the eye

• the retina is at the back of your eye and contains rod and cone cells
• rod cells are sensitive to light
• cone cells are sensitive to color
• the fovea is a point in the retina which contains the highest concentration of cone cells
• the iris is the colored part of the eye that controls the size of the pupil
• the pupil is the opening of the eye that allows light to enter the eye
• the sclera is the white part of the eye and is the outer layer of the eye
• the lens is a transparent structure that changes shape to focus light onto the retina
• the cornea is the transparent layer of the eye that refracts light to focus it on the retina
• in bright light, the radial muscles relax and the circular muscles contract to make the pupil smaller
• in dim light, the radial muscle contracts and the circular muscle relaxes to make the pupil bigger
• the optic nerve carries impulses from the eye to the brain
• when looking at objects nearby, the ciliary muscles contracts and the suspensory ligaments slacken, making the lens short and fat
• when looking at far away objects, the ciliary muscles relax and the suspensory ligaments contract, making the lens long and thin
• convex lens is used to correct long sightedness
• concave lenses are used to correct short sightedness
• the medical name for long sightedness is hyperopia
• the medical name for short sightedness is myopia
• long sightedness happens when the light isnt refracted enough and the image forms behind the retina
• short sightedness happens when the light is refracted too much and the image is formed infront of the retina
• some alternatives to wearing glasses is laser eye surgery, contacts and replacement lens surgery