How the eye focuses (accommodation)

• What is the role of the retina in the eye?

  It contains receptor cells sensitive to light
• What part of the eye carries out most of the focusing?

  The cornea
• What is accommodation in the context of the eye?

  The ability to change lens shape for focus
• How does the ciliary muscle affect the lens during accommodation?

  It changes the thickness of the lens
• What happens when the ciliary muscle contracts?

  The lens becomes thicker and refracts light more
• What occurs when the ciliary muscle relaxes?

  The lens becomes thinner and refracts light less
• What is the key fact about focusing on distant objects?

  Light needs to be focused only a small amount
• How does the eye focus on near objects?

  The ciliary muscle contracts, thickening the lens
• What is long-sightedness also called?

  Hyperopia
• What problem do people with long-sightedness face?

  They cannot focus on nearby objects
• Why do some people experience long-sightedness?

  The eyeball may be too short
• How can long-sightedness be treated?

  Using glasses with convex lenses
• What is short-sightedness also called?

  Myopia
• What issue do people with short-sightedness have?

  They cannot focus on distant objects
• What causes short-sightedness in some individuals?

  The eyeball may be too long
• How can short-sightedness be treated?

  Using glasses with concave lenses
• What alternative to glasses can be used for vision correction?

  Contact lenses
• What is one recent treatment for long and short-sightedness?

  Laser surgery to change cornea shape
• What can sometimes be replaced to treat vision issues?

  The lenses inside the eye
• What are the steps involved in accommodation for focusing on near and distant objects?

  • For distant objects:
  • Ciliary muscle relaxes
  • Suspensory ligaments tighten
  • Lens becomes thin
  • Light is slightly refracted
  • For near objects:
  • Ciliary muscle contracts
  • Suspensory ligaments loosen
  • Lens becomes thick
  • Light is strongly refracted
• What are the characteristics of long-sightedness and short-sightedness?

  • Long-sightedness (Hyperopia):
  • Can focus on distant objects
  • Cannot focus on nearby objects
  • Eyeball may be too short
  • Treated with convex lenses
  • Short-sightedness (Myopia):
  • Can focus on nearby objects
  • Cannot focus on distant objects
  • Eyeball may be too long
  • Treated with concave lenses
• What are the treatment options for vision correction?

  • Glasses (convex for long-sightedness, concave for short-sightedness)
  • Contact lenses (hard or soft)
  • Laser surgery to reshape cornea
  • Replacement of lenses inside the eye
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  Distance .

  
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  Up close

  
• Long sight

  
• Short sight

  
• 


  Eye in different sources of light