The eye is the organ of vision. From a physiological point of view, vision is a process of sensorial perception which captures our outside environment and transforms it into internal images that can be interpreted by our brain.
For our eyes, the outside world, its shapes and its colours are made up of light rays. Once detected, these rays converge within the eye to project onto a limited area of the back of the eye, an area that works like a projection screen on which the images are formed then transmitted to our brain.
Four basic elements of the eye participate in this process:
To a great extent, the eye can to a great extent be likened to an optical instrument. But this instrument may experience some defects which cause vision problems. The most well known are short-sightedness or long-sightedness.
When vision is normal, we are emmetopic. In this case, and as the figure shows, the light rays are perfectly focused on the retina.
Whereas, in the case of short-sightedness, when you see better close up than far away, the eye is too long, and the light rays meet up in front of the retina.
Lastly, in the case of long-sightedness, where you see better far away than close up, the situation is reversed: the eye is too short, and the light rays meet up behind the eye.
The optical defects of the eye can be corrected