Topical anesthesia of the eye as a diagnostic test

We investigated whether ocular response to topical anesthetic could assist the physician in distinguishing between patients with simple corneal injury and those with iritis, conjunctivitis, or other causes of acute eye pain. Seventy-one patients who presented to the emergency department filled out visual analog pain scores (range, 0 to 10) before and after use of topical anesthetic (proparacaine 0.5%). Mean initial pain scores were higher (6.3 ± 3.0 vs 4.8 ± 2.8, P < .05), final pain scores were lower (1.1 ± 1.7 vs 3.5 ± 2.5, P < .001), and changes in scores were greater (5.2 ± 3.0 vs 1.3 ± 1.3, P < .001) in patients who had simple corneal injury compared with those who had other causes of acute eye pain. By defining response to topical anesthetic as a reduction in pain score by more than 5 (on a scale of 1 to 10) or as a final pain score of less than 1, we found the sensitivity of this test for simple corneal injury to be 80% and the specificity to be 86%. This information is useful to physicians, either with or without a slit-lamp, attempting to diagnose the cause of acute eye pain.