In Depth: Eye
Eyes are roughly one inch in diameter. Pads of fat and the surrounding bones of the skull protect them.
The eye has several major components: the cornea, pupil, lens, iris, retina and sclera. They work together to capture an image and transmit it directly to the brain’s occipital lobe via the optic nerve.
When we look at an object, light reflected from it enters the eye and is refracted. This creates a focused, upside-down image of the object that the brain will have to interpret and turn in the correct direction.
Inside the eye are photoreceptors, which create nerve impulses when struck by light. There are two types: Cones makes color vision possible, and rods specialize in black-and-white images.
Human eyes are able to determine distances and depth because information from the eyes’ right and left sides is sent to separate areas for interpretation. The brain recombines the information to create three-dimensional vision.
A series of muscles helps the eye move. The first set 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 provide this. These are spread around by blinking. Tears also help remove foreign objects and bacteria that could cause damage.
Among the afflictions of the eye is color blindness. This condition, which is more prevalent in men, is caused when an individual lacks some or all of the photoreceptors that see color. Other conditions include glaucoma, nearsightedness, farsightedness, blindness, and others.