Glaucoma

What we know as light is actually a tiny portion of a vast spectrum of electromagnetic waves. Objects either give off or reflect light. We perceive an object when its light waves enter the eye and an image of the object is focused on the retina.

The lens and the cornea comprise the optical system and are similar in function to the lens of a camera. Both play a role in bending and focusing light rays. In the eye, the image is focused on the retina, which is the thin layer of light-sensitive tissue lining the back of the eye. In a camera, the image is captured on film, which is also a photosensitive surface. The retina, however, is much more elaborate since a great deal of complex information processing takes place here. It is considered the first of a series of steps in the pathway to vision. To begin with, the receptors in the retina, called rods and cones, absorb light, which in turn leads to their activation. These receptor cells are connected to other cells that aid in the transport of the information. The output from the retina is via special cells whose ends form the optic nerve. This helps the optical message travel to the thalamus, where it is then passed along to the part of the brain responsible for vision, thus enabling us to see.

Did you know that?When we look at an object that has more than one dimension, the image formed on the retina is upside down and also reversed right to left relative to the original object.