Pioneer students get hands-on lessons on eyes
August 27, 2008 · Updated 4:34 PM
ARLINGTON Pioneer Elementary fourth-graders received a hands-on education in human anatomy, through a Marysville doctor with a bag of cow parts.
Dr. Kim Kron, of Marysville Vision Source, and his staff visited Paula Barnard and Suzie Chandlers fourth-grade classes Feb. 7 to teach them about how human eyes work, and to do that they brought cow eyes for dissection.
Weve been studying the bodys systems and grouping them by subject matter, Chandler said. We love to get kids parents and grandparents involved and Sherry Vernal, one of the assistants here, is the grandmother of Joel Williamson, one of our students.
Chandler and Barnards students had already studied the eye through textbooks, but through Vernal, they were able to bring in Kron and his staffs program, which has already proven popular among Marysville students.
Kron began the lesson with a side chart of the human eye, summarizing its parts as similar to those of a camera, with the iris opening and closing to filter the amount of light received by the lens onto the retina, which he described as the film in the camera of the eye.
From there, its sent to your brain by the optic nerve, which is like the cable of your computer screen, Kron said. Those nerves meet and cross over in the middle of the brain, so that the upside-down images on the back of your eyes are turned right-side up.
Even before Kron and his staff moved on to showing the parts of the eye, by cutting open the cow eyes at each table, the students deluged him with dozens of questions, many inspired by their own experiences.
Why can I see to the side, only not as well? one student asked.
Your best vision is going to be at the center of your eye, where the image is strongest on the retina, Kron said. Your peripheral vision wont be as sharp, but it gives you a sense of location and warning.
When I press on my eyes, I see spots, another student said.
In the vitreous fluid sac inside of your eye you have blood, Kron said. When you put pressure on it, you cause the gel and blood to reform. The older you get, the more you can see the little strings and dots of gel that are floating around inside your eyes, especially against a blue sky.
Kron explained that iris colors dont affect vision and are determined by the same inherited genetics as other physical traits, before clarifying what color-blindness actually means.
Its rare to be truly color-blind, Kron said. Most people who are color-blind are actually color-deficient. its not that they see in black and white, but rather, they dont see red and green in the same way as the rest of us. Sometimes, its that they dont see blue and yellow in the same way. Either way, its much more common in boys than girls, even though girls pass it on.
When one student wondered why she saw things in the dark that werent there, Kron compared it to what happens when other limbs are positioned in ways that disrupt their regular blood flow.
When you lay down for a long time, blood begins to settle in the back of the eyes, Kron said. Its like when your foot is asleep and, after a while, it starts to tingle.
Why do your pupils get big when you see someone you love? a student asked.
Blood supply is affected by hormones and chemicals, Kron said. When youre excited, your pupils will dilate.
Kron noted that people also blink less often when theyre mentally focused, before emphasizing the importance of safeguarding ones eyes from the sun.
The reason youre not supposed to stare at a solar eclipse is because the lens of your eye can act like the lens of a magnifying glass. Just like you can burn ants with a magnifying glass in the hot sun, you can sunburn the back of your eyes by staring at an eclipse. Even without heat, you can sunburn yourself with snow or water, because they reflect light.
Kron pointed out that, just as everyone has a dominant hand, so too does everyone have a dominant eye.
People can be left-eyed or right-eyed, Kron said. Hold out your hands in front of you, so that theyre covering some object in the distance. Close one eye, then the other. When you close one of your eyes, youll see that object jump out from behind your hands. Most of the time, your dominant eye is the same as your dominant hand.
Our students have been learning how the eyes interact with the brain, Barnard said. They really took the time to formulate good questions for this program. We dont normally go this deep.