Sometimes we take for granted the automatic functions performed by our senses every day. There’s a lot at work every time we open our eyes, so let’s take a look at the science of sight.
Eyes – Windows Allowing You to See Out, and Others to See In
Our eyes do a lot more than let us see; they let others see us. How? Our eyes can convey to others the emotions that we’re trying to hide. It’s why the eyes are often referred to as windows to the soul. Much like actual windows, the eyes give others a look inside. After we learn more about how eyes work from a scientific perspective, we’ll dive into how they function from a psychological point of view.
What Determines Vision?
Have you ever wondered what determines vision? How come some eyes can see well without corrective lenses, while others can’t? There are a number of factors that affect vision, including the cornea, the lens, and genetics.
Common vision problems are myopia (nearsightedness), hyperopia (farsightedness, and astigmatism. All are caused by light refraction disorders in the eye. Thankfully, there are surgeries that can correct vision problems, whether they’re genetic, or due to old age. LASIK, photorefractive keratectomy, implantable Collamer lens, and even cosmetic eye surgery can improve vision problems unrelated to eye disease.
Components of The Eye
In order for the eye to see, there needs to be light. Light is the catalyst the allows all the following components of the eye to work together and process an image.
The eyes may be the window to the soul, but the cornea is the window to the eye itself. This is a clear covering on the eye that allows light to pass through. If misshapen, it can affect one’s vision, requiring corrective lenses or surgery.
Behind the cornea is the anterior chamber, which houses aqueous humor. This liquid is clear and watery.
The whites of the eyes are called the sclera.
This is the colored part of the eye, and it helps dilate and constrict the pupil.
The actual opening of the eye is the pupil.
Behind the pupil is the lens. When light enters the eye via the pupil, it’s directed to the retina via the lens. It’s a transparent component of the eye and can be surgically replaced if it deteriorates to the point where corrective lenses (glasses, contact lenses) no longer improve vision.
The eye is filled with a clear, jelly-like substance called the vitreous humor.
The back of the eye is lined with the retina, with is a layer of nerves. It senses light and creates the electrical impulses the optic nerve will carry to the brain to convey images. When the retina receives visual information, the image on the retina itself is upside down.
Located between the retina and the sclera is the choroid. This is a layer of blood vessels.
Within the retina, the macula contains light-sensitive cells. Their job is to help us see detail.
In order to see color, we have photoreceptors in the retina tissue. The cones and rods work together to interpret light wavelengths so our brain can identify the color. Cones help us see colors such as red, green, and blue. Rods help us see black and white. Cones are located in the fovea of the eye, which is in the center of the retina at the back of the eye.
The optic nerve is actually a bundle of over a million nerves that convey information to the brain so we can make sense of the information received by the eyes. Once an image is sent to the brain, it’s no longer seen as upside down.
More Than Just Vision
While the origin of the quote, “The eyes are the window to the soul” is unknown (it’s attributed to Shakespeare, Cicero, and the Bible among others), its meaning is pretty clear. Eyes are expressive and can betray what we’re thinking or feeling.
Psychologists Sebastiaan Mathôt and Stefan Van der Stigchel published an article in Current Directions in Psychological Science discussing how the size of one’s pupils directly relates to their emotional state.
Many of us already know that our pupils change size in response to light. Like the aperture of a camera, our pupils dilate (get bigger) to let more light in when it’s dark, and they shrink to block light when it’s bright. Mathôt and Van der Stigchel argue that the body’s autonomic nervous system triggers pupil dilation and constriction in response to stimuli other than light.
For example, in a situation of fight or flight, when you have to choose to respond to a perceived threat, the sympathetic nervous system triggers pupil dilation. There has been no change to the amount of light available to you, yet your body opens the pupils in an effort to enhance your vision and increase your chances of survival. Additionally, pupils are known to dilate during arousal due to the hormones oxytocin and dopamine. In times of heightened anxiety, the “stress hormone” cortisol can cause a pupil to restrict.
So while you probably can’t tell if someone is telling a lie just by looking them in the eyes, you can tell if they’re scared, aroused, or anxious by noting the size of their pupils.
Tips for Healthy Eyes
Remember when your parents told you to eat carrots to improve your vision and to avoid sitting too close to the TV? Well, while it’s true the vitamin A in carrots is good for your eyes, you’d have to eat a lot every day to significantly improve your eyesight. Here are some proven tips for healthy eyes.
Eat a Balanced Diet
A good mix of foods can promote good eye health. Be sure you’re including sources of omega-3, lutein, and protein in your diet. Vitamins B and C are also good for your eyes.
For overall health, exercise should be a part of your daily life. It can prevent diabetes, which increases the risk of glaucoma, which is a disease that damages the optic nerve and can lead to blindness.
Wash Your Hands
Did you know diseases that affect vision can be spread via your hands? Just another reason to spend at least 20 seconds sudsing up every time you wash your hands.
Clean Your Contact Lenses Properly
If you wear contact lenses, be sure you’re not only washing your hands properly, but the lenses ad their case as well. Only wear your lenses for the prescribed length of time, and never use expired cleaning solution. Be sure you’re regularly sterilizing your storage case, and keep all your contact supplies in a clean place when not in use.
Wear Protective Glasses
This applies to both sunglasses to protect against UV and UVB rays, as well as glasses to protect your eyes while working with hazardous materials or potential projectiles. If you spend a lot of time looking at screens, consider wearing blue-light blocking glasses.
Did you know smoking can increase the risk of macular degeneration and cataracts? Smoking can also cause damage to the optic nerve and increase blood pressure, which can harm the retina.
Taking good care of your eyes not only helps you see the world better, but it can help others see you better.