The effect of monovision lenses on the near-point range of single binocular vision.

Monovision (MV) contact lenses are commonly used to provide optical correction for presbyopia. Based on their review of the literature on fusional mechanisms, Erickson and Schor predicted that monocular blur associated with MV should not be sufficient to disrupt binocular fusion. We found that fusional vergence ranges in presbyopes corrected with MV were not substantially different from those measured under full binocular nearpoint correction. There were small but statistically significant tendencies for the phoria and base-in vergences to be less exo under MV conditions. Comparisons of findings between a group of successfully adapted MV patients and a group of patients who were unsuccessful with MV indicated no significant differences, suggesting that there is no adaptation effect for these performance variables and that these tests are not effective predictors of MV success.