Topical anesthetic induced pain as a diagnostic tool for kerato conjunctivitis sicca (KCS).

Duration and intensity of pain induced by instillation of an acid local anesthetic eyedrop were compared in 321 normals and 77 KCS-patients. The medium duration of pain was increased in KCS-patients (16.23 s) compared to normals (7.64 s). Also the main intensity of pain was increased (KCS: 1.34, normals 0.63). Both differences were highly significant (< 0.001). The sensitivity of duration (limit 12 s) was 64% and the specificity 69%. Except BUT this very simple test is the only one that uses a well defined stress to the tear film to test its capacity for adaptation. Furthermore it is the first KCS-test, that includes the individual sensitivity, which is an important parameter for assessment of KCS-patients.