Notes: Structure of Eye

Cornea- a thin, transparent outer covering of the center of the eye; it provides most of the focusing power Pupil- the opening that lets the light in Iris- a pair of circular muscles that determine the size of the pupil; gives the eye its color Lens- convex; helps make a real image on the retina Retina- the light sensitive surface at the back of the eye Optic nerve- sends info to the brain

Common eye defects: Nearsightedness (Myopia): The lens doesn’t become thin enough to focus on objects far away. Or, the eyeball itself is longer than normal. Most often the cornea is too curved and bends light rays too much. As a result, the image falls in front of the retina. This affects about 1/3 of the general population. A concave lens corrects this

Farsightedness (Hyperopia): The lens doesn’t become thick enough to focus on objects close up. (older) Or, the eyeball itself is shorter than normal Or, the cornea isn’t curved enough and bends light rays too little. As a result, the image falls behind the retina. This affects about ¼ of the general population. A convex lens corrects this

Remember: The shape of the cornea can also cause nearsightedness and farsightedness. Reshaping the cornea with lasers can fix some problems LASIK is one example.