Pre-seasonal treatment with topical olopatadine suppresses the clinical symptoms of seasonal allergic conjunctivitis.

To evaluate the effectiveness of pre-seasonal treatment with topical olopatadine on the reduction of clinical symptoms of seasonal allergic conjunctivitis (SAC). Prospective interventional case series. Eleven patients with SAC received topical olopatadine in one eye at least two weeks before the onset of allergy symptoms, and the other eye served as the control. After the onset of allergic conjunctivitis, both eyes were treated with topical olopatadine. Visual analogue scale (VAS), which evaluated the subjective symptoms of ocular allergy, and the tear levels of histamine and substance P were measured up to six weeks. At the onset of allergy symptoms, the VAS score in the pretreatment eyes was statistically significantly lower than that in the control eyes. The VAS score in the control eyes decreased with time but did not decrease to the level seen in the pretreatment eyes until four weeks later. The tear level of substance P at the onset of allergy symptoms was significantly suppressed in the pretreatment eyes, while the level of histamine was not suppressed. Alteration of the VAS scores in the pretreatment eyes significantly correlated with the level of substance P, but not of histamine. To suppress clinical symptoms in patients with SAC, pre-seasonal treatment with topical olopatadine is effective. The effectiveness of treatment correlates with the tear level of substance P.