Cyclopentolate in treatment of sarin miosis.

1. Six young male volunteers were exposed to sarin vapour (isopropyl methyl phosphonofluoridate) at a concentration of 0.5 mg/m(3) for 30 min (concentration time (Ct) 15 (mg min)/m(3)).2. The resulting clinical syndrome was treated by instilling 0.06 ml of a 1% solution of cyclopentolate into the conjunctival sac.3. Visual acuity, retinoscopy, objective and subjective refraction and pupil sizes were noted before the trial, after exposure to sarin and after treatment with cyclopentolate.4. No appreciable difference was demonstrated between the control objective retinoscopy values and those obtained after cyclopentolate treatment of the clinical syndrome induced by sarin. Reduced near visual acuity was observed in some subjects treated with cyclopentolate as compared with acuity after exposure to sarin alone, considered to be due to the partial cycloplegia produced by treatment. Visual acuity after exposure to sarin alone was improved in some instances by the miosis produced.5. It is suggested that unless full dark adaptation is a consideration, treatment of the ophthalmic condition resulting from exposure to this dosage of sarin should be reserved for those experiencing distressing ocular symptoms.