How Our Eyes See

In order to see, light must enter our eyes. It starts with the eye muscles moving the eyeball to point at the object that we want to see. The light rays enter our eyes through the cornea. This clear thin curved layer protects the eye and begins to refract (bend) the light as it enters.

The refracted light then passes through the pupil (the black spot in the middle of the eye). The iris (the colored area around the pupil) controls the size of the pupil by contracting or expanding depending on the amount of light it needs to see the image. If it is bright, the iris expand to make the pupil smaller, and if it is dark, the iris contracts to make the pupil bigger.

The light then enters the lens which bend the light farther to focus the image. The lens’ shape is controlled by the ciliary muscles which contracts to thicken the lens to bend the light more, and relaxes to flatten the lens to bend the light less. The thickening and flattening of the lens to refract the light is called “accommodation”.

The accommodated light leaves the lens and goes through a clear fluid called the vitreous humor before reaching the retina. The retina is a light sensitive membrane that lines the inner eyeball. The membrane has millions of light receptors (photoreceptor) that gathers the information and pass it to the optic nerve. The optic nerve sends the data to the brain to process into the image we see. This completes the process of seeing.