To evaluate tear eosinophil cationic protein (ECP) as a severity marker for atopic keratoconjunctivitis (AKC) and seasonal/perennial allergic conjunctivitis (SAC/PAC).

Tear ECP levels were measured by chemiluminescent immunometric assay in 7 eyes of 7 patients with AKC, 13 eyes of 13 patients with SAC/PAC, and 10 eyes of 10 healthy control subjects. All AKC and SAC/PAC patients underwent conjunctival injection and papillary formation grading. Tear ECP levels were investigated with reference to the clinical parameters of allergic conjunctivitis (papillary formation and conjunctival injection scoring).

Tear ECP levels in patients with AKC were significantly higher than those in patients with SAC/PAC and in control subjects ( p = 0.012 and p = 0.003, respectively). The number of patients with papillary formation scores of 2-3 was significantly higher in the AKC group than in the SAC/PAC group ( p = 0.016). The number of patients with conjunctival injection scores of 2-3 did not significantly differ between the AKC and SAC/PAC groups ( p = 0.128). All AKC patients obtained papillary formation scores of 2-3, and tear ECP levels in patients with conjunctival injection scores of 2-3 were significantly higher than in patients with scores of 0-1 in the AKC group ( p < 0.001). In the SAC/PAC group, tear ECP levels in patients with papillary formation scores of 2-3 were significantly higher than in patients with scores of 0-1 ( p = 0.046).

This study suggests that tear ECP was a useful marker to diagnose and assess the severity of disease in patients with AKC as well as SAC/PAC. It would be useful to monitor therapeutic outcome in allergic conjunctivitis.