The Human Eye
Sight is one of our five senses. It helps us to interpret our world by taking in information from our surroundings. The eyes perceive movement, colour, shape and more. This aids us in our ability to function in our everyday lives.
The human eye is a complex organ that detects light. It is the reflected light of objects that we perceive as images. As light enters the eye through the cornea, the transparent, curved part of the eye responsible for seventy percent of the focusing of the eye, the light is bent, creating an upside-down image on the back of the retina. The brain then reverses this upside-down image, right-side up.
The eye has special parts to keep it healthy and safe. The eyelid protects the eye by opening and closing a few times a minute. This blinking enables the eye to remain both moist and clean. As well, the eyelashes in conjunction with the eyelids work together to help to eliminate unwanted dirt and debris from entering the eye. Tears that are produced by the lacrimal glands, which are located above the outer corners of the eyes not only help to maintain the eye's moisture balance, but they help to wash away germs and other dust and particles that would harm the eye.
It is important to keep your eyes well protected. One should always wear safety goggles in environments where potential chemicals and debris could make their way into your eyes. When playing sports such as hockey, skiing and racquetball make sure that eye protection is always worn. Also, don't forget to wear your sunglasses. Extensive exposure to the sun's rays could lead to vision problems.
Basic Parts of the Eye
Cones: These are specialized cells found at the back of the retina. There are approximately seven million cones in each eye. The cones require more light than the rod cells to work well. The cones are responsible for daytime vision. They allow us to see objects in detail. As well, they enable us to see in colour. There are three types of cones, each sensitive to one of the following colours: red, green or blue.
Cornea: It consists of a clear tissue that is usually half a millimetre thick. The cornea sits in front of the iris. The cornea aids in the focusing procedure as the light passes through. It is the most important layer in the refractive procedure.
Iris: The iris is the colourful part of an eye. It is a thin diaphragm that sits behind the clear cornea. The iris contains the pupil.
Lens: This essential element works with the cornea. It, too, is responsible for refracting the light. The lens alters shape in order for focusing to be possible at various distances.
Optic Nerve: This nerve is responsible for carrying the information about the image to the brain.
Pupil: This is the black circle located in the center of the iris. The pupil allows light to enter the retina.
Retina: The retina is responsible for most of the focusing (70 %). The back of the retina consists of a layer of light sensitive cells (rods and cones). The image is projected at the back of the retina.
Rods: These cells, of which there are roughly 120 million in each eye, are concentrated at the back of the retina along with the cones. They are helpful in night vision.
Sclera: This is the white part of the eye.
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