The day I got my first pair of glasses, everything suddenly sharpened; I could see all these details and signs I hadn’t realized were blurry. Other than being nearsighted, I had also found out I had astigmatism.
The outer layer of our eye consists of the cornea. The cornea is transparent and covers the iris and pupil. The iris is the colored part of our eye, it’s what indicates whether we’re blue-eyed or brown-eyed. It’s also the muscle that controls the size of our pupils: when we’re in a dark environment, the iris will cause our pupils to dilate to try to get more light in, and when we’re in a bright environment, our pupils contract to limit the amount of light from coming in.
Thus, our pupils are just holes at the center of the irises. They are black because the light rays that enter the pupil are absorbed by the tissues within our eyes (meaning nothing is reflected back for us to detect any kind of color from the pupils).
Behind the pupil and iris is the lens. The lens bends and focuses the light entering the pupil. It shapes itself, refracting the light and having it converge onto the retina (located at the back of our eye). This aids in letting us see objects at different distances. The lens is made up of mostly proteins and is transparent, allowing light to enter the rest of the eye. Because the lens is convex (curved outwards), the image that’s formed on the retina is upside down and left to right (i.e. inverted and reversed).
The retina then turns the light entering the eye into electrical signals and these signals are sent back up to the brain. The brain rights the image and puts it in the correct direction, allowing us to perceive the world through our sense of sight.
A lot of things can affect this deceivingly simple process, one thing being the shape of our eye. If our eyes are too short (hyperopia), the light that’s refracted ends up focusing behind the retina and causes objects that are closer to us to appear blurry and objects that are further away to appear more clear. If our eyes are too long (myopia), the light refracts in front of the retina (rather than on it), causing further objects to be blurry and closer objects to be clearer.
When we’re born, we’re typically hyperopic. As we grow older, our eyeballs lengthen until they become spherical. However, our eyeballs can keep growing, forming a more football-like shape, and causing myopia.
The recent increase of myopia among the population is most likely due to the lack of sunlight our eyes receive. When our eyes encounter sunlight, they release dopamine. The release of this neurotransmitter decreases the progression of myopia. Because people have been spending so much time indoors (be it for school, work, doing homework, or on their screens), their eyes have been experiencing much less sunlight.
Astigmatism has to do with the shape of the lens of our eyes. If the lens has an irregular shape, light is refracted unevenly (versus in the eyes of someone with a normal lens, the light would be refracted more uniformly). For individuals with astigmatism, the uneven refraction of light results in many different focal points in front of, behind, or on the retina. This causes objects that are both close by and further away to be blurry and essentially, light scatters and focuses at different points. This causes light rays to appear spread out, forming streaks, which can be especially prominent during nighttime driving. Astigmatism is mostly genetic, there doesn’t seem to be environmental factors that cause it.
Understanding how the shape of our eyes/lens causes such significant changes is vital in understanding visual perception.
VAAGEESHA DAS is a second-year college student and columnist for The Dominion Post. Information comes from: Here’s how social media affects your mental health | mclean hospital. Putting People First in Mental Health. (n.d.). https://tinyurl.com/genovsm; Unplugged. (2024, March 20). Why we cant stop mindlessly scrolling and 7 tips to beat it. https://tinyurl.com/infscrollgen; Boyd, K. (2024, May 10). What is astigmatism? symptoms, causes, diagnosis, treatment. American Academy of Ophthalmology. https://tinyurl.com/astigart; Sprabary, A. (2021, February 24). Lens of the eye. All About Vision. https://tinyurl.com/anateye; Vox. (2023, March 7). Why so many people need glasses now. YouTube. https://tinyurl.com/vidmyopia
