The extent to which compensation for the prismatic effects of spectacle lenses is maintained

Purpose. The ability of subjects to compensate for the visual displacement caused by the prismatic effects of spectacle lenses was studied over 4 days . Methods. Subjects were made myopic using contact lenses and then correcte d with spectacles. Pointing behavior was used to assess directional localiz ation. Compensation for the refractive lenses was induced by showing subjec ts their pointing errors, Results. Compensation was maintained for 4 days i n 3 of 4 subjects despite 24 h of normal viewing between testing sessions. One subject demonstrated a negative directional aftereffect which has not b een previously reported in studies of spectacle lens adaptation, Conclusion s. Compensation for the prismatic effects of spectacle lenses can be mainta ined for several days in some subjects. This compensation may be functional ly useful for some patients who switch between spectacles and contact lense s.