Johnstone M. Kim, MD, is a board-certified ophthalmologist and a practicing physician at Midwest Retina in Dublin, Ohio.

Your eye is red and watery and your vision is blurred. Something is wrong, but you're not quite sure what. Is this a case of pink eye from an infection, allergy, or chemical exposure? Or, could you have a corneal abrasion (scratched cornea), where the top layer of the cornea , the clear dome of the eye, is scraped?

These symptoms could be a sign of either condition. Other signs and symptoms can help to differentiate the two. For example, a thick eye discharge is a sign that you're dealing with bacterial pink eye and not a corneal abrasion.

This article will explore what's involved with pink eye and a scratched cornea, including symptoms, causes, diagnostic procedures, and treatment. Here's what to keep in mind if you find yourself in this situation.

With your eye red and irritated, it may be hard to determine what condition is present. But a scratched cornea and pink eye are very different despite some similar symptoms.

With a scratched cornea, there's an issue with the top layer of corneal tissue. Some of this layer has been inadvertently removed, exposing the tissue underneath, which it normally protects. This is not unlike if you scrape some of the skin off your knee, which, among other things, can be painful.

Pink eye, also known as conjunctivitis , means your conjunctiva (the clear membrane over the white part of the eye) is either infected or irritated. This is something that can happen in one or both eyes.

Your first clue that something is amiss will be when you see a red, tearing eye in the mirror. Both a corneal abrasion and pink eye can have overlapping symptoms.

If you have a corneal abrasion, the symptoms will be in only one eye. Symptoms you're likely to have include:

In cases of pink eye, the following symptoms may occur in one or both eyes:

One of the things that can distinguish these two conditions can be the cause. If you know that something physical happened to your eye just before the symptoms started, that may mean you're dealing with a corneal abrasion. But if friends and family members also have similar complaints, it's likely pink eye, which can be contagious.

Consider some of the causes of each.

This can occur after something has gone into the eye, such as a tree branch, fingernail, or even some sand or grit. It can also happen from wearing contact lenses. People who rub their eyes or have dry eyes may also be vulnerable to corneal abrasions.

Conjunctivitis can come from several different causes. It can be caused by a virus or bacteria, which can spread easily from person to person. Allergies, such as to pollen, animal dander, or dust mites, may cause it. Chemical irritation, such as chlorine in pools or cigarette smoke, may also be a cause.

Figuring out whether you have a scratched cornea or pink eye will begin with taking a detailed history of how it may have occurred. Then, a healthcare practitioner may perform certain tests. Here's what to expect.

If your eye doctor (ophthalmologist or optometrist) suspects that you have a scratched cornea, they will likely put fluorescein dye on your eye to indicate where the damaged tissue is located. They can see this by shining a special blue light on the area, making any abrasion glow green.

Don't be surprised if they put you in front of what's known as a slit lamp to take a closer look at the eye. This uses a strong light source and a microscope to allow a detailed look at the eye's surface.

A healthcare provider will usually diagnose pink eye based on your history, symptoms, and examining the eye. If the pink eye is not going away on its own, they may culture the eye to determine the cause. This can help guide treatment.

After making the diagnosis, a healthcare provider will tailor treatment to your unique circumstances.

If you have a scratched cornea, potential treatments may include the following:

With pink eye, the treatment approach will vary depending on the type, including:

A scratched cornea and pink eye may look similar when you have a red, teary eye. The conditions have very different causes. A detailed history of what happened before symptoms were noticed may help distinguish between the two.

A scratched cornea is usually preceded by some kind of poke in the eye that temporarily removes the top corneal layer. Pink eye may be caused by bacteria, viruses, allergies, or chemical irritants. Each condition needs to be properly diagnosed, and treatment should be tailored to your unique situation.

Realizing that your eye is red and teary and that you may have either a scratched cornea or pink eye may concern you. The good news is that in most cases, once either is properly diagnosed, it can be effectively treated. Your eye problem should soon clear up and return to normal.

Yes. Some of the symptoms, such as having a red, teary eye, are similar. But the causes are very different.

Either bacterial or viral pink eye can be contagious. Bacterial pink eye is contagious from when symptoms first appear and for as long as you have discharge. If you take antibiotics, you will be contagious for up to 24 hours after you begin the treatment.

Viral pink eye can be contagious for the entire time you have symptoms until this eventually clears up, which may take from several days to a couple of weeks. Other forms of pink eye are not contagious. The virus can also stay on surfaces for up to two weeks.

If you have pink eye, you generally have red, teary eyes with slight swelling and discharge. In some cases, your lids may also be puffy with some crusting near the lashes.

Usually, there are no long-term complications with pink eye. But if it becomes a chronic condition, with lingering inflammation, it could cause permanent vision issues.

Corneal abrasions usually do not cause any permanent damage. However, a deep scratch may cause corneal scarring, which can result in permanently hazy vision.

In many cases, if the scratch is minor, it can heal by itself. But it's still important to have an eye doctor check this out. They can prescribe antibiotic drops to make sure you don't also develop an infection and may also offer pain relievers.

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Wills Eye Hospital. Corneal abrasion.

American Academy of Ophthalmology. Conjunctivitis: what is pink eye?

American Academy of Ophthalmology. Corneal abrasion and erosion.

Centers for Disease Control and Prevention. Conjunctivitis (pink eye).

University of Pittsburgh Medical Center. How long is pink eye contagious?

Johns Hopkins Medicine. Pink eye.

Columbia University. Corneal disease, facts about.

American Academy of Ophthalmology. First aid for eye scratches.

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