Vision and the Eye

Dominance of Vision

• Vision is the primary sense for most people with sight.
• The organ responsible for vision is the eye, which is a slightly irregular, hollow sphere.

Structure of the Eye

• Cornea: A clear, dome-like structure covering the iris (colored part of the eye).
• Lens: Located directly below the cornea.
• Retina: Lines the back of the eye, consisting of light-sensitive tissue layers.

Image Formation Process

1. Light Passage:
   • Light enters through the cornea and is refracted onto the lens.
   • The lens bends the light a second time.
2. Image at the Retina:
   • The double bending process forms an upside-down image on the retina.
3. Brain Correction:
   • Image travels as impulses along the optic nerve to the occipital lobe of the brain.
   • The brain adjusts the image to its correct, upright perspective.

Common Vision Conditions

Nearsightedness (Myopia)

• Occurs when the eye is longer than normal.
• Focal point falls in front of the retina.
• Difficulty seeing distant objects.
• Correction: Concave lenses in glasses push the focal point onto the retina.

Farsightedness (Hyperopia)

• Occurs when the eye is shorter than normal.
• Focal point is behind the retina.
• Difficulty seeing close objects.
• Correction: Convex lenses in glasses move the focal point onto the retina.