The benefit of scratch patch testing to demonstrate ocular contact allergy to brimonidine tartrate

Introduction Ocular allergies to brimonidine are frequent in patients treated for glaucoma. There is variability in reporting due to the lack of diagnostic criteria and the absence of cutaneous testing. Many false-negative patch tests (PT) have been described. Alternative methods, such as strip and scratch PT, have been used without a standardized method. Objectives The primary objective is to identify the best method of cutaneous testing and brimonidine concentration for patch testing. The secondary objective is to identify clinical signs and symptoms suggestive of ocular allergy. Patients and Methods A retrospective review of patient files suspected of brimonidine ocular allergy was performed. Patch testing method, brimonidine concentration and clinical symptoms were reviewed. Results Of the 36 patients identified, half tested positive for brimonidine for at least one of the testing methods. The scratch PT demonstrated 17 positive reactions (94% detection rate). Three patients reacted with strip PT. No positive results were found with standard PT. The 5% brimonidine concentration demonstrated the highest sensitivity. The absence of eyelid pruritus was associated with negative testing. Conclusion In the investigation of ocular allergy to brimonidine, scratch PT proved to be an essential tool. Brimonidine 5% pet. appeared as the most sensitive concentration for scratch PT.