How Eye Works?
The human eye is a window to the real world. It represents a gateway to the process we call vision.
How do we see?
In order for vision to take place, a succession of processes must occur involving the structures within the eye and the brain:
The first part of this chain is that light rays must travel through the eye to ultimately focus on the retina. Light first passes through the clear cornea at the front of the eye, and then aqueous humor. As light continues on its pathway it passes through the pupil, a round opening in the center of the iris. The next structure light penetrates is the lens, a clear and multilayered structure shaped like a large lentil (about 10 mm in diameter). Once through the pupil and lens, the light then passes through the larger posterior (back) portion of the eye and falls on the retina, where the specialized cells known as rod cells and cone cells are stimulated to set off a chain of split-second chemical reactions converting light to electrical impulses. Finally these electrical impulses are transmitted to brain by optic nerve. The brain’s interpretation of the electrical impulses sent by the optic nerve is very important for a person to see.
When all parts of the visual system are working, both eyes work in co-ordination; they can adapt to light and dark, perceive color, contrast and accurately evaluate an object’s location in space. By convention, we know “normal” visual acuity is reported as 20/20.