Human eyeball

General Information
Latin	bulbus oculi
Greek
TA98
TA2
FMA
Details
System	Visual system
Artery	Ophthalmic artery
Vein	Ophthalmic vein
Nerve	Optic nerve
Lymphatic drainage
Precursor
Function
Identifiers
Clinical significance
Notes

The human eyeball is a complex organ responsible for vision, allowing humans to perceive the world around them. It is part of the visual system and is located in the orbit of the skull.

Anatomy

The human eyeball is approximately 24 mm in diameter and consists of three main layers:

• The outer layer, known as the sclera, is a tough, protective coating that maintains the shape of the eye. The front part of the sclera is the cornea, which is transparent and allows light to enter the eye.

• The middle layer, called the uvea, includes the choroid, ciliary body, and iris. The choroid contains blood vessels that supply nutrients to the eye, while the ciliary body controls the shape of the lens. The iris is the colored part of the eye that regulates the size of the pupil, controlling the amount of light that enters the eye.

• The innermost layer is the retina, which contains photoreceptor cells that detect light and convert it into electrical signals. These signals are transmitted to the brain via the optic nerve.

Function

The primary function of the human eyeball is to focus light onto the retina, where it is converted into neural signals. This process involves several key components:

• The cornea and lens work together to refract light, focusing it onto the retina.
• The pupil adjusts its size to control the amount of light entering the eye.
• The retina contains two types of photoreceptor cells: rods and cones. Rods are responsible for vision in low light conditions, while cones are responsible for color vision and detail.

Common Disorders

Several disorders can affect the human eyeball, impacting vision:

• Myopia (nearsightedness) occurs when the eyeball is too long, causing light to focus in front of the retina.
• Hyperopia (farsightedness) occurs when the eyeball is too short, causing light to focus behind the retina.
• Astigmatism is caused by an irregular curvature of the cornea or lens, leading to blurred vision.
• Cataracts are a clouding of the lens, leading to decreased vision.
• Glaucoma is a group of diseases that damage the optic nerve, often due to increased pressure in the eye.

See Also

• Visual acuity
• Color vision
• Eye care professional

References

• Anatomy of the Eye - American Academy of Ophthalmology
• Eye Conditions and Diseases - National Eye Institute