The human eye is an energy converter. It has the ability to convert light energy into chemical energy which is transmitted from the eye to the brain via nerves. The eye’s color receptors are called cones simply because they are shaped like cones and the night vision receptors are calledrods because they look like little rods. There are three different types of cones. They are blue, red and green receptors and from the combination of these three types of receptors we can see approximately 10 million different colors. Humans have an abundance of cones in the center of their vision and this gives us the ability to see color better in the center and less towards the periphery. Some animals can see better at night because they have more rods than cones but give up the ability to see colors as well as we do.
The rainbow is composed of millions of colors but these are grouped into seven general categories. Red, orange, yellow, green, blue, indigo and violet, ROYGBIV. Within each of these categories are millions of shades of these colors or hues. Certain health conditions and medicines can impair one’s ability to see colors. Cataracts are when the internal lens of the eye becomes yellow or cloudy white, this absorbs the blues and the person sees things more yellow and red. Some of the medicines that decrease color vision are: Viagra, yes that’s correct, it can give things a bluish tinge for several hours after taking the medicine; Plaquenil is a drug that is used to treat malaria and some forms of arthritis; Coradone is used treat cardiac arrythmias; among others. Frequent eye exams are recommended for those on these meds.