ABOUT Cornea

The cornea is the transparent part of the eye that covers the front portion of the eye. It covers the pupil (the opening at the center of the eye), iris (the colored part of the eye), and anterior chamber (the fluid-filled inside of the eye). The cornea's main function is to refract, or bend, light. The cornea is responsible for focusing most of the light that enters the eye.

Human body Nervous SystemBrainCornea Cornea The cornea is the transparent part of the eye that covers the front portion of the eye. It covers the pupil (the opening at the center of the eye), iris (the colored part of the eye), and anterior chamber (the fluid-filled inside of the eye). The cornea's main function is to refract, or bend, light. The cornea is responsible for focusing most of the light that enters the eye. The cornea is composed of proteins and cells. It does not contain blood vessels, unlike most of the tissues in the human body. Blood vessels may cloud the cornea, which may prevent it from refracting light properly and may adversely affect vision.

Cornea

Cornea effects

The cornea has five layers. From front to back, these layers are:

This outer layer of the cornea is five to seven cells thick and measures about 50 microns — making it slightly less than 10 percent of the thickness of the entire cornea. Epithelial cells are constantly being produced and sloughed off in the tear layer of the surface of the eye. The turnover time for the entire corneal epithelium is about one week.

This is a very thin (8 to 14 microns) and dense fibrous sheet of connective tissue that forms the transition between the corneal epithelium and the underlying stroma.The dense nature of Bowman's layer helps prevent corneal scratches from penetrating into the corneal stroma. Corneal abrasions that are limited to the outer epithelial layer generally heal without scarring; but scratches that penetrate Bowman's layer and the corneal stroma typically leave permanent scars that can affect vision.

This middle layer of the cornea is approximately 500 microns thick, or about 90 percent of the thickness of the overall cornea. It is composed of strands of connective tissue called collagen fibrils. These fibrils are uniform in size and are arranged parallel to the cornea surface in 200 to 300 flat bundles called lamellae that extend across the entire cornea. The regular arrangement and uniform spacing of these lamellae is what enables the cornea to be perfectly clear.

This very thin layer separates the stroma from the underlying endothelial layer of the cornea. Descemet's (pronounced "DESS-eh-mays") membrane gradually thickens throughout life — it's about 5 microns thick in children and 15 microns thick in older adults.

This is the innermost layer of the cornea. The back of the endothelium is bathed in the clear aqueous humor that fills the space between the cornea and the iris and pupil. The corneal endothelium is only a single layer of cells thick and measures about 5 microns. Most of the endothelial cells are hexagonal (six-sided), but some may have five or seven sides. The regular arrangement of these cells is sometimes called the endothelial mosaic.

What are corneal dystrophies

Keratoconus

Keratoconus causes the middle of the cornea to thin, bulge outward, and form a rounded cone shape. This abnormal curvature of the cornea can cause double or blurred vision, nearsightedness, astigmatism, and increased sensitivity to light

Fuchs’ Dystrophy

It is a slowly progressing disease that usually affects both eyes and is slightly more common in women than in men. It can cause your vision to gradually worsen over many years, but most people with Fuchs’ dystrophy won’t notice vision problems until they reach their 50s or 60s.

Lattice Dystrophy

It gets its name from a characteristic lattice-like pattern of deposits in the stroma layer of the cornea. The deposits are made of amyloid, an abnormal protein fiber. Over time, the deposits increase and the lattice lines grow opaque.

Map-­Dot­-Fingerprint Dystrophy

It occurs when the basement membrane develops abnormally and forms folds in the tissue. The folds create gray shapes that look like continents on a map.

What are some common conditions that affect the cornea?

Injuries

Injuries

After minor injuries or scratches, the cornea usually heals on its own. Deeper injuries can cause corneal scarring, resulting in a haze on the cornea that impairs vision. If you have a deep injury, or a corneal disease or disorder

Allergies

Allergies

The most common allergies that affect the eye are those related to pollen, particularly when the weather is warm and dry. Symptoms in the eye include redness, itching, tearing, burning, stinging, and watery discharge, although usually not severe enough to require medical attention.

Keratitis

Keratitis

Keratitis is an inflammation of the cornea. Noninfectious keratitis can be caused by a minor injury, or from wearing contact lenses too long. Infection is the most common cause of keratitis. Infectious keratitis can be caused by bacteria, viruses, fungi or parasites.

Dry eye

Dry eye

Dry eye is a condition in which the eye produces fewer or lower quality tears and is unable to keep its surface lubricated. The main symptom of dry eye is usually a scratchy feeling or as if something is in your eye. Other symptoms include stinging or burning in the eye.

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