The eye

• Cornea - transparent layer of the eye that refracts light to focus it on the retina
• Iris - controls the size of the pupil, which controls the amount of light entering the eye
• Lens - Refracts light to focus it on the retina.
• Retina - The light-sensitive layer at the back of the eye. Includes cone cells (colour) and rod cells (B&W)
• Optic Nerve - carries impulses from the retina to the brain
• Bright - Circular muscles contract and radial muscles relax

  Night - Circular muscles relax and radial muscles contract

  
• Accomodation - the process of changing the shape of the lens to focus on near or distant objects
• Ciliary muscles - contracts and relaxes to change shape of lens
• Suspensory ligaments - connect the lens to the ciliary body and suspend the lens
• Fovea - The central part of the retina
• Close object - lens short and fat

  ciliary muscle contracts, sensory ligaments slacken
• Distant object - lens long and flat

  ciliary muscle relaxes, sensory ligaments taut
• Long-sighted (hyperopia) - cant refract enough

  Convex lens
• short sighted (myopia) - refracts too much

  concave lens
• Lenses

  A) Concave

  B) Convex