The Effect of the AC/A Ratio on the Difference Between Distance and Near Measurements of Deviation

Chris Rubie, Assoc.Dip.O. (Cumb), DOBA

This influence of the AC/A ratio on the difference between the distance and near deviation is investigated in 248 cases. It is found that the AC/A ratio provides a moderately accurate predictor of the near deviation

(± 10Δ) in cases who are orthophoric at 6m. For all other cases it is of no value. The near deviation in most cases was more convergent than that predicted by the AC/A ratio.