The Eye

• The eye, a sense organ sensitive to light intensity and color, has structures like the retina, cornea, iris, ciliary muscles, suspensory ligaments, and lens adapted for focusing on near or distant objects
• The process of accommodation in the eye involves the ciliary muscles contracting to focus on near objects and relaxing to focus on distant objects
• Eye defects like myopia (short-sightedness) and hyperopia (long-sightedness) occur when light cannot focus properly on the retina
• Cataracts, clouding of the lens, and color blindness, the inability to see certain colors, are other eye defects that can be treated with methods like spectacle lenses, contact lenses, laser eye surgery, or replacement lens
• Contact lenes work by using a contact lens to apply a force to the cornea.
• Laser eye surgery works by using a laser to reshape the cornea to correct refractive errors.
• Replacement lens can treat eye defects such as hyperopia by replacing the lens with an artificial one made of clear plastic
• Label

  A) cornea

  B) iris

  C) pupil

  D) ciliary muscle

  E) lens

  F) sclera

  G) retina

  H) fovea

  I) optic nerve

  
• Label

  A) cornea

  B) Iris

  C) Lens

  D) Retina

  E) Optic nerve

  F) Sclera

  
• Explain why a short-sighted person has difficulty seeing distant objects clearly.

  Their eyeball is too long making the light focus in front of the retina, Resulting in an unclear image

  • Concave lens correct this by refracting the light and spreading it out focusing it onto the retina
• Explain why a long-sighted person has difficulty seeing distant objects clearly.

  Their eyeball is too short making the light focus behind the retina, Resulting in an unclear image

  • Convex lenses correct this by bending the light rays onto the retina
• To look at distant objects

  1. The Ciliary muscles relax, which allow the suspensory ligaments to pull tight
  2. This pulls the lens into a less rounded shape so light is refracted less
• To look at close objects

  1. The Ciliary muscles tighten, which slackens the suspensory ligaments
  2. The Lens becomes a more rounded shape, so light is refracted more