Many things we do every day require our eyesight. There are several groups of eyes, however, human eyes are referred to as camera eyes. If you think of the structure of a camera, the integral part of it is the lens which projects light onto film. It’s a similar process with our eyes. In the structure of a human eye, there is a cornea which projects light onto the retina.
Outer Eye Structure
There are three tissue layers in the eye. The deepest layer is the retina, the outlying layer is the sclera, and the middle layer is the choroid.
The sclera is the white color you see in the areas surrounding the iris. The choroid contains blood vessels which provide the retina with oxygen and nutrients.
The cornea is located at the front of the eye. The iris, a circular colored membrane, is directly behind the cornea which has the pupil in the center of it. There is a transparent liquid called aqueous humor which is found between the cornea and iris.
The pupil, located in the iris, expands and contracts to control and adjust the incoming light. Behind the pupil is a crystalline lens.
Inner Eye Structure
There are muscles surrounding the crystalline lens which are called ciliary muscles. When the muscles relax, the lens flattens resulting in the vision of faraway objects. When the muscles contract, the vision of closer objects occurs.
The tissue inside the eye is called the vitreous humor. After the light has penetrated the crystalline lens, it travels through this humor before reaching the blind spot, the retina.
The light-sensitive cells found in the retina are called rods and cones. The rods are used to see monochrome colors in the poor light. The cones are used for bright colors and fine details. The cones are located in the fovea, behind the retina, for sharper vision.
When light travels to the cones or rods, signals are sent to the brain through the optic nerve. This is what the brain uses to translate what we visually recognize. What would we do without the power of our eyesight? We can see everything in the world and accomplish more than the eye can see!