How Does Human Eyesight Work?


Quick Answer

Communication between the eye and the brain in order to represent external stimuli as images is the key to human eyesight. The visible part of the eye is where the process of eyesight begins.

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Full Answer

There has to be light for humans to see. Light reflects off an object and enters the human eye. The light first touches a thin layer of tears coating the front of the eye, and then passes through the cornea. The cornea is the front window of the eye and helps to focus light, according to WebMD.

The colored circular membrane behind the cornea is called the iris, and it controls the amount of light that can pass through the pupil deeper into the eye by becoming wider or narrower, which then changes the size of the pupil. The pupil is the small black circular opening in the centre of the iris.

Once the light has passed through the pupil, it goes through to the lens, which changes shape to further bend the light rays and focus them on the retina. The retina is a thin layer of tissue at the back of the eye containing millions of small light-sensing nerve cells, called rods and cones. Cones provide clear, sharp central vision, and also detect color and fine details. Rods provide peripheral vision, allow the eyes to detect motion and help humans to see in dim light. All of these cells in the retina convert light into electrical impulses, and the optic nerve then sends these impulses to the brain where an image is produced, notes American Optometric Association.

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