Vision

• What regulates the amount of light entering the eye?

  Iris
• What type of image is formed on the retina?

  Real and inverted
• How does the human eye focus an image on the retina?

  By varying the convexity of the eye lens
• What causes the change in focal length of the eye lens?

  Ciliary muscle
• Which color is least scattered by dust and fog?

  Red
• What is the process of vision?

  • Eyes and brain work together
  • Perceive and interpret light
  • Enables understanding of surroundings
  • Involves eye, optic nerves, and brain
• What is the function of the sclera?

  • Tough outer layer of eyeball
  • Covers posterior five-sixths of eye
  • Provides protection for eyeball contents
• What is the choroid's role in the eye?

  • Thin vascular layer between sclera and retina
  • Provides nourishment to eyeball structures
  • Contains many blood vessels
• What are the functions of the cornea?

  • Transparent convex anterior portion
  • Sensitive to pain, touch, pressure, and cold
  • Contributes to refractive power of the eye
• What does the conjunctiva do?

  • Covers exposed part of the eye
  • Protects eye by sealing it in the socket
  • Lubricated by a thin film of tears
• What is the ciliary body's structure and function?

  • Consists of ciliary muscles and processes
  • Muscles help in accommodation
  • Processes secrete aqueous humor
• What is the iris and its functions?

  • Central aperture called pupil
  • Controls light intensity entering the eye
  • Protects from bright light
• What are the characteristics of the lens?

  • Biconvex, transparent, and elastic
  • Avascular, receives nutrition from aqueous humor
  • Plays a major role in accommodation
• What is the focal length of the human lens?

  $44 \text{ mm}$
• What is the refractive power of the lens?

  $23 \text{ D}$
• What is the function of aqueous humor?

  • Maintains shape of eyeball
  • Maintains intraocular pressure (15-18 mm/Hg)
  • Provides nutrients to avascular structures
• What is vitreous humor and its functions?

  • Viscous fluid behind lens
  • Maintains shape of eyeball
  • Protects eyeball internally
• What is accommodation in the eye?

  • Adjustment to see near or distant objects
  • Involves changes in lens curvature
  • Achieved by ciliary muscle adjustments
• What is dark adaptation?

  • Ability to see in dim light
  • Increased sensitivity of rods
  • Pupil dilatation allows more light
• What is light adaptation?

  • Adjustment to increased illumination
  • Reduced sensitivity of rods
  • Pupil constriction reduces light entry
• What are primary colors of light?

  • Red, green, and blue
  • Combine to produce white light
• What are complementary colors?

  • Pairs that produce white when mixed
  • Example: Red and blue make purple
• What is night blindness?

  • Loss of vision in dim light
  • Caused by vitamin A deficiency
  • Affects rod function and retinal layers
• What is the other name for night blindness?

  Nyctalopia
• What happens during prolonged vitamin A deficiency?

  • Leads to anatomical changes in rods and cones
  • Causes degeneration of retinal layers