Peripheral vision is your bodies ability to see movement and objects outside of your direct line of sight. But how exactly does it work?
The cells that allow you to see come in two types, cone cells and rod cells. Cone cells work well when trying to make out the fine details in objects or people. When you’re looking directly at an object, you’re using what’s known as ‘central vision’
Rod cells are responsible for peripheral vision. They are located outside of the retina, and are best suited for picking up movement instead of fine details. Peripheral vision is an evolutionary trait that early humans developed in order to spot any predators trying to sneak up on them. Thankfully, most people don’t need to worry about surprise predator attacks anymore and yet modern day humans still have peripheral vision.
It has evolved from warning you about potential predators, to alerting you when a person or object is entering your proximity. Peripheral vision now helps humans avoid potential accidents when walking, riding a bicycle, or driving a car.
Tunnel vision is a condition in which a persons peripheral vision is weakened. This can be caused by a variety of different factors such as eye strokes, or concussions. If caught early enough, doctors can help prevent further rod cell loss with either glasses or eye drops.
Doctors use a variety of different test to check the health of your peripheral vision. The easiest, and most common test is called Confrontation Visual Field. In this approach, you sit in front of a doctor with one eye covered. While staring straight ahead, you have to notify the doctor as soon as you see their hand moving from the side of your head towards the center. If you notice movement right away, your peripheral vision is in good condition. However, if you struggle to pickup on any movement, your rod cells may be deteriorating, and you may need eye drops or protective eyewear to prevent further vision loss.
Humans aren’t the only creatures to utilise peripheral vision. For example, goats have the ability to see nearly everything around them. Their rectangular shaped pupils give them a 320-340 degree field of vision, whereas humans only have a 120 degree field of view.