The effects of a single intramuscular injection of atropine sulphate on visual performance in man

The effects of a single intramuscular injection of 2 mg atropine sulphate on visual function were studied in volunteer subjects. The well-known effects of increased heart rate, dryness of the mouth, increased pupil diameter and reduced accommodative range were confirmed. Visual acuity, stereoacuity, red-green colour balance and reaction time to a visual stimulus were unaffected by atropine, while extraocular muscle balance (horizontal heterophoria and cyclophoria) underwent a transient change. There was no significant change in contrast sensitivity measurements to stationary sinusoidal grating patterns of spatial frequencies 1-30 c/deg; however contrast sensitivity to moving grating patterns of spatial frequencies 1-5 c/deg showed a sustained reduction which was still present at 6 h post-injection. It is concluded that atropine adversely affects movement detection but not stationary visual function.