Atropine eye drops and ocular allergy - what's the cause?

When ocular allergy occurs with low-dose atropine use, how should it be managed? Curious as to whether other clinicians have experienced a similar case, PC posted a photo of a child with red eyes after 2 weeks use of low-dose atropine on our Facebook discussion group.

The key message here is to check for history of recent health issues or other eyedrops used to rule out other possible causes of the red eyes.

1. Allergic reaction to preservative
   Many suggested the allergic reaction is due to preservative toxicity. The type of preservative and its concentration can affect the extent of allergic reaction. Some suggested to contact the compounding chemist to confirm the concentration of atropine and any preservatives used in the drops that were dispensed to the patient. Benzalkonium chloride (BAK), thimerosal and chlorobutanol are the common preservatives¹ in multidose topical eye drops which can be associated with ocular hypersensitive reaction manifested in the forms of ocular dryness, ocular surface damage, blepharitis and contact dermatitis.² The next logical step is then to ensure that non-preservative atropine is dispensed to the patient.
2. Allergic reaction to atropine
   Whilst uncommon, this is still possible. Kothari et al³ describes the common signs and symptoms of allergy to atropine to be itching, burning, periocular redness and eyelid swelling. However, these reactions were not limited to those on preservative-free formulations. They found that the severity of this response was correlated with concentration of atropine echoing the findings in the ATOM2 study⁴ whereby allergic conjunctivitis and dermatitis was noted in the 0.1% and 0.5% group, and none in the 0.01% group. The LAMP study reported 'occurrence of allergic conjunctivitis being similar among all groups' indicating no difference in rates between the placebo, 0.01%, 0.025% or 0.05% formulations.⁵

Some have suggested calling compounding pharmacies to understand their formulation of these drops. The aqueous base, amount and type of preservatives (if any) may vary between pharmacies, so it is useful to understand which other non-active ingredients are going into the drops that are ultimately dispensed to the patient.

1. Consider other differential diagnoses - in this case viral conjunctivitis or another medication toxicity was suggested.
2. It is more likely for a patient to be allergic to preservatives than atropine. As atropine is prescribed in such low concentrations for myopia control, this makes the case for a reaction to atropine quite unlikely.
3. Ensure that the patient is dispensed a preservative-free formulation to avoid potential long-term effects of preservative toxicity.
4. Get familiar with the ingredients (and any preservatives) used in formulations at your local compounding pharmacies.
5. Communicate the symptoms to watch for with potential allergic reactions to the patient and parents, to avoid any nasty surprises down the road.

When to prescribe Atropine for myopia control
Complex Atropine Cases
Complications in atropine compounding

Systemic Side Effects Of Atropine Eye Drops

The Latest And Greatest Research On Atropine

Which atropine dosage should I prescribe for myopia control?

1. Atropine, engaging with science and responsible practice with Professor Karla Zadnik from Ohio State University, USA. (link)

2. More on atropine 0.01% treatment for myopia management with Professor Mark Bullimore from the University of Houston, Texas USA. (link)

3. Atropine 0.01% for myopia management with Professor James Loughman from Technological University Dublin, and the Centre for Eye Research Ireland. (link)