Soft Contact Lenses: Sink or Barrier to Chemical Warfare Agents?

Contact lens wear by United States military personnel in a chemical warfare environment is a controversial issue. Several studies in industrial settings have suggested that contact lenses may safeguard the cornea from chemical and mechanical trauma. The purpose of this experiment was to see if a soft contact lens would act as a barrier to a chemical agent and protect the cornea, perform as a sink and spread the dosage of the chemical agent out over time, or both. Eight subjects were fitted with soft contact lenses (bufilcon A, 45% water content). Subjects wore the left lens only for the study, while the right eye was used for a control. Both eyes were challenged with small volumes (5, 10, and 20 microliters) of a 0.5% physostigmine aqueous solution which was chosen to simulate the live agent diisopropyl fluorophosphate (DFP). Pupil size was monitored over an 8-h period using a modified photoelectric keratometer. The results indicate that a soft contact lens does act as a barrier to chemical agents for the first hour following exposure, but then acts as a sink, spreading out the dosage over time. Soft contact lens; Cornea; Eserine, Physostigmine; Chemical warfare agents; Chemical defense mask.