Eyes are a very complex part of the human body. An eye has several major components: the cornea, pupil, lens, iris, retina and sclera. They work together to capture images and transmit them directly to the brain’s occipital lobe using the optic nerve. When we look at an object, light is reflected from that object and enters the eye. This light is then refracted, which creates a focused, upside-down image of the object that the brain will have to interpret and turn in the correct direction.
The retina is a layer of light-sensitive cells that line the inside surface of the eye. Inside this photosensitive layer there are specialized cells called photoreceptors. Photoreceptors create nerve impulses when struck by light. There are two types:
Cone Cells – make color vision possible and work best in bright light
Rod Cells – are more light-sensitive, transmit black-and-white images, and allow us to see in dark conditions
Human eyes are able to determine distances and depth because information from both eyes, right and left sides is sent to separate areas of the brain for interpretation. The brain recombines this information to create three-dimensional image.
There are a series of muscles the help the eye move. The first set of muscles is the superior and inferior rectus muscles, which allow upward and downward motion. The medial and lateral rectus muscles allow the eye to move from side to side while staying level. The superior and inferior oblique muscles let it move up or down and to the side. Most of these muscles are controlled by the oculomotor nerve.
Friction from these movements would quickly damage the eye without lubrication. Tears released by the lacrimal glands (tear ducts) provide this. These are spread around your eyes by blinking. Tears also help remove foreign objects and bacteria that could cause damage to your eyes.