How does the eye work?
The eye acts much like a camera. Light rays from an object enter the eye through the cornea, the clear front surface or “window” of the eye.
The cornea refracts or “bends” light rays so that they pass through the pupil of the eye. The light rays passing through the pupil are then focused by the lens of the eye onto the retina (which acts like the film of a camera).
These light rays are changed by the retina into electrical signals that are transmitted to the brain via the optic nerve, which is like a “cable” connecting the eye to the brain. The brain processes these signals into “pictures” that we see.
What is eye pressure
Like a football or tyre, the eyeball also needs pressure to maintain its shape. In the eye a water-like fluid called aqueous maintains the pressure.
This fluid is made in the back part of the eye in an area called the ciliary body. It then circulates inside the eye providing oxygen and nourishment to eye tissues. It then drains out the front part of the eye in an area called the drainage angle (or ‘drainage canal’) and into the bloodstream.
Normally this fluid is made at the same rate as it is drained and the eye pressure remains stable. The eye pressure for most people ranges between10 to 21 mmHg (millimetres of mercury). However, if there is a problem with the drainage of fluid then it builds up and the eye pressure rises
What is glaucoma?
Glaucoma is the name given to a group of eye diseases in which the optic nerve at the back of the eye is damaged. This leads to vision loss because signals from the eye can’t reach the brain. In most people it is due to an increase in eye pressure because of a problem with the drainage of fluid out of the eye.