Introduction to the Eye
The eyes are wonderful sensory organs. They help people learn about the world in which they live. Eyes see all sorts of things - big or small, near or far, smooth or textured, colors and dimensions. The eyes have many parts - all of which must function in order to see properly.
Inside the Eye
In addition to the many sections of the eyeball itself, muscles are attached to the outer walls of the eyeball. The eye muscles are attached to the eyes in order that we can move our eyes. The interactive diagram shows these main parts. If anything goes wrong, such as from diabetic eye disease, an individual might not be able to see as well.
A Complete Picture
Visual information from the retina travels from the eye to the brain via the optic nerve. Because eyes see from slightly different positions, the brain must mix the two images it receives to get a complete picture.
What we think of as seeing is the result of a series of events that occur between the eye, the brain, and the outside world. Light reflected from an object passes through the cornea of the eye, moves through the lens which focuses it, and then reaches the retina at the very back where it meets with a thin layer of color-sensitive cells called the rods and cones. Because the light criss-crosses while going through the cornea, the retina "sees" the image upside down. The brain then "reads" the image right-side up.
Iris: the colored, circular part of the eye in front of the lens. It controls the size of the pupil.
Lens: the transparent disc in the middle of the eye behind the pupil that brings rays of light into focus on the retina.
Retina: the inner layer of the eye containing light-sensitive cells that connect with the brain through the optic nerve. It also contains retinal blood vessels which feed the retina and which can be affected by diabetes.
Sclera: the white part of the eye that is a tough coating which, along with the cornea, forms the external protective coat of the eye.
Vitreous Body: a colorless mass of soft, gelatin-like material that fills the eyeball behind the lens.