Human eyeball

From WikiMD's Wellness Encyclopedia

Human eyeball
   200px
Cross-sectional view of the human eyeball
Latin bulbus oculi
Nerve Optic nerve
System Visual system


The human eyeball is a complex organ responsible for vision, allowing humans to perceive and interpret their surroundings. It is a roughly spherical structure located in the orbit of the skull, protected by the eyelids and cushioned by orbital fat.

Anatomy[edit | edit source]

The human eyeball is composed of three main layers:

Outer Layer[edit | edit source]

The outermost layer consists of the sclera and the cornea.

  • Sclera: The sclera is the white, opaque part of the eye that provides protection and form. It is continuous with the cornea at the front of the eye.
  • Cornea: The cornea is the transparent, dome-shaped surface that covers the front of the eye. It plays a crucial role in focusing light onto the retina.

Middle Layer[edit | edit source]

The middle layer, also known as the uvea, includes the choroid, ciliary body, and iris.

  • Choroid: The choroid is a vascular layer that supplies blood to the retina and other parts of the eye.
  • Ciliary Body: The ciliary body contains the ciliary muscle, which controls the shape of the lens, and the ciliary processes, which produce aqueous humor.
  • Iris: The iris is the colored part of the eye that controls the size of the pupil, regulating the amount of light entering the eye.

Inner Layer[edit | edit source]

The innermost layer is the retina, which contains photoreceptor cells.

  • Retina: The retina is a light-sensitive layer that converts light into neural signals. It contains two types of photoreceptor cells: rod cells and cone cells.

Internal Structures[edit | edit source]

  • Lens: The lens is a transparent, flexible structure that focuses light onto the retina. It is held in place by the zonule of Zinn.
  • Vitreous Body: The vitreous body is a clear gel that fills the space between the lens and the retina, helping maintain the eyeball's shape.

Function[edit | edit source]

The primary function of the human eyeball is to capture light and convert it into electrical signals that can be interpreted by the brain. This process involves several steps:

1. Light enters the eye through the cornea and passes through the pupil. 2. The lens focuses the light onto the retina. 3. Photoreceptor cells in the retina convert the light into electrical signals. 4. These signals are transmitted to the brain via the optic nerve.

Clinical Significance[edit | edit source]

The human eyeball can be affected by various conditions, including:

  • Cataract: Clouding of the lens, leading to decreased vision.
  • Glaucoma: A group of eye conditions that damage the optic nerve, often due to high intraocular pressure.
  • Macular degeneration: A disease that affects the central part of the retina, leading to vision loss.

Also see[edit | edit source]

Template:Anatomy of the human eye

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Contributors: Prab R. Tumpati, MD