Eyes: How Do We See?

portrait photo of an adult black pug

Most animals you can think of have eyes that help them process their environment. Eyes are one of the major senses of animals and without them, it is imminent that they will die in the wild. So, how does the eye work?

First, it is important to understand the anatomy of an eye. The light that is reflected off an object will first enter through the cornea. The cornea is the outer layer of your eye that helps focus light so you can see clearly. This clear layer is vital for proper vision and a deformity of the cornea will result in astigmatism (an irregular curve of the cornea).

After traveling through the cornea of the eye the light will pass directly between the iris in an area known as the pupil. The pupil is the dark center of your eye and the iris is the colored outer ring of your eye (brown, blue, etc.). The iris is responsible for adjusting to the intensity of the light. This means that if you were to look at an object that reflects a greater amount of light your pupils will constrict and limit the amount entering your eye. The opposite would happen in a dark area. This assures that the image being processed is not unseeable by brightness or darkness. A fun fact about your pupils is that both pupils will dilate and constrict together. This is called the pupillary reflex and is caused by the eyes connecting afferent (going towards the brain) nerves.

After passing through the pupil the light will then be focused for a second time by the lens. This lens works in conjunction with the cornea to assure that the light hits the retina correctly. Due to the light being focused twice by the cornea and lens the light is flipped upside down at this point. This image will be inverted again later.

When the light finally passes through the lens it travels through a clear gelatinous fluid called the vitreous. The vitreous is responsible for maintaining the shape of the eye as well as preventing damage to the retina. After passing through this fluid, light is projected onto the retina. The retina contains photoreceptors called rods and cones. Rods are responsible for processing stimuli at low levels of light. They do not process color and have low spatial acuity (ability to process 2 stimuli at a close distance). The cones are responsible for processing stimuli at high levels of light. They can process color and have high spatial acuity.

These rods and cones will send afferent signals back to the brain via the optic nerve. The brain will process this information in the optic lobe and flip the image so you can see it correctly.

Published by pensmenger

I am a Biology Major attending Arcadia University. I started the company My Biology Experience in hopes to connect the Biology community on a closer level.

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