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I am doing my science fair project on depth perception. Can you tell me a good, easy way to test for this?

Billy Reimsnider
10 years old

Hi Billy,

I have a great site for you to look at. My friends at the Optometrists Network have created a website that has exactly what you are looking for. The directions are there with pictures explaining what to do to test for depth perception. Please visit them at http://www.vision3d.com/frame.html.

Have fun with your science fair project!

Your pals,
Twinkle & Eyenstein

TWINKLE AND ENSTIEN MY FAMILY AND I ARE IN A BIG ARGUMENT ABOUT EYESS I SAY THAT THERE IS AN EYE COLOR GREY THEY SEEM TO THINK DIFFERENT. SO MY QUESTION IS IS THERE AN EYE COLOR GREY. IVE TRIED TO LOOK IT UP IN THE ENCYCLOPEDIA IT DIDNT SAY ANYTHING I TRIED ASKING ASK JEEVES AND HE DIDNT SAY ANYTHING ABOUT IT.SO PLEASE TRY TO FIND MY ANSWER.

THANK YOU VERY MUCH
mary fox

Hi Mary,

Thanks for writing with your question about gray eyes. The answer to the question is this: gray is NOT an eye color. Sorry, but your parents were right (they usually are!).

Here's an explanation:

The color of your eye is determined by a pigment called melanin. Melanin allows for only 3 colors of eyes...brown, blue, & hazel. The brightness of the eye color is determined by how much melanin there is in the eyes.

Sometimes people can appear to have gray eyes, but their eyes' pigmentation is not actually gray. In actuality, their eyes could be blue, brown, or green, but there is so little pigment that the light reflecting into the eye gives the illusion that the eyes are of a grayish color. This is especially prevalent in albino people, who have very little pigment in their eyes and skin.

Thanks for writing!

Your pals,
Twinkle & Eyenstein

Dear Twinkle and Eyenstein,

My second grade class would like to know, what is the most common color of the iris in people? We also would like to know what is the color of the retina in humans?

Thank you,
Cherlyn

Dear Cherlyn and class,

What good questions! Your first question, about the most common color of the iris, is a question that isn't easy to answer.

The color of your iris comes from something called "pigment." Pigment is what makes your body so colorful! A type of pigment called melanin is responsible for coloring your eyes and your skin.

Let's talk about the pigment in your iris. The more pigment there is in your iris, the darker your eyes will be. So brown-eyed people have more pigment in their irises, and blue-eyed people have less.

Guess what determines whether you have a little pigment or a lot! The answer is -- your mom and dad! Every one of the cells in your body is made up of genes that you inherit from your parents.

Here's where it gets a little tricky!

You have 2 eye-color genes -- one from each parent. How their genes match up determines your eye color. If you get a brown gene from one parent and a brown gene from the other parent you will have brown eyes. If you get one brown gene and one blue gene, you still have brown eyes. You will only have blue eyes if you get a blue gene from both your mom and your dad. This happens because brown is "dominant". That means that it is the boss and so it gets to be first. Blue is "recessive". It can only be the boss if there are two blues together.

(Green eyes are even more complicated. They have another pigment or color called lipochrome. Some people have little or no pigment at all! Their eyes look pink because you see some of the color from inside the eye.)

The pigment in the iris helps keep harmful sunlight from hurting the inside of the eye. People living near the equator, where its sunny for most of the year, usually have darker eyes. People living far north or south of the equator, where there is less sunlight, usually have lighter colored eyes. But nobody really knows for sure which is the most common color. It would be too hard to count everybody around the world. If we had to guess, we would say brown. What do you think it would be? Do a poll in your class or even in your school, and let us know what you find out!

Whoops! We almost forgot your other question. You wanted to know what color the human retina is.

The answer is: the retina looks red, but its actually clear...no color at all!

Your retina is made up of many different layers. These thin, clear layers might remind you of plastic wrap that you use in the kitchen to wrap up leftover food. But your retina looks red or orange because of the blood vessels that are in another layer, called the choroid, which is underneath the clear tissue.

Thank you for asking questions. We love getting email! And your questions were so good that we've posted your question and our answer on our website in the "Ask Twinkle & Eyenstein" section.

Bye for now!

Your pals,
Twinkle & Eyenstein

Dear Twinkle and Eyenstein:

I am in grade four. I am doing a science project on the human eye. I would like to build a model of the eye but I don't know how. Do you have any ideas?

I learned a lot about the eye on your sight. it is great!

Mathieu Comeau

Twinkle & Eyenstein respond!

Hi Mathieu,

So, you're going to make a model of the human eye? Here are 2 of our ideas...

#1. Papier-Mache! Sure, it can be messy and a little smelly. But then sometimes that's what makes a good science project, right?