Effect of Tertiary and Quaternary Atropine Salts on Absolute Scotopic Threshold Changes Produced by an Anticholinesterase (Sarin)

¹ From the Psychology Branch, Directorate of Medical Research, Army Chemical Center, Maryland

The Hecht-Shlaer adaptometer was employed in conjunction with an artificial pupil of 2-mm diameter to test the effect of a tertiary and quaternary atropine salt on the absolute visual threshold following exposure to isopropyl methylphosphono-fluoridate, an anticholinesterase, and on controls following white light exposure to 3784 ml intensity for 2 minutes duration in human subjects. It was found that protection of both eyes from contact with an atmosphere containing 2.79 mg/m³ Sarin resulted in a significant elevation of the absolute scotopic threshold following exposure by inhalation to the vapor. An intramuscular injection of 2 mg atropine sulfate significantly reduced the elevated threshold whereas an intramuscular injection of 2 mg atropine methyl nitrate had no significant effect. The discussion relates these findings to the process considered critical for visual intensity discrimination.