The ratio of accommodative convergence to accommodation (AC/A ratio) was tested in five normal subjects and nine patients with intermittent A- or V-patterns to determine whether or not the accommodative convergence relationships varied in different vertical positions of gaze and thus could be considered of etiological significance in this condition. No difference was found between the AC/A ratios in upward and downward gaze in the normal group or in any of the nine patients studied. In those with V-exotropia, the ratios ranged from abnormally high to abnormally low values. The A-exotropes had normal or slightly high values. The one patient with V-esotropia had AC/A ratios within the normal range.
PAYNE JW, von NOORDEN GK. The Ratio of Accommodative Convergence to Accommodation in Strabimus With A- and V-Patterns. Arch Ophthalmol. 1967;77(1):26-28. doi:10.1001/archopht.1967.00980020028007