|Inside: a pupil dilation experiment you can do at home with kids. It’s a hands-on way to discover how quickly our eyes adjust to a variety of light conditions.|
Do your kids have an eye exam coming up? Is it going to involve pupil dilation to examine the back of the eye?
We recently took our 9-year-old for just such an exam, and it was a very traumatic experience for all involved. To prep for the day, we read the Eye book by David Macaulay and explained to our son that as part of the exam, the ophthalmologist will place eye drops in each eye to widen the pupil. That will allow more light in so the doctor can see inside the eye.
My son, who is usually very reasonable and easygoing, absolutely refused to have the doctor place drops in his second eye because (according to him) his first eye was burned by the drops.
We bribed. And yes, we threatened. (And believe me, this approach goes against all my parenting principles. But the doctor thought that my son really needed the exam because I had holes in my retina at a young age, and it’s hereditary). The doctor was getting very annoyed, which was making the situation even worse (we have since changed the doctor :). The waiting room area was getting very noisy as we were holding up the traffic. But my son just got stuck in the “no way I’m doing this” mode.
You’re probably wondering why didn’t we just leave, let him snap out of it, and return on another day. It’s hard to believe, but pediatric ophthalmologists in Chicago are booked a year in advance. If we had walked out of that appointment, we would have had to wait another year to return.
When the doctor refused to wait any longer, we used force. So, a receptionist, a nurse, and my husband held down my 9-year-old while the doctor advanced with the eye drops at the ready. In the ensuing scuffle, the drops made their way on every surface in the room. I’m surprised we all didn’t walk out of there with dilated pupils. It was a battle of epic proportions.
When it was over, we were all mighty relieved. And the inside of my son’s eyes was just fine, thanks for asking.
As soon as he was calm, we talked about the experience and further connected by reading aloud a Star War book that my son likes. When he went to play with his siblings, I started planning an Eye Dilution experiment in my head. Since we fear things that don’t make sense to us, I believe the more that we know and understand, the less we fear.
Whether you have an eye exam coming up or not, you might enjoy trying this pupil dilation experiment with your kids.
>>> We have science printables that go along with this experiment. Click the image or enter your email here for the download.
Pupil Dilation Experiment
Let’s have a look at the pupil with a doctor’s eye.
Supplies for Pupil Dilation
- Magnifying glass
- Handheld mirror
- Flashlight (we used a phone flashlight)
What to do:
- The parent places the magnifying glass on the mirror and holds it up for the kid (with the magnifying glass facing the child). Ask your kid to look into the center of the magnifying glass. He/she might need to move his/her head around to get a good image of one eye at a time. Older kids can hold the mirror and magnifying glass on their own.
Ask kids to look at
- the white of the eye,
- the colored part of the eye, or iris,
- the black hole in the middle of the iris, the pupil.
- Hold a flashlight with your other hand, place it behind the mirror, and shine the light around the edge of the mirror into your child’s eye.
Can you see your pupil change size?
- Go to a dimly lit room (bathroom, perhaps) and repeat step 1. If you don’t have a night light, use a candle or a flashlight that is turned away from you, so it’s not too bright.
Did you notice that it takes longer for the pupil to dilate than to contract?
Repeat the same with the other eye.
Here are some of the questions that came up during our experiment.
How do we see things?
The pupil is a hole in the center of the iris, the colored part of the eye. Through this hole, the light travels to the back of the eye. The light is then coded into a nerve signal that travels to the brain. Your brain decodes the message and interprets it.
What does pupil size have to do with it?
The iris regulates how much light gets into the eye. Pupils are smaller in bright light and larger in low light. Your pupils also expand when you are nervous (if you see a bear) and when your brain is working on a very hard math problem (the harder the problem, the bigger the pupil).
Why the drops?
To see well inside your eye, your eye doctor needs to use a very bright light. This bright light causes the pupils to constrict. A doctor uses medicated eye drops to immobilize this light reflex. The pupils stay wide open even when a doctor is shining a bright light into the eyes to illuminate the back of the eye.
Can a flashlight hurt my eyes?
According to the American Academy of Ophthalmology, a typical flashlight cannot hurt your eyes. Iris, retina, pupil, and optic nerve all work together to activate our built in defense ability to protect our eyes from the glare of bright light. The first impulse is to blink (to shut the eyes from the glare), and by the time the blink is over, the pupils are constricted. But don’t go around doing it for fun!
Books that helped our Eye investigation
The Eye Book by Dr. Seuss
Eye to Eye: How Animals See the World by Steve Jenkins
Where Did You Get The Color of Your Eyes by Baby Professor
How Can My Eyes See? Biology 1st Grady by Baby Professor
The Doctor with an Eye for Eyes: The Story of Dr. Patricia Bath by Julia Finley Mosca
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All my kids ended up participating in this experiment, and we had a lot of fun! I personally never looked at my eyes with a magnifying glass before, and I found the whole experience fascinating. I was as excited as kids to run between the flashlight and the dark room. It was a truly hands-on way to discover how quickly our eyes adjust to a variety of light conditions.
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