A Comparison of the Effect of Symmetrical Vs. Asymmetrical Esotropia Surgery on the AC/A Ratio and on the Distance-Near Disparity

A retrospective study of 67 patients undergoing surgery for esotropia (26 bilateral medial rectus recessions, 41 recession/resection) was carried out to evaluate the effect of the surgery on each of two methods of quantifying the relationship between accommodative convergence and accommodation (AC/A): the gradient method and the clinical assessment of the distance-near disparity.Each patient was evaluated by three parameters: the relative effects of both operative procedures on the grade of the distance-near disparity; on the actual numerical reduction of the disparity; and on the gradient AC/A ratio.Neither the ratio by the gradient method nor the distance-near disparity by the clinical assessment method was significantly altered in patients with a normal value by either surgical procedure. In patients with a high AC/A value by the gradient method, there was a tendency towards normalization of the ratio after bilateral medial rectus recession. Only one patient with a high AC/A ratio had a recession/resection procedure.In patients with a high (>9Δ) preoperative distance-near disparity, both the bimedial recession and recession/resection procedures resulted in a signficant prism diopter reduction (P<0.05). While both procedures significantly reduced the postoperative distance-near disparity by grade (P<0.025) as defined by Bateman and Parks, the recession/resection procedure reduced the numerical distance-near disparity by a greater degree than the bimedial recession.