What Is Cornea?
The cornea is the dark, transparent, circular part of the front of the eyes. It is the only transparent structure of the human body and is the main determinant of the crystal-clear vision that people have come to expect from the eyes. Just like how the cornea, being a clear lens, enables individuals to see the world around them, the cornea is also a boon to doctors who can visualize the internal structures of the eye and blood vessels by directly viewing through the cornea without even having to touch the patient. This remarkable ability of the cornea to maintain its own transparency is made possible by a delicate balance of water and the intracorneal pressure and hydrostatic forces that preserve this state of transparency.
Just as bad are the visual results when this delicate balance is lost by disease or otherwise, where the patient's vision may go down in a matter of minutes from being able to read the fine print to just being able to detect the presence of light. Thus, the role of the cornea in visual capacity is unmatched and irreplaceable. Like any other part of the body, the cornea also has its own host of very fulminant diseases, which, as mentioned before, hamper the vision by disrupting this delicate balance within the cornea. This article throws some light on common corneal disorders and ways to prevent them.
What Is the Main Reason for Cornea’s Transparency?
The main reasons for the transparency of the cornea are:
1. The State of Relative Dehydration:
The normal water content of the human body is around 66 percent, but the corneal water content is around 82 percent. This being said, the cornea is still said to be relatively dehydrated. This is because the water is kept at a very strict level of control by special cells called endothelial cells, which pump water out of the cornea at a constant rate. This enables the cornea to be in a constantly dehydrated state, even if the overall content is more than the rest of the body.
Whenever there is a breach in the corneal barriers, this gives way for water to flood into the cornea and hamper vision. The best and most common example is a corneal ulcer, where a wound over the cornea can cause inflammation and fluid to enter into the cornea. This is usually seen as a cloudy or white area on the normally clear and transparent cornea.
2. The Cornea Has No Blood Vessels or Lymphatic Vessels:
The absence of blood vessels is a remarkable adaptation that enables clear vision. Conditions such as contact lens wear, corneal graft, or interstitial keratitis can cause the growth of blood vessels onto the cornea and disrupt the corneal clarity.
3. The Orientation of Fibers of the Cornea Is Very Precise:
The fibers in the cornea are masterfully crafted and oriented such that whatever light rays get scattered after falling on them destroy each other and get nullified by a process called destructive interference. This process causes the cornea to scatter very little light and hence improves vision. The arrangement of fibers is also such that the gap between any two of the corneal fibers is less than the wavelength of visible light, once again contributing to corneal clarity. Under normal circumstances, the above mechanisms work like clockwork, keeping the cornea crystal clear.
What Are the Common Corneal Disorders?
The under-mentioned are the most common causes affecting the cornea by hampering this mechanism and causing blindness.
1. Corneal Ulcer - A corneal ulcer usually indicates a grave problem and is considered an ocular emergency. The problem is made worse by the fact that there are no blood vessels in the cornea to facilitate the healing of the wound.
An ulcer can be caused by a variety of causative factors such as direct trauma, the flash of very bright objects such as an electric arc, certain chemical fumes, infection with organisms (adenovirus, cocci, bacilli, Acanthamoeba, fungi), and autoimmune disorders (Mooren's ulcer).
The most common of the causes are either direct trauma or contact lenses. Contact lenses act by cutting out the oxygen supply to the corneal cells and killing cells due to lack of oxygen. Like any other injury, the ulcer causes a breach in the corneal barriers and allows flooding of water into the cornea. This hampers vision and causes pain.
2. Corneal Edema - It is usually caused by the failure of the endothelial pump mechanism and is common in the elderly after the age of 50. Women are more prone to corneal edema than men. Apart from aging, contact lenses, eye surgery, medications, and herpes infections can also lead to corneal edema. Such people experience irritation in the eye, a halo around lights, and pain upon touching the eye or viewing bright lights.
3. Corneal Opacity - It is the end result of corneal disease and represents a scarred and opaque cornea. Eye injury, measles, herpes simplex viral infection, using contact lenses even at night during sleep, vitamin A deficiencies, and eye infections like conjunctivitis can cause corneal opacity.
What Are the Additional Ailments That May Impact the Cornea?
Other ailments that affect the cornea include:
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Bullous Keratopathy: Surface blisters and edema of the cornea. This could occur as a result of corneal dystrophy or following eye surgery. The symptoms, which include light sensitivity and hazy vision, are typically most severe in the morning.
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Corneal Abrasion: An exposed cut on the cornea's surface is called a corneal abrasion. It frequently results in watering, eye discomfort, and impaired vision. Although it can sometimes happen with severe dry eye illness, it usually happens following trauma, such as a scrape on the nail.
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Herpes Eye Disease: A painful illness resulting from an eye infection by the herpes virus.
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Iridocorneal Endothelial Syndrome (ICE): Rarely, corneal edema and elevated intraocular pressure are symptoms of the iridocorneal endothelial syndrome (ICE).
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Pterygium: An amorphous protrusion on the white portion of the eye that may occasionally cause scarring and spread to the cornea.
What Are the Measures to Avoid Corneal Disease?
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No matter how small the eye infection is, always get an ophthalmologist’s opinion. The most benign of eye problems, like conjunctivitis, unless treated well, can form ulcers.
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Never use contact lenses regularly and beyond the prescribed limits of the duration of use. Also, do not use contact lenses at night during sleep.
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If there are any injuries to the eye, kindly get an ophthalmologist’s appointment right away.
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For people whose work involves traveling in dust or welders and grinding operators, always wear safety glasses.
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Do not rub the injured or scratchy eye.
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If individuals suspect any foreign material within their eyes, they can rinse it with fresh and clean water.
Who Is Susceptible to Corneal Diseases?
Certain corneal diseases, such as corneal dystrophies, are inherited. However, there are things one may do to lessen the chance of getting infections and corneal damage.
Use safety glasses to avoid corneal damage while individuals:
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Play ball or puck sports, such as hockey or baseball.
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Perform yard chores, such as weed whacking or grass mowing.
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Make repairs by pounding or painting.
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Use tools such as drills and sanders.
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Apply chemicals, such as insecticides or bleach.
How Can Corneal Disorders Be Treated?
Prescription eye drops or tablets can be used to treat a variety of corneal problems. Some other treatment options for advanced conditions are as follows:
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Laser Therapy: Phototherapeutic keratectomy (PTK) is a form of laser treatment that doctors can use to manage some corneal dystrophies and other disorders. PTK helps eliminate scar tissue from the cornea, restructure it, and enhance eyesight.
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Procedure for Corneal Transplants: In cases when corneal restoration is not feasible, medical professionals may opt to replace the affected area with donor corneal tissue that is in good condition.
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Artificial Cornea: Doctors can use keratoprosthesis (KPro), an artificial cornea, to repair a damaged cornea instead of doing a corneal transplant.
Conclusion:
A variety of illnesses that affect the cornea are grouped as corneal disorders. It is crucial to keep in mind that several therapies are available to help preserve vision and improve the eyes' health, even if certain problems might seem frightening. One can reduce the risk of corneal injury by wearing safety glasses while doing activities like live mowing, drilling, etc. If one experiences any change in the vision, consult a physician to determine the cause and suitable treatment method.
