Notes Structure of Eye Cornea a thin transparent

• Cornea- a thin, transparent outer covering of the center of the eye;

Common eye defects: • Nearsightedness (Myopia): • The lens doesn’t become thin enough to

• Farsightedness (Hyperopia): • The lens doesn’t become thick enough to focus on

• Remember: • The shape of the cornea can also cause nearsightedness and

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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.