Contrast sensitivity after wearing prisms to correct for heterophoria

Contrast sensitivity to sinusoidal gratings was measured at spatial frequencies of 1.5-16 c/deg in 8 subjects before and after wearing prisms (for at least two weeks) to correct heterophoria, prescribed by the full correction method of H.J. Haase (Binocular testing and distance correction with the Berlin Polatest [trans. W. Baldwin]. J. Am. Optom. Assoc. 34, 115-125, 1962). At higher spatial frequencies of 12-16 c/deg, we found an average improvement in contrast sensitivity of 0.15 log unit. This effect is estimated to correspond to an increase in visual acuity of 15%.