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How does the eye perceive light?

When light enters the eye, it passes through the cornea first and ultimately reaches the retina (the light-sensing structure of the eye). Two types of cells are located in the retina - rods and cones. Rods control vision in low light; cones handle color vision and detail. When light comes in contact with these two types of cells, a series of chemical reactions occur.

The formed chemical (called activated rhodopsin) creates electrical impulses in the optic nerve.

Activated rhodopsin affects those electrical impulses in the following way:

  • 1. The outer layer of a rod cell has an electric charge. Light activates rhodopsin, which causes a reduction in cyclic GMP. This makes the electric charge increase. The increased electric charge produces an electric current along the cell. As more light is detected, more rhodopsin is activated and, therefore, more electric current is produced.
  • 2. The electric impulse eventually reaches a ganglion cell, followed by the optic nerve.
  • 3. The nerves reach the optic chasm. Here, nerve fibers from the inside half of each retina will cross to the other side of the brain. The nerve fibers from the outside half of the retina, however, stay on the same side of the brain.
  • 4. The fibers eventually reach the back of the brain. Here, at the primary visual cortex, is where vision is interpreted. Some visual fibers go to other parts of the brain and help to control eye movements, pupil and iris response, and behavior.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.