subject: The Human Eye -a Deeper Look [print this page] The human eye is an organ which reacts to light to allow us to see things. Our eyes help us in every activity we perform during the day. The eye has several different structures to it. These structures include the extraocular muscles, cornea, crystalline lens, iris, conjunctiva, optic nerve, macula, vitreous, and the retina. Each of these structures work together to allow the human eye to give us a sense of physical things around us. The extraocular muscles are what turn and rotate the human eye to its vertical, horizontal, and antero-posterior axes. The cornea is the outer window of the eye which focuses on any light that enters the eye. The crystalline lens is what changes the human eye pupil from big to small and vice versa. The iris is the pigment in your eye that makes up your eye color. The conjunctiva is the clear mucous membrane that lines the inner surfaces of the human eye and the front surface of the eyelid except for the cornea. The optic nerve is nerve tissue which connects the human eye to the brain for function. The macula is what provides clear and distinct vision. The vitreous is a gel that occupies the posterior compartment of the human eye. The retina sends impulses through the eye to the brain and sends it back which shows up as the images that we see.
The human eye size starts from eighteen millimeters during infancy to about twenty four millimeters at adulthood. There are three common refractive errors that many people get such as myopia, hyperopia, and astigmatism. After the age of forty some people are at risk to develop presbyopia. Presbyopia is a condition that makes it harder to see things up close rather than farther away.
