Eyes Flashcards
Lens
Refracts light by controlled amount by changing shape
Iris
Controls pupil size/ amount of light entering the eye
Cornea
-Refracts light (always by same amount)
-Transparent with no blood vessels to allow light to pass through
Optic nerve
Receives impulses generated by receptor cells and transmits them to the brain
Retina
-Contains cone cells (responsible for colour vision) and rod cells (detect intensity of light)
Fovea/ focal point
-Point on the retina where the light rays diverge together/ meet
-Contains cone cells only
In bright light the iris…
Constricts/ the pupil becomes smaller to let in the correct light intensity
-circular muscles contract and the radial muscles relax
In dark light the iris…
Dilates/ the pupil becomes larger to let in the correct light intensity
-circular muscles relax and the radial muscles contract
To accommodate to a close object the lens…
Becomes short and fat to refract rays more
-ciliary muscle contracts and the suspensory ligaments slacken
To accommodate to a distant object the lens…
Becomes long and thin to refract rays less
-ciliary muscles relax and suspensory ligaments are pulled taut
Cataracts
-Lens becomes cloudy
-Treat with artificial lens
Short sighted- myopia
Can only focus on close objects as lens refracts too much
Long sighted- hyperopia
Can only focus on distant objects as lens can’t refract rays enough
How is long sightedness treated?
-CONVEX lens to refract rays MORE so they meet on the retina
How is short sightedness treated?
-CONCAVE lens to refract rays LESS so they converge on the retina
