Around 3 percent of all visits to the emergency department in the United States are as a result of eye trauma. And, the vast majority of these visits involve some kind of injury to the cornea.
Corneal injuries can vary greatly in seriousness, from insignificant and minor to those which may even result in permanent loss of vision. Injuries to the cornea are usually related to either trauma, such as a corneal abrasion, or exposure, such as burns from chemical sources.
Here we take a closer look at the cornea and explain the most common signs of injury.
What Is the Cornea?
The cornea is the clear, protective outer layer of the eye. Alongside the sclera (the white part of your eye), the cornea is a barrier against germs, dirt and other things that may cause damage.
Your cornea can also filter out some of ultraviolet (UV) light emitted by the sun. But, it’s not effective enough to block out much of this UV light. So, it is recommended you wear sunglasses outdoors to keep your corneas healthy.
The cornea also plays an important role in vision. As light enters your eye, it is refracted by the cornea’s dome-shaped surface. This then determines how well your eye can focus on objects in the distance and close-up.
The Structure of the Cornea
To understand the potential problems of cornea injuries, it helps to know how the cornea is structured. Although the cornea is clear and appears to lack substance, it is a complex and organized tissue.
In contrast to most tissues in the body, the cornea doesn’t contain any blood vessels to protect itself against infection or provide nourishment. Instead, the cornea gets its nourishment from tears and from the aqueous humor, which is fluid in the front of the eye just behind the cornea.
The individual tissues of the cornea are arranged into several layers and membranes, all with distinct and important functions:
The epithelium is the outermost layer of the cornea. Its main functions are to:
- Block foreign material, such as water, dust, and bacteria from entering the eye
- Provide a smooth surface to absorb nutrients and oxygen from tears, and to then distribute these among the other layers of the cornea
The epithelium has thousands of tiny nerve endings. This is why your eye may hurt when you rub or scratch it.
Between the epithelium and the next layer of the cornea is the basement membrane. Epithelial cells anchor themselves to this layer to form the connection between one layer and another.
Behind the basement membrane, you will find a transparent film of tissue called Bowman’s layer. This is composed of protein fibers, also known as collagen.
If the Bowman’s layer is injured, it can form a scar as it heals. And, if these scars are centrally located and large enough, they can cause vision loss.
Behind Bowman’s layer is the stroma. The stroma is the thickest layer of the cornea and is mainly made of water and collagen. This collagen gives the cornea its elasticity, form, and strength.
The unique way that the collagen proteins are spaced, shaped and arranged within the stroma is essential for the cornea’s light-conducting transparency.
Descemet’s membrane is a thin but very strong film of tissue located behind the stroma. This membrane serves as a protective barrier against injury and infection, and it is highly effective at repairing itself after injury.
Like the stroma, Descemet’s membrane is composed of collagen fibers, but these fibers are different from those of the stroma. The collagen fibers in Descemet’s membrane are made by cells in the endothelial layer of the cornea, located behind this membrane.
Behind the other layers of the eye, you will find the endothelium, the innermost layer of the cornea.
Endothelial cells play an important role in keeping the cornea clear. As a rule, fluid leaks slowly into the stroma from inside the eye. The endothelium’s main task is to pump this excess liquid out of the stroma.
A healthy eye works to maintain a perfect balance between the fluid moving into and out of the cornea. Without this pumping action, the stroma would overload with water, resulting in it swelling to become thick and opaque.
But, unlike the cells in Descemet’s membrane, endothelial cells which have been damaged or destroyed are not repaired or replaced by the body.
10 Signs of Corneal Injury
As your eye’s first defense against foreign bodies, scratches, and other injuries, it is important to treat injuries to the cornea seriously. If your cornea is damaged by injury, the resulting scars can affect your vision. This is because the scars can distort or block light as it enters your eye.
Your cornea is usually able to heal itself after most minor injuries. But, during the healing process, you may notice the following symptoms:
As explained above, the epithelium is filled with thousands of tiny nerve endings, meaning you will feel pain when you rub or scratch your eye. Under normal circumstances, this pain serves as a warning to avoid touching your eyes. And, due to the sensitivity of your eyes, it is always a good idea to wear protective goggles in hazardous environments.
If you’ve scratched your eye, this pain is a sign that you may have damaged your cornea. The severity of the pain depends on the extent of the injury. In most cases, a scratched eye due to a fingernail or a small piece of sand or dust will result in mild to medium pain or discomfort.
But, pain from injury to the cornea can sometimes be delayed for several hours after the event. As such, you may not always be aware of the cause of the injury. If the pain continues or becomes worse over time, you should seek medical treatment.
- Dry Eyes
While dry eyes is also an eye condition in itself, it can be a sign of a scratched cornea. This is because corneal abrasion can cause a delayed reaction or changes to normal tear production.
- Excess Tears
As a result of injury to the cornea, you may also experience excess tearing.
This is often the body’s reaction to the injury, whereby it produces more tears than usual to help overcome the injury and clean the surface of the cornea. Also, if the injury is caused by a foreign object in the eye such as a piece of sand or dust, this can help flush out the object.
- Sensation of a Foreign Object in the Eye
Injury to the cornea can also cause a gritty sensation which feels like you have something in your eye. This feeling is often made worse when you blink or move your eyeball around.
Injuries that are the result of a foreign body, such as dirt or dust in the eye will cause this sensation. But, even if you don’t have something in your eye, the resulting injury or scratch may still feel as if something is there.
Eye redness can be caused by rubbing the injured eye. It’s common for people to rub their eyes when they experience the sensation of a foreign object or irritation to the eye. But, you should avoid rubbing as this can make matters worse.
Injury to the cornea can also cause discharge or mucus in the eye. This eye discharge has a protective function, serving to remove waste products and any harmful debris from the surface of your cornea.
- Blurred or Decreased Vision
After a minor corneal abrasion, blurred vision can occur as a result of excess tearing or rubbing your eyes. But, blurred or decreased vision can also be a sign of a more serious injury to the cornea, especially if it continues or gets worse.
Decreased vision might indicate that the inner layers of the cornea, such as the Bowman’s layer or even the endothelium, have been penetrated by the injury. And, as injuries to these inner layers can cause vision loss through scarring or cell damage, it is crucial to seek medical treatment.
- Eye Twitching
Your eye may also twitch or be difficult to keep open as a result of injury to the cornea. This can be in reaction to the pain, which can sometimes be alleviated to some extent by closing your eye. And, sometimes the eye may resort to twitching or excess blinking in an attempt to flush out foreign bodies from the eye.
- Sensitivity to Light
Since the cornea plays a key role in vision through the way it refracts light, damage to the cornea can make it difficult for your eye to take in the light around you, especially if it is very bright.
A scratch on the eye’s surface may also cause this light to refract into the eye in a distorted way, leading to light sensitivity.
And, sometimes, very bright light can be the cause of damage to the cornea, which is why it is important to protect your eyes when you’re outdoors.
- Headache and Fatigue
Exposing your eyes to bright lights or too much screen time can cause headaches and fatigue. And, signs of injury to the cornea such as dry eyes and sensitivity to light can cause these symptoms too.
Causes of Injury to the Cornea
A scratched eye is one of the most common types of eye injuries. But, no matter how big or small, anything which makes contact with your cornea can cause injury.
Everyday things such as workplace debris, sports equipment, makeup tools or a pet can all pose a danger to the sensitive surface of your eye.
Injuries to the cornea may be due to:
- Foreign Bodies: Exposure to something in the eye, such as dust or sand
- Abrasions: Scratches on the surface of the eye
- Chemical Injuries: Caused by fluid entering the eye
- Contact Len Issues: Can be a result of overuse, poor contact lens care, and hygiene, ill-fitting lenses or sensitivity to contact lens solutions
- Ultraviolet Light Injuries: Caused by sunlight, sunlamps or the reflection of light on snow or water
Following any of these forms of injury to the cornea, it’s important to proceed with caution and seek treatment if necessary.
Injury to the Cornea: What to Do
If you scratch your eye or get something in it, if possible, rinse your eye with a sterile saline eyewash or a multipurpose contact lens solution.
You should not rub your eye as this can cause further injury. And, you should not use tap water or even bottled water to flush out your eye. Water can contain microorganisms such as Acanthamoeba. Introducing these pathogens to a scratched eye could result in a serious and even vision-threatening infection.
Do not put a patch over your eye either. Dark, warm places can speed up bacterial growth and increase the chance of infection.
After flushing your eye if pain, redness or the sensation of a foreign body continues, seek immediate attention. Corneal abrasions can cause serious harm in as little as 24 hours so it’s important to act fast.
Treatments for a Scratched Cornea
Treatment for a scratched cornea depends on the cause and severity of the damage. For minor abrasions, non-preserved lubricating drops will be sufficient to keep your eye comfortable and moist while your eye heals itself. Sometimes, your doctor may prescribe antibiotic eye drops to prevent infection during the healing process.
Deeper or larger corneal abrasions may require several treatments. These include an antibiotic ointment which stays on the eye surface longer, a steroid to minimize inflammation and prevent scarring, and something for pain relief and sensitivity to light.
If you seek immediate treatment, most injuries to the cornea result in full recovery with no permanent vision loss. Although, deeper abrasions, especially those in front of the pupil, can leave a scar and decrease visual acuity.
But, if left untreated, some corneal abrasions can lead to a corneal ulcer, which can result in severe vision loss.
Your Guide to Corneal Abrasions and Injuries
As the outer protective layer of your eye’s structure, the cornea is crucial to the proper functioning of the eye, as well as to your vision. Which is why you should seek to offer your corneas this same efficient level of protection and care.
Corneal injuries such as a scratched eye can be minor, but they can also be very serious, especially if left untreated. And, thanks to this guide, you now know the common signs of an injury to the cornea.
If you experience any of these signs of cornea injury, act quickly and cautiously. It could mean the difference between making a full recovery or suffering from permanent vision loss.
For more information, feel free to contact us today with any questions you might have.