AP Psychology - The Eye

Cornea

• Eye’s clear, protective outer layer covering the pupil and iris

  • Light enters the eye through this part first

Pupil

• A small adjustable opening in the center of the eye through which light passes

Iris

• A ring of muscle tissue that forms the colored portion of the eye around the pupil

• Controls the size of the pupil opening by expanding and contracting over the pupil

Lens

• The transparent structure behind the pupil that changes shape to help focus images on the retina

  • Accommodation: The action of changing its curvature and thickness to focus light rays

• If image focused in front of the retina, you have myopia (nearsightedness)

• If image focused past the retina, you have hyperopia (farsightedness)

Retina

• The light-sensitive inner surface of the eye, containing the receptor rods and cones with a layer of neurons that begin the processing of visual information

Rods

• Retinal photoreceptors that detect black, white, and gray, and are sensitive to movement

  • Necessary for peripheral and twilight vision, when cones don’t respond

• Characteristics of rods

  • Located along the retina’s outer periphery

  • Remain sensitive in dim light → enable black-and-white vision

  • Have no hotline to the brain → share connections to a single bipolar cell sending a combined message to the brain

  • Are sensitive to faint light and peripheral motion

Cones

• Retinal photoreceptors that are concentrated near the center of the retina and function in daylight or in well-lit conditions

  • Detect fine detail and create color sensations

• Characteristics of cones

  • Cones cluster in and around the fovea

  • Become unresponsive in dim light → become unable to see color

  • Many have their own hotline to the brain → one cone transmits its message to a single bipolar cell, which relays the message to the visual cortex

Fovea

• The central focal point in the retina, around which the eye’s cones cluster

• The area of greatest visual acuity or sharpness of focus

Optic Nerve

• Comprised of the axons of the ganglion cells

• Leaves through the back of the eye and carries the neural impulses from the eye to the brain

Blind Spot/Optic Disk

• The point at which the optic nerve leaves the eye

• No receptor cells (rods or cones) are located there