p6

• Light passes through a transparent layer called cornea
• After cornea, it passes through the lens, the major focusing structure.
• The lens is held in place by suspending ligaments to ciliary muscles.
• Contraction of ciliary muscles changes the shape of the lens and thus the focal point.
• The iris, located between the cornea and the lens, controls the amount of light entering the eye.
• The retina, in the back of the eye, contains about 3M cones which detect color, and 1B rods, which detect light and dark.
• The central region of the retina where images are focused is called the fovea
• The optic nerve transmits visual impulses directly to the brain.
• People whose point of focal lies in front of the fovea are near-sighted
• People whose point of focal lies behind the fovea are far-sighted.
• Corrective lenses may be used to focus the image onto the fovea, thus correcting the condition.
• The iris reduces the size of the transparent zone, or pupil of the eye.