Vision and Color Blindness Notes

Vision Defects

Myopia

• Myopia, also known as nearsightedness, is a refractive error where distant objects appear blurry while close objects are seen clearly.

Hyperopia

• Hyperopia, also known as farsightedness, is a refractive error where close objects appear blurry while distant objects are seen clearly.

Astigmatism

• Astigmatism is a refractive error where the eye cannot focus light rays that enter on different planes simultaneously.
• It is corrected with a cylindrical lens.

Color Blindness

• Color blindness is typically a hereditary condition resulting from a lack of a specific pigment (photopsin) in the eye.
• This pigment deficiency prevents a person from perceiving certain color differences.
• Individuals with mild color blindness might not realize they have the condition until tested.
• Red-green color blindness is the most prevalent type.
• In red-green color blindness, the red cones may respond to green light, or vice versa.

Cone Types and Light Absorption

• There are three major cone types in the eye, each sensitive to a primary color of light: red, green, and blue.
• Each cone type is most effectively stimulated by its corresponding color.
• In the absence of properly functioning cones, other cones may be inappropriately stimulated.

Red-Green Color Blindness Details

• Red-green color blindness occurs when red cones respond to green light or vice versa.
• Patients with this condition have missing or damaged red or green cones that cannot respond appropriately to colored light.
• As a result, they are incapable of distinguishing red from green.
• Red-green color blindness is a sex-linked recessive trait, affecting approximately 8% of males and 0.5% of females.

Wavelength and Absorption

• The X-axis on the provided graph represents the wavelength of light corresponding to color, ranging from 400nm to 750nm.
• The Y-axis represents absorption, indicating that cones with high absorption at a particular wavelength easily detect that color.
• Different types of cones and rods have different absorption peaks:
  • Rods peak at approximately 498nm.
  • Short cones peak at approximately 420nm.
  • Medium cones peak at approximately 534nm.
  • Long cones peak at approximately 564nm.