The Inner Workings of the Eye

Have you ever felt surprised what makes the human eye unique?

Human eyes have a widely exposed white sclera surrounding the darker coloured iris, making it easy to discern the direction in which they are looking. Humans have the largest ratio of exposed sclera in the eye outline, which itself is elongated horizontally. We suggest that these are adaptations to extend the visual field by allowing greater eye movement, especially in the horizontal direction, and to enhance the ease of detecting the gaze direction of another individual.

The eye interior

The eye receives oxygen through the aqueous. Its function is to nourish the cornea, iris, and lens by carrying nutrients, it removes waste products excreted from the lens, and maintain intraocular pressure and thus maintains the shape of the eye. This gives the eye its shape.

The main interior structures of your eyes include:

• The iris, which is the colored part of your eye.
• The pupil, the black circular opening in the center of the iris that lets in light.
• The crystalline lens, suspended behind the iris, which allows you to focus on near and far objects.
• The retina, which is a very thin layer of millions of photoreceptors called "rods and cones.

Anatomy that  Involved in Creating the Images that go to the Brain

• Cornea: the clear layer at the very front of the eye that allows light inside.

• Iris: the colorful, circular muscle that contracts and expands to control the amount of light entering the eye.
• Lens: a clear disc that changes shape in order to focus on objects at different distances. (This is different from the lens in a camera, which is rigid and must physically move in order to change focus.)
• Retina: a thin layer of tissue at the back of the eye covered in light-sensitive cells called rods and cones.
• Optic nerve: the nerve that transmits visual information from the retina to the brain for processing at an estimated rate of around a million bits per second.
• Conjunctiva:The surface of the eye and of the inner eyelids is covered by a clear, protective membrane called the “conjunctiva.”The conjunctiva is lubricated by several substances produced by the body to keep the eye in good working order. These substances, which include mucous, oils, and a watery solution, prevent the eye from drying out and protect it from surface irritants.
• Anterior chamber:The anterior chamber of the eye refers to a small pocket of fluid that lies between the cornea and the iris. This fluid is “aqueous humor” a watery solution that helps the cornea and pupil to focus light.
• Posterior chamber:The posterior chamber refers to the aqueous fluid-filled chamber behind the iris and pupil. The posterior chamber sits between the iris and the lens, which completes the job of focusing light.
• Pupil:The pupil is the opening to the inner chamber of the eye. Pupils appear black because light passes through them and does not return. The pupil, then, is our actual “window to the world.”
• Vitreous humor:The vitreous humor is a thick, gelatinous fluid that fills most of the eyeball. Like the aqueous humor, it refracts light at a constant rate – but unlike the aqueous humor, it is thick and jelly-like.

• Sclera:The sclera is also known as the “white of the eye.” It is – as you may have guessed the white part of the eye that surrounds the iris and pupil.The sclera does not collect visual data itself. Instead it acts as a tough, protective membrane for the eyeball.