
|---|---|
| Protanomaly | Red weakness |
| Deuteranomaly | Green weakness |
| Tritanomaly | Blue weakness |
| Protanopia | Red deficiency |
| Deuteranopia | Green deficiency |
| Tritanopia | Blue deficiency |
Acquired color blindness develop later in life and can affect men and women equally. There are some acquired causes for colorblindness such as damage to the eyes, nerves brain, some metabolic disorders like diabetes, glaucoma, macular degeneration, chronic illness like – sickle cell anemia; even exposure to industrial toxin or drug over dose such as digoxin, barbiturate’s, anti – tubercular drugs or drugs side effects like sildenafil, ethambutol chloroquine.
Color vision deficiency does not cause complete blindness. It is alternation of the three (Red, Green and Blue) cone pigment are responsible for color vision deficiencies. A mild color deficiency is present when one or more of the three cone function poorly. There are very few cases whose color deficiency exists to an extent that no colors can be detected. They can only see black, white, gray.
There are many occupations where normal color vision is requirement. Armed forces, railways, merchant shipping, navigation , civil aviation , police and fire service , electrical contracting , some other types of electrical engineering , medical field , hospital technicians, pharmacist , sports, pilot etc.in these field normal color vision is required. Therefore, detection of color blindness at an early age can be extremely useful to avert or prevent certain occupational hazards including death in case of drivers of locomotives and automobiles. Person with color vision deficiency can experience difficulties in everyday life but develop adaptive strategies and behaviors which help them to deal with any potential difficulties they face in their professional and personal lives. Therefore, they never complain about color vision.
Congenital color blindness cannot be treated since this type of color defect are non- pathological and remain constant throughout life. Although several therapies have been proposed (e.g. electrical eye stimulation, iodine injections, large doses of vitamins), there are no treatments or surgical procedure to improve the quality of an individual chromatic vision. Optometrists give colored spectacle lenses or a single red tint X-chrom lens to be worn over the non -dominant eye. Although this may improve discrimination of some colors, it can make other colors more difficult to distinguish. That contact lens may allow the wearer to achieve a better score on certain color vision tests, it didn’t correct color vision in the natural environment . Many application for iphone and ipad have been developed to help color blind people to view the colors in the better way. Many apps launch a sort of simulation of color blind vision to make normal to view.
There is high proportion of school children are unaware of their color vision status and un-diagnosed CVD which mislead them in future for their career selection .Therefore , the government must take initiative for color blind awareness among the different population in the state to guide the color blind individuals towards right path and increase awareness of the needs of colorblind people in everyday life. In this condition , school children with CVD must be given career advice which includes information as to which careers they may find to be difficult or impossible to follow and also help school children preventing them from struggling in the classroom due to lack of awareness of the possible effects of their disability by both their parents and teachers. Teachers training should be given how to treat color blind children in school environment. Moral support from the family and society is required for the healthy development of mental status of the individual suffering from this disorder.
Now, while doing school screening we can add color vision test also and for pediatric patients who came to hospital / clinic color vision test can be included in comprehensive examination. This help detection of color blindness at an early age which make their parents and them aware about choice of career.
Author Sarita Gupta Optometrist, Orbis REACH Project R.M Kedia Eye Hospital Parwanipur,Bara