Differential diagnosis in itchy eyes

The question:

A 13-year-old female attends your practice with her mother and explains that she has had blurred vision and bilateral itchy and watery eyes for the past week. She is in general good health, and is not taking any medication. Her mother is extremely anxious and pressures you for a fast resolution. How would you manage?

OT’s panel says...

Ceri Smith-Jaynes: There are three differential diagnoses on my mind: allergic conjunctivitis, blepharitis (and the consequential dry eyes), and infective conjunctivitis. All of these can present with itch as the primary complaint. However, the blurred vision is troubling. Some additional questions will help:

• Do you have a cold or a runny nose? If yes, it could be viral conjunctivitis or allergy

• Is there yellow gunge coming out of your eyes? If yes, I’ll think bacterial conjunctivitis

• Does anyone else close to you have it too? If yes, it’s more likely to be infection, although it could still be allergy

• Do you have any allergies, such as hayfever, asthma or eczema? If yes, it’s a great clue – but she could still have an infection

• Is the itch mostly around your eyelashes? If yes, I’ll suspect blepharitis

• Did it start in both eyes at exactly the same time? If yes, it’s more likely to be allergy

• Any photophobia? Patients with dangerous photophobia usually have sunglasses on in the waiting area

• Do you wear contact lenses?

First things first: I would check acuity, and I might even have to do a refraction. Is this just blur from mucus, which clears with a good blink, or a 13-year-old becoming myopic? Or are there corneal lesions degrading the image? Adenovirus sometimes causes small white lesions in the cornea.

Then, I would perform a slit lamp exam. Molluscum contagiosum on the lids can cause viral conjunctivitis. Blepharitis should be obvious. Papillae and follicles are harder to differentiate. Tiny petechial haemorrhages on the conjunctiva suggest viral infection. Check the cornea for lesions or oedema and instil fluorescein. Long strings of mucus suggest allergy.

There is a small lateral flow test called AdenoPlus, for detecting Adenoviral antigens in tears, but it’s around £15 per test and the sensitivity is <50%.

This is tricky. Without looking, I just can’t tell. If it’s viral conjunctivitis we can only offer cool compresses and lubricant drops for comfort. It’s June, so seasonal allergic conjunctivitis is common; my usual treatment is olopatadine 0.1% eye drops twice a day. This is a combined mast cell stabiliser and antihistamine and works quicker than the over-the-counter eye drops such as sodium cromoglicate 2%, dosed at four times a day. College Guidance does include topical antihistamines for severe itch in viral conjunctivitis. And on the other hand, cool compresses and lubricant drops will help with allergy symptoms.

Kevin Wallace: As usual, Ceri has given us a very thorough answer. My thoughts are similar – particularly this time of year, I regularly see patients with seasonal allergic conjunctivitis. You would expect that the main symptoms of that would be the itching and watering, not blurred vision, so it is important, as always, to consider other reasons for the blurred vision.

If it doesn’t improve with the other symptoms, I would want to see her again to investigate – particularly if it had been a while since her last examination. I probably wouldn’t refract if there is an obvious conjunctivitis, but a pinhole would be useful to see if the vision improves.

A significant factor in my decision making is the patient’s recent history. If they’ve had an upper respiratory infection, I would suspect a viral cause (usually it would have started in one eye, and as Ceri said you may see signs such as petechial haemorrhages).

Without that, I would lean more towards allergy. If I decide that it is an allergy, I would use olopatadine drops, which are very effective in a short time. The main issue with them is that they can only be used for, at most, four months. Fortunately, most just need a few weeks or a month of treatment.

Ankur Trivedi: There has been a recent upsurge in measles cases in certain hot spots around the country, including in the West Midlands and London, so this is where the questioning around general health is pertinent.

It would be unusual, in my limited knowledge of measles, if the ocular symptoms were the sole manifestation, sign or symptom. It does remind me of some anecdotal cases reported in the early pandemic, of COVID-19 presenting with conjunctivitis. I am not sure this ever made it to one of the primary symptoms of concern, however.

If a viral aetiology is suspected, palpating the preauricular lymph nodes to check for tenderness is useful, but this is not present in all cases of viral conjunctivitis.

In this scenario, it is important not to let the pressure you may feel from an anxious parent or carer sway your management plan. I know this can easily happen, especially when children are involved.

In terms of differentiation between papilae versus follicles, I have always tried to look at the vascular appearance – papillae have a central redness with surrounding pallor, while follicles have central pallor with surrounding redness. I do appreciate, though, that it is never that clear cut outside of a textbook.

If you are unsure about how to manage a scenario in practice, contact the AOP’s regulation team by email.