The aim of this study was to investigate the surgical outcomes of the minimally invasive small incision unilateral recession-resection (R&R) for basic-type intermittent exotropia (IXT).

52 patients (52 eyes) with basic-type IXT (-20 PD~-85 PD) who underwent the minimally invasive small incision R&R from March 2018 to April 2019 in Center of Optometry, Peking University People′s Hospital were analyzed retrospectively. Among of them, there were 24 male patients (24 eyes) and 28 female patients (28 eyes), aged 3 to 16 years-old with the average age of (7.3±3.1) years-old. According to the severity of exotropia, patients were divided into small angle group ( A group) and large angle group ( B group). Ophthalmologic and orthoptic examination were carried out, including visual acuity, cycloplegic refraction, motility evaluation, near stereoacuity and fusion function, anterior segment and fundus examination before and after operation for 1 week, 1 month, 3 months and 6 months. The age of onset, course of disease, operation age, diopter and strabismus angle were represent by means±standard deviation and t-test was used to compare; the orthotopic rate and increased rate of near stereoacuity were represented by percentage and chi-square test was used for comparison. The preoperative and postoperative fusion range was used to compare by t-test.

Among of 52 cases (52 eyes) with basic-type IXT, the mean age of patients was (4.7±3.2) years-old, and preoperative exotropia angle was (-38.56±14.96) prism diopter (PD). There was no significant difference in sex ratio(χ²=1.15, P>0.05) and the mean age of patients, course of disease, the average age and cycloplegic refraction between them (t=0.07, 0.02, 0.08, 0.27, 0.28; P>0.05). The preoperative average strabismus of 2 groups were significant difference (t=6.49, P<0.05). Among of patients with R&R, there were 24 cases (24 eyes), 8 cases (8 eyes), 8 cases (8 eyes), 12 cases (12 eyes), 2 cases (2 eyes), and 6 cases (6 eyes) by the lateral rectus 5 mm-medial rectus 4 mm (LR5-MR4), LR6-MR3, LR6-MR4, LR7-MR4 and LR7-MR5, respectively. After opeartion for 6 months, the successful rate of postoperative ocular alignment in A and B group was respectively 82.1% and 79.2% with non-significant difference between them (χ²=0.07, P>0.05). Patients gradually developed exotropia drift from the first week after operation. And the speed of exotropia drift was faster before postoperative 1 month, and then slow down. The preoperative and postoperative fusion range was respectively (14.56±9.53)°and (21.79±6.93)° with significant difference between them (t=4.02, P<0.05). The increased rate of near stereoacuity in A and B group was respectively 53.6% and 75.0% with non-significant difference between them (χ²=2.56, P>0.05).

For basic-type IXT patients with exotropia angle from -20 PD to -85 PD, application of the minimally invasive small incision R&R could achieve a high orthotopic rate, and the fusion function and near stereoacuity were significantly improved after operation. Thus, this surgery could be used as a new choice for basic-type IXT patients.