Forced vergence fixation disparity curves in presbyopia.

Forced vergence fixation disparity curves were measured at distance and near on an asymptomatic presbyopic adult population (average age 62.7 +/- 7.0 years, range 51 to 79). Approximately 42% of the 62-subject sample had the same curve types at distance and near (type I-38.4%; type II-3.5%). Different curve types were found in 58.1% of the sample. Detailed breakdown of the curve types is provided. The results are compared with findings published previously on an asymptomatic prepresbyopic sample of the same size. The necessity to establish normative data for fixation disparity curves at distance and near for different vergence states, age groups, and symptomatic subjects is stressed.