Correlation between Frisby-Davis Distance Stereoacuity Scores and Long-term Surgical Outcomes in Intermittent Exotropia

Abstract

Purpose: We analyzed postoperative Frisby-Davis distance (FD2) stereotest scores and changes in the angle of deviation, and the correlation between postoperative FD2 stereotest scores and long-term surgical outcomes, in patients with intermittent exotropia.Methods: This retrospective study included patients aged less than 12 years with intermittent exotropia who underwent at least 28 months of postoperative follow-up. We analyzed the changes in the postoperative angle of deviation and preoperative and postoperative Titmus and FD2 stereotest scores. Surgical success rates at 28 months postoperatively were compared between the good (FD2 at 10 months postoperatively ≤ 10 arcsec) and bad (FD2 at 10 months postoperatively ≥ 15 arcsec) stereotest groups. Surgical success was defined as a horizontal deviation on distance measurement of 5 prism diopter (PD) esodeviation to 10 PD exodeviation at 1 year postoperatively.Results: This study included 101 patients. No significant difference was identified between preoperative and postoperative Titmus test scores. However, the FD2 stereotest scores were significantly improved at 10 months postoperatively (p = 0.001). A significant, positive correlation was observed between FD2 stereotest scores at 10 months postoperatively and the angles of deviation at distance at 10, 16, 22, and 28 months postoperatively (p ≤ 0.001 for all). The surgical success rates at 28 months postoperatively were 73.1% and 43.5% in the good and bad stereotest groups, respectively (p = 0.008).Conclusions: Distance stereoacuity within 1 year postoperatively correlated with the postoperative angle of deviation at distance. Good distance stereoacuity (i.e., < 10 arcsec) within 1 year postoperatively correlated with a higher surgical success rate compared to bad distance stereoacuity.