The Window to the World - Vision
Written By Krish Patel
When you open your eyes and look around, you see colors and shapes, which make up a plethora of different objects and organisms. If you have glasses or contact lenses, trying to see without them makes shapes and colors blur, manipulating and hindering the sight of everyday things. How can the same objects and organisms look so different per person or any other sight-abled creature? The answer lies in the science of vision.
The Eye
Understanding vision starts with understanding anatomy of the eye that is crucial to vision. The eye has a sort of spherical form. The inside layer that stretches across the back hemisphere of the eye is called the retina. A barrier-like structure called the iris restricts some light coming through the lens, and the lens, a structure behind the iris, refracts light. The lens is concave, so that instead of being stagnant, it can adapt and refract light in different directions. The cornea is a protective layer that refracts light, making it go past the iris and lens to the retina. Light signals use the optic nerve to make their way to the brain.
How it Works
Vision uses a fairly simple process that relies on refraction, or the bending of light. Light rays travel straight and do not curve, so refraction manipulates the angle which the light is traveling, causing it to bend. Light reflected from an object makes its way towards your eye, entering through the cornea, where it bends into the lens past the iris, which controls how much light is let in. Light is bent through the lens to focus on the retina around the center, near the macula. Rays of light that enter through the top of the lens hit the retina at the bottom and rays that enter through the bottom of the lens hit the retina around the top. This results in an upside down transmission, which your brain flips. But wait, how does the brain interpret the light? The retina is composed of photoreceptors in the shape of cones and rods. The photoreceptors interpret light and convert them into electrical signals for the brain to piece together. Cones are primarily used to detect colors and for central vision while rods are mainly used in the dark and are used for side vision. Electrical signals from the photoreceptors travel using the optic nerve to get to the brain for interpretation. The brain puts together the signals to form an image, and sight is achieved!
Vision Problems
Now you know that vision involves bending and refracting light to hit photoreceptors that send signals to the brain, but why can this process result in blurry images for some? The point where light is most directly refracted onto the cornea is called the focal point. In people with nearsightedness, the cornea is too curved, refracting light into a focal point that is in front of the retina, making the sharp image also in front of the retina. This causes blurriness, especially for images and objects that are farther away. Far-sightedness is the opposite, where the cornea is curved too little resulting in a clear image past the retina. Far sight is generally good, but near sight becomes blurry. Both of these types of vision problems can be fixed by contact lenses or glasses. Both contact lenses and glasses are lenses, and they refract light to the correct position on the retina, allowing sight to be possible and clear. When your vision seems blurry, no matter far or near, it could be a sign that you need correction for your vision to see properly.
Works Cited
Page Baluch, Ashleigh Gonzales. (2015, July 01). Do You Need Glasses?. ASU - Ask A Biologist. Retrieved September 5, 2023 from https://askabiologist.asu.edu/do-you-needglasses
Seltman, W. (Ed.). (2021, November 24). How the human eye sees. WebMD. https://www.webmd.com/eye-health/amazing-human-eye
U.S. Department of Health and Human Services. (2022, April 20). How the eyes work. National Eye Institute. https://www.nei.nih.gov/learn-about-eye-health/healthy-vision/how-eyes-work#:~:text=When%20light%20hits%20the%20retina,into%20the%20images%20you%2
Waterman, A. C., & Baker, A. C. (n.d.). Eye anatomy 101. Dr. of Optometry. https://libertyoptometry.com/articles/general/418099-eye-anatomy-101
