Common eye infections

Welcome to the Australian Prescriber Podcast. Australian Prescriber, independent peer reviewed and free.

Hello I'm Dr John Dowden, the editor of Australian Prescriber. In this podcast I'll be talking to Professor Stephanie Watson from the Safe Sight Institute in Sydney. Professor Watson and her colleagues have written an article on eye infections for the June 2018 edition of Australian Prescriber. Welcome Professor Watson.

Thank you it's a pleasure.

Your article in Australia Prescriber says that conjunctivitis is one of the most common problems seen in practice. Can we therefore assume that people presenting to their general practitioner or community pharmacy complaining of red eyes probably have conjunctivitis?

Look dry eye is another common cause of red eye and it can affect up to one in five people so not everyone with the red eye actually has conjunctivitis.

What are the common causes of conjunctivitis?

A viral infection is the most common cause of conjunctivitis. You can also get a bacterial infection or allergy but these are less common.

It's quite common in general practice certainly to see children with sticky eyes. Can we assume that this is always bacterial conjunctivitis?

It depends on what the stickiness is like. If it's a very young infant or a neonate you have to be wary of the possibility of gonococcal conjunctivitis but in this case you'd have really hyper purulent discharge. Look if it's unilateral in one eye and sort of mucopurulent it can be bacterial but you can get a serous discharge that is sort of a watery discharge in viral conjunctivitis as well.

I think when GPs or pharmacists see someone with a sticky eye they'll make a diagnosis of bacterial conjunctivitis on the history and initial examination but in your article Professor Watson you recommend examination with fluorescein drops. Why do you advise that?

Well this is so you can tell the difference between a corneal infection and a conjunctivitis. Now if you have a corneal infection and it's untreated the patient can lose sight from permanent scarring and severe infection.

Right. I'm just wondering if that is the approach for adults and would you do things differently in children or do you also recommend using fluorescein in children?

Look conditions such as corneal infection can also occur in children. They can also get herpes simplex keratitis, which is a viral infection of the cornea and so it's important to distinguish these just from conjunctivitis.

So now we've made our diagnosis of bacterial conjunctivitis, we've checked that there's no corneal involvement. Is an antibiotic always needed?

If it's bacterial conjunctivitis yes you will always need an antibiotic and an antibiotic will lead to quick resolution of a bacterial conjunctivitis. But if it's a viral conjunctivitis the antibiotics do not really have a role.

Indeed. In Australia Professor Watson antibiotic eyedrops can now be obtained from pharmacies without a prescription. I believe you have some concerns about that.

We have seen cases of delayed presentation of keratitis and poor outcomes associated with the use of antibiotic eyedrops and so if someone has a corneal infection they actually need to be seen by a specialist so a sample can be taken from the eye. And the sample allows us to tell exactly what the infecting organism is so we can give the right treatment. Now patients with corneal infection may have it due to contact lens wear and in these cases the most common organism is Pseudomonas and this is not covered by chloramphenicol, which is the most common antibiotic that's given out over the counter.

So if you were in some doubt about the diagnosis about whether it was conjunctivitis or an early keratitis, prescribing chloramphenicol wouldn't be the right thing to do?

No no it wouldn't cover possible organisms that are causing a corneal infection and may actually delay the patient from seeking further treatment.

Okay, now we've been talking mainly about bacterial conjunctivitis and in adults as you said the problem is usually viral. Now in your article you said that this is usually a self-limiting condition but when would you consider using an antiviral drug for viral conjunctivitis?

Currently there's no antiviral drugs for the most common type of viral conjunctivitis which is adenovirus but if a patient has a herpes simplex infection or herpes zoster then you could use an antiviral that's specific for the herpes viruses and that's something like aciclovir ointment or possibly ganciclovir gel.

Right and I suppose you’d would be looking for any other signs of herpes infections such as cold sores?

Yes it’s important to take a history of cold sores because they may not have a cold sore at the time but they could have had one recently and to look around the skin because sometimes particularly in children they may have vesicular lesions on the eyelid skin.

Yes well as you know herpes involvement in the eye can be very serious. What are some of the other serious eye infections which may present as a red eye?

One of the most serious eye infections is called endophthalmitis and what this is an infection of all layers of the eye and it's serious because the patients can lose sight. For treatment of endophthalmitis patients need to have a sample taken from inside the eye to grow bacteria and then the antibiotics need to be injected directly into the eye. So it's really important not to confuse the two.

Indeed, perhaps for our listeners you could tell us some of the clinical features which might make you think about endophthalmitis. What are some of the risk factors?

The risk factors for infectious endophthalmitis include recent ocular surgery. Cataract surgery is probably the most common operation that practitioners are likely to see but also now there's treatment for macular degeneration which involves injecting anti-VEGF directly into the vitreous and we’re increasingly seeing patients with infection as a result of this.

Yes and I believe the risk of infection increases as the number of injections increases over time.

Yes that's right the risk is cumulative.

Yeah okay. That's a very serious infection which needs urgent referral. You said a little bit earlier about infectious keratitis and it being related to contact lens wear. What other risk factors are there?

So patients that have had trauma are at increased risk for infection. Patients with a history of herpes simplex or herpes zoster keratitis can also get a secondary bacterial keratitis and patients that have had other diseases affecting the front of the eye and this can be things like severe dry eye.

Is keratitis more likely to be seen in patients with diabetes or immunosuppression?

Yes it's also more common in those groups definitely more common in people with diabetes and this can be accompanied by a reduction in the sensation of the cornea which further complicates recovery and treatment.

So you would have a low index of suspicion if the patient was on a immunosuppressant drug or had a history of diabetes?

Yes definitely and with the immunosuppressant drugs the patients can be at increased risk of a fungal infection and this is particularly devastating type of infectious keratitis.

I think it would be appropriate if we conclude today Professor Watson, by getting some advice from you on some of the symptoms and signs which should prompt urgent referral to an ophthalmologist.

It's important to find out about any history of blurred vision. This can indicate corneal involved or endophthalmitis. Other warning signs include severe pain, light sensitivity, opacity of the cornea or what's known as hypopyon, this is a pus level within the eye.

The article you’ve written contains some photographs of some of some of these conditions so if our listeners would like to learn more they can visit the Australian Prescriber website. So thank you Professor Watson for your time this afternoon. It's been a very informative discussion.

Thank you it's a pleasure.

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So, thank you for listening to this Australian Prescriber podcast with Professor Stephanie Watson and me, Dr John Dowden. The views expressed in this podcast are not necessarily those of the Editorial Executive Committee of Australian Prescriber or NPS MedicineWise.