Relevant factors of successful surgery in the basic type of intermittent exotropia

Objective To explore the relevant factors of functionally healing the basic type of intermittent exotropia. Methods A prospective observation study was designed.One hundred and thirty-two cases with basic type of intermittent exotropia in Tianjin Eye Hospital from August 2015 to March 2016.Pre- and post-operation examinations to each patient, including the tests of ocular alignment, Worth four-dot test at 2 m and 33 cm, Titmus, functional visual analyzer (FVA), Frisby Davis distance (FD2) were used to explore the influencing factors of postoperative eye position and stereoscopic reconstruction, and to find the cutoff point of surgery.This study followed the Declaration of Helsinki.This study protocol was approved by Ethic Committee of Tianjin Eye Hospital (No.YKLL-2015-8-21). Written informed consent was obtained from each patient or guardian prior to entering study cohort. Results At 6 months postoperatively, there were 84 cases of orthopedic position, 4 cases of overcorrection and 44 cases of undercorrection.The success rate was 63.6%.The deviation at day 1 and peripheral fusion function were statistically significant to postoperative eye position (b=-0.093, P=0.037; b=0.725, P=0.017). The area under the receiver operating characteristic (ROC) curve was 0.645, which showed that the result of Worth four-dot test at 33 cm had lower diagnostic value.Seventy-two cases with eye position between 0 and + 10 PD at 1 day postoperatively were all successful in eye position at 6 months postoperatively.The postoperative eye position was the influencing factor for postoperative distance stereo with FVA (χ2=4.036, P=0.045). The age of onset and the preoperative distance stereoacuity with FD2 were the influencing factors of postoperative distance stereo reconstruction (b=-0.213, P=0.023; b=0.021, P=0.036). The area under the ROC curve of the age of onset and the preoperative distance stereoacuity with FD2 was 0.257 and 0.752, respectively.The former had no diagnostic value, and the latter had a medium diagnostic value.The best cutoff point was 22.5″ with FD2 at 6 m. Conclusions Success rate of postoperative eye position is affected by the postoperative deviation at day 1.The optimal deviation at post-operation day 1 is 0-10 PD.Postoperative distance stereopsis is improved well and the surgery should be done before the distance stereoacuity is decreased to 22.5″ with FD2 at 6 m. Key words: Exotropia/surgery; Oculomotor muscles/surgery; Binocular vision; Stereopsis