Clinical Study Of Post-operative Recovery Of Stereopsis In Patients With Intermittent Exotropia Of Different Refractive States

Objective:To observe the recovery of stereopsis in patients with intermittent exotropia（IXT）of different refractive states before and after surgical correction,and to investigate the factors that influence the rehabilitation of stereopsis.Methods:In this prospective clinical study,eighty-six basic IXT patients undergoing strabismus surgery at the department of ophthalmology,Shengjing Hospital of China Medical University from July 2021 to February 2023 were included.IXT patients ranging from 6 to 12 years old were divided into four groups according to pre-operative refractive states:hyperopia group（n=20）,emmetropia group（n=22）,myopia group（n=24）and anisometropia group（n=20）.All patients were examined for distance stereopsis by the synoptophore and near stereopsis by Randot stereotests.The stereopsis examination was taken before surgery and during the follow-up occurring at 1 month,3 months,and 6months after surgery.The surgical outcomes concerning the recovery of stereopsis were compared among the four groups at different follow-up time points.Results:（1）The positive rate of near stereopsis was better than that of distance stereopsis among the groups before surgery（χ²=43.052,P<0.001）,the positive rate of distance stereopsis among the groups with no statistically significant difference（P=0.985）,the positive rate of near stereopsis among the groups also with no statistically significant difference（χ²=4.859,P=0.182）.（2）There was a statistically significant difference in pre-operative near stereoacuity among four groups（F=3.089,P=0.032）,the anisometropia group was worse than the myopia group（P=0.029）.There was a significant difference in near stereoacuity among four groups at post-operative one month（F=2.771,P=0.047）,the anisometropia group was worse than the myopia group（P=0.037）.There was no significant difference in near stereoacuity among four groups at post-operative three months and six months（F=1.980,P=0.123;F=1.895,P=0.137）.Repeated measures analysis of variance was used to compare the recovery of near stereoacuity among the four groups:The near stereoacuity was improved significantly after surgery(F_time=26.021,P<0.001),but the changing rate was at the same among the groups with no statistically significant difference(F_group*time=1.265,P=0.257).（3）The generalized estimating equation（GEE）model was used to compare the recovery of distance stereopsis among the four groups:The distance stereopsis was improved significantly after surgery and the changing rate was not at the same with statistically significant difference(Waldχ_time²=39.187,P<0.001;Waldχ_group²=5.561,P=0.132;Waldχ_group*time²=22.688,P=0.007).Further analysis of the interaction effect indicated that the myopia group with better recovery than the hyperopia group and the anisometropia group at post-operative three months,which differences were statistically significant（Waldχ²=6.362,P=0.012;Waldχ²=5.448,P=0.020）,the myopia group with better recovery than the anisometropia group at post-operative 6 months,which difference was statistically significant（Waldχ²=3.888,P=0.049）.Conclusion:（1）IXT patients exhibited better preservation of near stereopsis than that of distance stereopsis before surgery,and near stereoacuity was more likely to be damaged in patients with anisometropia.（2）Both distance and near stereopsis were improved in IXT patients after surgery.（3）The recovery of near stereopsis showed no significant difference in IXT patients with different refractive states after surgery.In terms of distance stereopsis,myopia performed as a good prognostic factor.