Changes in lateral ocular movement after two muscle exotropia surgery

Objective

This study was to identify the surgical procedures associated with changes of lateral eye movement to help inform surgical planning for patients with concomitant exotropia.

Methods

The medical records of 87 concomitant exotropia surgical procedures that were performed at Henan Eye Hospital from June 2014 to August 2015 were retrospectively reviewed.The deviation angle was measured by prism and alternate cover test.Photographs and arc campimeter was used to obtain changes of abduction and lateral monocular fixation field respectively.Data were compared preoperatively and postoperatively among five groups based on the surgical procedures.The surgical procedures were 0 mm for control group (61 eyes), 8 mm unilateral rectus recession for lateral rectus recession (LR) group (27 eyes), 5-6 mm recession/4-5 mm resection for small amount recess-resect (R-R) group (24 eyes), 7-8 mm recession/5-6 mm resection for medium amount R-R group (29 eyes) and 8-10 mm recession/7-8 mm resection for large amount R-R group (33 eyes). The minimum follow-up period was 6 months.Informed consent was signed from each patient or the guardian.

Results

The success, overcorrection and undercorrection rate was 81.61%, 5.56% and 12.64%, respectively.Mean preoperative abduction of each group was (11.86±1.11)mm in the control group, (12.04±0.68)mm in the LR group, (11.58±1.06)mm in the small amount R-R group, (11.86±0.93)mm in the medium amount R-R group and (12.22±0.60)mm in the large amount R-R group.The postoperative mean abduction of each group was (11.81±1.03), (11.81±0.70), (10.78±1.05), (10.54±1.07) and (9.90±0.82)mm, respectively.Mean abduction among the five groups was not significantly different preoperatively (F=1.85, P=0.12), while it was significantly different postoperatively (F=28.04, P=0.00). The abduction between control group and small amount R-R group was not significantly different postoperatively (P=0.99), but the abduction of control group was significantly greater than that of all the R-R groups (all at P=0.00). Mean lateral monocular fixation field of each group preoperatively was (50.82±3.30)° in control group, (51.48±2.39)° in LR group, (50.13±3.51)° in small amount R-R group, (51.06±2.90)° in medium amount R-R group and (52.09±2.61)° in large amount R-R group.The postoperative mean lateral monocular fixation field of each group was (50.52±3.51)°, (50.11±2.36)°, (46.38±3.67)°, (44.00±3.00)°, (41.84±2.46)°, respectively.Preoperative lateral monocular fixation field among the five groups was not significantly different (F=1.75, P=0.14), while postoperative difference was significant (F=55.75, P=0.00). Lateral monocular fixation field between control group and LR group was not significantly different postoperatively (P=0.57), but the mean lateral monocular fixation field of control group was significantly greater than that of all the R-R groups (all at P=0.00).

Conclusions

The successful alignment rate of unilateral recess/resect procedure is satisfying, but it can also create abduction deficit especially in large surgical amounts eye.Patients with binocular vision will be sensitive to diplopia in side gaze; in such cases, the consequences of recess/resect procedure should be considered particularly to avoid decrease of the binocular single vision field.