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How the Eye Works

The eye has many different components that are all vital in its functioning. The way a camera works is similar to the eye’s functions: light rays are absorbed through a lens and are translated into images, either by the brain or by the mechanisms in a camera. The contractions of the iris are similar to a camera’s shutter and the retina is the equivalent of a camera’s film or memory card. The way images are interpreted and stored is based on the way the brain processes impulses from the nerves in the eye.

In essence, both a camera and the human eye require precision and properly functioning parts to create images, whether stored digitally or interpreted by our minds.

How Light Travels Through the Eye

Refraction describes the way light bends when it encounters surfaces like water or a lens. When light enters the eye, it bends in a way that allows it to focus on the retina. Roughly eighty percent of refraction occurs in the cornea; the other twenty percent occurs in the crystalline lens.

The ways in which our eyes are capable of turning light waves into images is truly remarkable. Here’s the specific science that explains how our eyes serve as our windows to the world.

Initial Refraction

The process of sight begins as soon as light waves penetrate the cornea. In this capacity, the cornea functions as a lens, causing refraction to occur at both the front and back surfaces. In this initial intake of light, multiple waves of light are concentrated into a single beam, allowing it to penetrate the interior of the eye.

initialrefraction

Regulated Entry

After light is refracted in the cornea, it passes through the aqueous humor and then through the pupil and into the lens. How much light enters the eye depends on the size of the pupil, which is controlled by the iris to regulate the amount of light permitted to reach the retina.

regulatedentry

Accommodation

After light passes through the cornea, the aqueous humor and the pupil, it continues to refract in the crystalline lens. As we previously discussed, the lens acts as a magnifying glass, flexing in a way that allows us to change focus when needed. The way the lens functions is called accommodation and is controlled by the muscles in the ciliary body.

accomodation

Projection

From the lens, light passes into the vitreous humor, the gelatinous body located behind the lens where it is focused into the retina. The image on the retina is actually inverted from what we see; our brains know how to process images so that they appear right side up.

projection

Conversion

Once light is converged upon the retina, the nerve cells translate the beam of light into electrochemical impulses. These impulses are sent by nerve cells to the brain. The brain then interprets an image using the information sent from the nerve cells within the retina.

conversion

Transmission and Interpretation

Transmission is the process of sending impulses to the brain via the optic nerve, a bundle of nerves that run from the back of the eyeball into the brain stem. Once the signals travel the optic nerve and up the brain stem, our brain interprets images from the combination of impulses.

transmissionandinterpretation

Previous: Ciliary Body

Next: Common Visual Problems