IN-VITRO ALTERATION OF SCHIRMER TEAR STRIP WETTING BY COMMONLY INSTILLED ANESTHETIC AGENTS

The Schirmer's tear test is often performed with topical anesthesia to reduce reflex tearing. Fluress (Barnes-Hind, Sunnyvale, CA, U.S.A.) a nd Fluoracaine (Akorn, Abita Springs, LA, U.S.A.) are commonly used an esthetic-fluorescein preparations that contain viscous additives. Beca use the rate of Schirmer's strip wetting is dependent on capillary act ion, a property related to solution viscosity and surface tension, spu rious results may be obtained if these agents are used for anesthesia. We report in vitro Schirmer's strip wetting rates for various concent rations of Fluress and Fluoracaine, as well as pure fluorescein soluti on using a tear substitute (Dacriose; IOLAB, Claremont, CA, U.S.A.) as a diluent. Results showed a direct concentration-dependent reduction of Schirmer's strip wetting with time for both Fluress and Fluoracaine dilutions compared with Dacriose alone (p < 0.001) or Dacriose-fluore scein solutions (p < 0.001). In addition, Schirmer's wetting with Dacr iose-fluorescein solutions caused a separation of the Dacriose and flu orescein wetting fronts (p < 0.001) but did not affect the overall Dac riose wetting. These data have clinical implications concerning false- positive results when testing for dry eyes.