Image Formation

  1. Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies.
    Minimum (top) and maximum accommodation (bottom)

    An example of shape constancy.


    Minimum (top) and maximum accommodation (bottom)

  2. The retina is the third and inner coat of the eye which is a light-sensitive layer of tissue.
  3. The fovea centralis is a small, central pit composed of closely packed cones in the eye. It is located in the center of the macula lutea of the retina.
  4. Visual acuity commonly refers to the clarity of vision. It is dependent on optical and neural factors.
    A typical Snellen chart. Originally developed by Dutch ophthalmologist Herman Snellen in 1862, to estimate visual acuity. When printed out at this size, the E on line one will be 88.7 mm (3.5 inches) tall and when viewed at a distance of 20 ft (= 609.6 centimeters, or 6.09600 meters), you can estimate your eyesight based on the smallest line you can read.

    The diagram shows the relative acuity of the left human eye (horizontal section) in degrees from the fovea.