Vision Therapy

Color Vision

Have you ever wondered how animals see?  We have all heard stories since we were little about how cats can see in the dark and if you are a hunter that deer can’t see certain colors whereas turkeys can.  What accounts for these differences?  It all comes down to rods and cones.

color wheelEssentially rods and cones are the light and color receptors in our eyes respectively.  What makes the differences across various animals is the number and ratio of each.  Rods and cones get their names because of their shape — you guessed it; rods look like rods and cones look like cones.  Rods are primarily sensitive to light and cones are sensitive to colors. 

Since this post is about color vision I will only be talking about cones.  Humans normally are what are called trichromats.  That means that we have three cones on our retina that are most sensitive to color – red, green, and blue.  This is actually an oversimplification.  In reality it comes down to the size of the wavelengths and not the actual colors but that is for an optometry textbook and not a blog post.

black and white dog

People with color blindness are not using one of their cones — usually the one related to the color red which is why red and green more or less look the same.  This is also the case with dogs.  That bright red and yellow fire hydrant toy actually looks like a dark brownish gray to Fido.

Deer are also dichromats which explains why so many deer hunters wear blaze orange without a problem.  Deer cannot see orange so a hunter wearing that color blends into the background like a gray outline.  Wearing head to toe blaze orange though isn’t a good idea because a deer can pick out your shape pretty easily having been wired with a brain that is locked into prey mentality.

Most birds such as turkeys on the other hand have full color vision and have very good eye sight so full camouflage even to the point of what is called a leafy suit is necessary for hunting them.

Just like there are color blind people that are essentially dichromats, there also are people that are tetrachromats.  Only women have this possibility – again this is just a blog post and not a lecture about genetics.  They have the possibility of seeing 100 million colors as opposed to our lowly 1 million colors.  Don’t feel too bad though, in questioning a woman who is a full – tetrachromat (has four cones and is aware of more colors) it seems to point out that she only notices more variability in color and not really any more colors per se.  But how do you explain the color red to someone who is color blind?


Read more about a woman who is a tetrachromat:

“Scientists find woman who sees 99 million more colors than others”