Focusing structures in the eye

Some of the light rays reflected off the flower reach the cornea, the clear outer covering of the eyeball. A few of these rays reflect off the cornea, but because it is clear, most rays are transmitted through it into the eye. The cornea, along with the aqueous humor, lens, and vitreous humor, refract the light rays, bending them to form a clear image of the world on the retina (as shown in the figure above).

For some young people, and almost all older people, these eye structures are not perfect image-formers. Glasses and contact lenses add refractory power and can compensate for any focusing errors in the eyes (see textbook Figure 2.5).

(The cornea, aqueous humor, lens, and vitreous humor are described in more detail in the activity on Eye Structure.)