Correcting Vision Defects

• Long-sighted people are unable to focus on near objects:

  • This occurs when the lens is the wrong shape and doesn't refract the light enough or the eyeball is too short
  • The images of near objects are brought into focus behind the retina
  • You can use glasses with a convex lens to correct it. The lens refracts the light rays so they focus on the retina
  • The medical term for long-sightedness is hyperopia

  
• Short-sighted people are unable to focus on distant objects:

  • This occurs when the lens is the wrong shape and refracts the light too much or the eyeball is too long
  • The images of distant objects are brought into focus in front of the retina
  • You can use glasses with a concave lens (a lense which curves inwards) to correct it, so that the light rays focus on the retina
  • The medical term for short-sightedness is myopia

  
• Contact lenses:

  • Contact lenses are thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing
  • They're popular because they're lightweight and almost invisible
  • They're more convenient than glasses for activities like sports
• Contact lenses:

  • There are 2 main types of contact lenses are hard lenses and soft lenses
  • Soft lenses are are generally more comfortable, but carry higher risk of eye infections than hard lenses
• Laser eye surgery:

  • Bad eyesight can sometimes be corrected with laser eye surgery. A laser can be used to vaporise tissue, changing the shape of the cornea (and so changing how strongly it refracts light into the eye)
  • Slimming it down makes it less powerful and can improve short sight
  • Changing the shape so that it's more powerful will improve long sight
• Laser eye surgery:

  • The surgeon can precisely control how much tissue the laser takes off, completely correcting the vision
  • Like all surgical procedures, there is a risk of complications, such as infection or the eye reacting in a way that makes your vision worse than before
• Replacement lens surgery:

  • Sometimes hyperopia may be more effectively treated by replacing the lens of the eye (rather than changing the shape of the cornea with laser eye surgery)
  • In replacement lens surgery, the natural lens of the eye is removed and an artificial lens, made of clear plastic, is inserted in place
  • As it involves work inside the eye, replacing a lens carries higher risks than laser eye surgery, including possible damage to the retina (which could lead to a loss of sight)