Anatomy of the Eye
The visible part of the eye is called the eyeball.
The eyeball is a sphere, approximately 2.5 cm in diametre.
To simplify the complex and sophisticated structure of the eye, it can be compared to a camera, which is based on how the eye functions.
Light passes through the clear transparent cornea, which is like the lens, into your eyes, the camera.
The iris acts as the diaphragm of the camera. It expands and contracts according to the brightness of the light and so controls the amount of light entering your eyes. This is done by controlling the size of the pupil, which is akin to the aperture in the camera.
The brighter the light, the more it contracts. In dark conditions, the pupil becomes large, or dilated, to admit more light into the eye.
Light passes through the media or the cornea, aqueous, pupil, lens and vitreous to focus on your retina, which is equivalent to the photographic film. As with a camera, to obtain a good image, it is necessary that all the media be clear.
Depending on the distance of the object from the eye, the lens can become flatter or thicker to focus the object’s image on the retina. This process is known as accommodation.
The optic nerve carries the information of the image of any object, to the occipital cortex of the brain, where the centre for sight is located. Here the message is interpreted and you “see” the object.
When any of these components of the eye does not function in its full capacity, sight is affected. The degree of visual disability is determined by how severely these components of the eye are affected.