The eye is an organ that specializes in sight or helping an individual to see. The simple proteins and cells in the eye allow the individual to tell day and night (light and darkness) apart. The eye comprises complex assemblies of nerves, filters, light-sensitive tissues, supportive structures, and lenses. Earth Vision Eye Care, www.earthvisioneyecare.com explains that humans and other animals have highly-specialized visual systems. Animals gather light through their eyes and use it to achieve complex visual processing. For instance, mammals use a lens and retina to collect light rays and relay that information to the brain for interpretation. In contrast, insects boast compound eyes with several separate lenses for light gathering and a mosaic-like view of objects.
Below are parts of the human eye as well as the functions performed by each part.
The Cornea: The journey of light into the eye starts at the cornea, which is a layer consisting of transparent tissue resting on top of the pupil and iris. It focuses light to help generate the clear image displayed on the retina. It also forms an additional protective layer.
Pupil: This part of the eye seems black because it allows light to pass through without returning. It acts as the passage through which light enters the eye for further processing.
Iris: This is the colored ring surrounding the pupil that contains a sphincter muscle that expands and contracts to control the size of the pupil and make it larger or smaller. It enables the eye to control the amount of light entering the inner parts.
Lens: Once light passes through the pupil, it is focused by the lens for a clearer view. This part of the eye is located immediately behind the pupil and refracts light constantly, just like the artificial lenses found in glasses do. The “adjustable” lens changes the focus based on the distance of the object from the eye.
Retina: The eye is spherical, and the retina lies at the back of it, directly opposite the pupil. With light-sensitive cells, it can tell colors and levels of brightness to assemble images. It converts this information into neural codes of information before relaying to the bran for further processing.
Optic Nerve: It comprises neural fibers bundled together and traveling from the back of the eye to the brain. Its function is to encode the image information collected by the retina to form neural signals to be interpreted by the brain.
The Conjunctiva: This clear, protective membrane on the eye surface is lubricated to enable the eye to function properly. The substances contained in the conjunctiva include a watery solution, mucous, and oils to prevent drying of the eyes and possible surface irritations.
The Sclera: This whitish part of the eye does not ideally collect image data, but instead protects the eyeball.
Vitreous Humor: This is the thick, jelly-like fluid part that covers the eyeball and constantly refracts light. This part is responsible for the round shape assumed by the eye. Any change in the shape of the eye due to lacking vitreous humor may lead to improper focusing of the light and possible vision problems.