The eye

    Cards (21)

    • retina
      made up of light sensitive cells which create an image
    • Lens
      Jelly like material brigs light through to focus on retina
    • Iris
      ring of coloured muscle that controls the size of the pupil
    • Pupil
      Hole which lets different amounts of light into the eye
    • Ciliary muscles
      • control the shape of the lens
      • Contract when an object is close, lens gets fatter
      • Relax when object is far, lens is thinner
    • Optic nerve
      Carries electrical signals o the brain
    • Close objects
      CM contract , SL slacken, lens fatter , strong refraction
    • distant objects
      CM relax, SL stretch, lens thinner, weaker refraction
    • Cornea
      thick transparent layer which helps focus the light and protects it
    • Sclera
      Tough supporting wall of the eye
    • what is the retina made up of
      Receptor cells -
      • rod cells- more sensitive to light, only black and white
      • Cone cells- sensitive to Colour so we can see colour
    • fovea
      main spot on the retina which light focuses on to help us see clearly, has only cone cells
    • Myopia
      • short sightedness
      • light focusesed in front of the retina
      • Cause- eyeball is too long , lens is too curved
      • Solution - concave lens which spreads out the light so it focuses on retina
    • Hyperopia
      • longsightedness
      • Light is focused behind the retina
      • Causes - eyeball is too short and lens isn’t curved enough
      • Solution - convex lens which brings the light tgr so it focuses on retina
    • accomodation
      changing the shape of the lens to allow light to focus on the retina
    • Bright light
      Circular muscles contract, radial muscles relax, pupil gets smaller , less light goes through
    • Dim light
      Circular muscles relax, radial muscles contract, pupil gets bigger, more light is let through
    • Treatments for vision defects
      1. laser eye surgery, using a laser to change the shape of the cornea to refract light better, for short sighted people the cornea is shaved slimmer reducing the refraction, for long sighted ppl the cornea is made bigger to increase refraction
      2. Contact lenses- thin convenient lens that helps refract light, soft lens - comfortable , hard lens- risk of eye infections
      3. lens replacement- faulty lens is removed and replaced w an artificial one but high risk bcs Retina cld get damaged and patient can go blind
    • Blind spot
      Small area in the retina where no light is detected bcs there aren’t any rod or cone cells
    • Cataracts
      The lens becomes cloudy, blurry or reduced vision
      Treatment-lens replacement
    • describe how the brain revieves eye info
      cone cells in the retina detect light
      electrical impusle carried along a nueron
      in the optic nerve