In this particular episode of Ask an Eye Doc, you will learn:
- How the pupil of the eye is like the aperture of a camera
- How squinting affects the aperture size of the eye
- How increasing or decreasing aperture size affects depth of focus
- How to rid yourself of squinting for good!
This episode will make more sense if you’ve already listened to episode 19 about the iris and the pupil.
For you readers out there, here’s the answer in written form:
Today’s question was submitted by Matthew. He asks why he can see distant objects better when he squints? What is it about squinting that allows him to see more clearly?
Thanks, Matthew for submitting your audio question through askaneyedoc.com/question! This is a question I get fairly frequently from patients.
If you want to perfectly understand why squinting allows you to see more clearly, you’ll need to know optics, a branch of physics that explains the properties & behavior of light.
Since I’m not much of a physics professor, I’ll address this question from a different angle. If you know a bit about photography, you’ll find this answer to be useful. If you’re not a photographer or a physicist, you’ll just have to have faith that this is how optics works.
All about aperture
Remember in episode 19 we talked about the iris and the pupil? The pupil is an aperture, or in other words, a hole or opening. The size of the aperture determines how much light enters your eye.
If you’re a photographer, you know that increasing the aperture size of your camera decreases its depth of focus. This means that only objects a certain distance from the camera will be in focus. I’m sure you’ve seen those artsy photos that have an in-focus object or person and blurry backgrounds. Photos like those are created by increasing your camera’s aperture size.
Decreasing the aperture size has the opposite effect and increases the depth of focus. With an increased depth of focus, most objects in the photo will be in focus regardless of how far away they are from the camera.
Optics is true for both cameras and for human eyes. When you squint, you are essentially decreasing the aperture size of your eyes and increasing your depth of focus. For example, if distant objects are blurry, squinting will help you when looking far away. You may notice your vision is dimmer (because less light enters your eye), but the clarity is better.
So now you know, Matt, why squinting helps you see more clearly! But I don’t want you to squint anymore… it causes eyestrain (and wrinkles). You can rid yourself of squinting for good by scheduling an eye exam with your local optometrist. He or she will help you see clearly without squinting. Your eyes will thank you for it!
Thanks for the question!