Correcting vision defects

• Why are people long sighted

  The lens is the wrong shape and it doesn’t refract light enough

  or the eyeball is too short

  the images of near objects are brought into focus behind the retina
• hoe do you correct hyperopia

  glasses with a convex lens

  the lens refracts the light rays so they focus on the retina
• Why are people short sighted

  The lens is the wrong shape and refracts the light too much

  or the eyeball is to long

  the images of distant objects are brought into focus in front of the retina
• How do you correct myopia

  Glasses with a concave lens

  the light rays focus on the retina
• what do contact lenses do

  thin lenses that sit on the surface of the eye shaped to compensate for the fault in focusing
• why are contact lenses good

  lightweight, invisible better to wear for sports
• what’s the difference between hard lenses and soft lenses

  soft lenses are more comfortable but they carry a greater risk of infection
• how does laser eye surgery work

  A laser is used to vaporise tissue changing the shape of the cornea, changing how strongly it refracts light into the eye
• how does replacement lens surgery work

  the natural lens is removed and an artificial lens is put in its place

  higher risk than laser eye surgery because it involves work inside the eye