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How to know if you have conjunctivitis

How do I know if my red eye is conjunctivitis?

Many things could cause you to have a red eye, one of which is conjunctivitis.
Here are the four main causes of a red eye where the conjunctiva, which is the covering of the white of the eye, is pink or red:

There is also, of course, the hay fever type red eyes and puffy eyelids.
These eye complaints are all treated differently. A red eye is a very common problem presenting to primary eye care clinics, and fortunately, most cases are not sight-threatening. However, one must be alert to the red-flag signs to recognize when this might be a possibility.

Infective conjunctivitis

The conjunctiva is the thin white mucosal covering of the white of the eye and the inside surfaces of the upper and lower lid. Infective conjunctivitis is common and self-limiting in the majority of cases. Bacterial infections are by far more common in children than viral ones and, in adults, viral conjunctivitis is more common. The symptoms of infective conjunctivitis are the red eye which is usually bilateral together with watering, discharge, and itching or burning. There may also be crusting of the lid margins and associated general flu-like symptoms either at the same time or preceding conjunctivitis.
In general, bacterial conjunctivitis is sticky and viral conjunctivitis is watery.
You will see with infective conjunctivitis as a diffuse redness across the conjunctiva especially in the lower conjunctiva and just inside the lower lid what is called the tarsal conjunctiva.
The tarsal conjunctiva is the posterior surface of the lower lid. If there is bacterial conjunctivitis, the discharge is often mucopurulent. This means it is white, yellow or green and sticky and can stick the eyes together in the morning. If the eye is only watering, then it is very likely to be viral conjunctivitis.
Bacterial conjunctivitis is often self-limiting, but topical lubricant drops and antibiotics will help to soothe and ease the itch, redness, and discharge. It is advisable to restrict the use of topical antibiotics to the more severe cases because of the risk of antibiotic resistance developing.
If it is viral conjunctivitis, then topical lubricants will help to soothe it as antibiotics will not be effective. Just occasionally antibiotics are prescribed, and even a small amount of steroid eye drops for symptomatic relief under the care of the ophthalmologist, when the conjunctivitis is more severe.
Infective conjunctivitis is usually bilateral but can be more severe in one eye than the other, or start in one eye then spread to the other eye.


The second cause of a red eye that is very common is a subconjunctival haemorrhage. You may well think that you have conjunctivitis when you see a localized dense, red haemorrhage on the conjunctiva, but often this is just a painless localized small haemorrhage on the surface of the otherwise completely normal eye. It is quite common and usually occurs with straining or coughing or catching the eye with a finger, and it is self-limiting, resolving in 10 to 14 days.
However, it can be quite alarming because of its sudden onset and often incidental finding. It may well be more common in people that have high blood pressure. If you are worried about your red eye and want to know whether it is a subconjunctival haemorrhage or conjunctivitis you can see your ophthalmologist. Sub-conjunctival haemorrhage is usually unilateral.

Acute anterior uveitis

This complaint is less common than conjunctivitis and has a different pattern of redness where the redness is around the edge of the iris on the white of the eye. This is called circum-ciliary injection in medical terms. There can be associated watering and photophobia, but no sticky discharge.
Acute uveitis requires the input of a general ophthalmologist to start treatment. It will not resolve by itself, and it requires eye drops and possibly investigation if it recurs, and then a more specialist ophthalmological opinion is required.
Photophobia is a predominant symptom in anterior uveitis and if you have that you should seek an ophthalmic opinion to exclude anterior uveitis. Untreated, anterior uveitis can become more severe and even cause damage to the eye, and have secondary effects on the eye with reduced vision. Anterior uveitis is usually unilateral.

Eye drop toxicity

The cause of a red eye and red periocular skin can be an allergic response to eye drops, particularly if the skin around the eyes is red, dry and flaky. It is a contact dermatitis and will respond well to removal of the offending cream or eyedrop, and local treatment with hydrocortisone cream on the eyelid skin. It is usually bilateral.
Hay fever-related allergic conjunctivitis is widespread and affects about 20% of the population. The condition is common in people who are atopic and who may have a tendency to suffer from eczema or asthma. The predominant symptom is itching and watering and the eyes can be quite pink or red. It is usually bilateral. The eyelids are a bit puffy and the conjunctiva can swell up. Allergic conjunctivitis is often seasonal, in which case it is called hay fever, or it can be all the year round when it is called perennial. Allergic conjunctivitis can cause scarring if severe and then requires an ophthalmology assessment.

How to know if you have conjunctivitis?

If your eye, or eyes, are red and sticky or watery and a little itchy then you most likely have infective conjunctivitis, which could be bacterial or viral. To get advice on the management of your conjunctivitis to confirm the diagnosis and exclude other causes of a red eye, such as subconjunctival haemorrhage, acute uveitis, eye drop toxicity and allergic conjunctivitis, you should seek urgent eye care with an ophthalmologist.
The red flags in a patient are photophobia, a painful unilateral red eye with blurred vision or an abnormal pupil shape. If you have any of those features, you should be seen in your local accident and emergency department or urgently by the specialist ophthalmologist.


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