Eye anatomy. Photo © A.D.A.M.

The eye is an organ that detects light and sends signals along the optic nerve to the brain. In humans, the eye is a valuable sense organ that gives us the ability to see. It allows for light perception and vision, including the ability to differentiate between colors and depth.

Although small in size, the eye is a very complex organ. The eye is approximately 1 inch wide, 1 inch deep and 0.9 inches tall.

The human eye has a 200-degree viewing angle and can see 10 million colors and shades. Humans have two eyes which allows us to have better depth perception and binocular stereopsis. 

Anatomy of the Eye

  • Cornea - The cornea is the clear, dome-like structure on the front part of the eye.The cornea delivers 2/3 of the refracting power to the eye.
  • Conjunctiva - The conjunctiva is a mucus membrane that covers the surface of the eye and the inner part of the eyelids.
  • Sclera - The sclera is the white, tough, outer covering of globe of the eye. The sclera is continuous with the cornea.
  • Iris - The iris is a pigmented tissue with two muscles that control pupil constriction and pupil dilation. The iris acts like a diaphragm that controls the amount of light allowed into the eye. The iris is the colored part of the eye. 
  • Pupil - The pupil is the hole in the middle of the iris in which light pass through to the retina. The pupil is black because the light that is allowed into the eye is absorbed in the retina.
  • Anterior Chamber - The anterior chamber is the fluid-filled chamber between the iris and the cornea's inner surface which is comprised of the endothelium. Aqueous humor is the fluid that fills the anterior chamber
  • Trabecular meshwork - The trabecular meshwork is a meshwork of tissue located around the base of the cornea, in the angle of the eye. The trabecular meshwork is continuous with the ciliary body. It is responsible for draining the aqueous humor into a Schlemm's canal (drainage tubes) and into the blood system.
  • Crystalline Lens - The Crystalline lens delivers 1/3 of the refracting or focusing power to the eye.  It is a fibrous tissue that can change shape to increase or decrease its power. Because it can change shape, it allows the eye to focus on intermediate and near objects. 
  • Ciliary body - The Crystalline lens is attached to the ciliary body by lens zonules. The ciliary body is a muscle that can contract to change the shape of the lens. This allows humans to carefully focus on near objects. The other function of the ciliary body is to produce aqueous humor that flows into the anterior chamber.
  • Retina - The retina is a light sensitive tissue that captures light energy and transfers that energy to the brain as nerve impulses 
  • Optic nerve - The optic nerve is a network of nerve cells which receives impulses from the nerve fiber layer on the retina. It transfers nerve impulses to the brain. 

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