In Our Eyes

Have you ever wondered how you see things? Our eyes can admire great mountains in the far off distance, or examine a book at a coffee shop. But how can our eyes process such things? Our eyes are constantly responding and refocusing according to our surroundings and light adjustments.

To focus on a candle, the image must first travel is the cornea, which is a transparent fluid found at the very front of the eye that helps us adjust to different medium of light. The cornea also covers the iris and the pupil. The iris contains the ring of color around the eye, and the pupil, the is black center. The pupil reacts to the light of the surroundings; it controls how much light is entering the eye to focus on the candle.

Right behind the pupil lies the lens, which focuses on the candle and is the window that feeds it back into the nervous system to the brain. The ciliary muscles surround the lens, and these muscles control the movements of your eyes focusing on the candle. These muscles also have another job. When the ciliary muscles relax, the lens flatten, which allow you to see objects in the distance surrounding the candle. When the ciliary muscles contract, the lens thicken, which allow the user to see the candle clearly at a closer range. If someone is having trouble with vision, like myopia (nearsightedness) or hyperopia (farsightedness) it usually deals which a contraction problem in the ciliary muscles that control the lens. As a person grows older, they often need glasses because the lens gets denser with age, and it gets harder for the ciliary muscles to control the lens.

The inner chamber of the eye is filled with tissue call vitreous humor. Light travels through the cornea, which reflects light, through the pupil which processes how much light goes through the eye, through the vitreous humor tissue to the retina. The retina, is sandwiched between the inner vitreous humor tissue and the outer ciliary muscles. The retina then processes the information and sends it to the brain, it is the final picture of the candle.

But there are three parts to the retina. The outermost layer, the sclera, is what gives the eye it's white color. It covers the outer eye and surrounds the cornea, the iris, and the pupil. The middle layer is its the choroid, the little veins seen around the eyes, and it's job is to supply the eye with nutrients, and oxygen, and removes waste products. The choroid is affected when its tired. When the eyes are stressed it means that your eyes are not getting enough nutrients and oxygen to keep up with the images it is receiving, thus the choroid can induce the blurriness of vision. Finally, the third and final layer of the retina is split into two parts: the rods and the cones. Rods and cones are situated right eyeball. Rods are used when we are placed in poor lighting, while cones are used for color and fine details.

Finally the details from the rods or cones are transferred to the brain via the optic nerve through electrical signals. That is how you see a flickering candle.

Read more at: http://www.webmd.com/eye-health/amazing-human-eye