To observe the outcomes after minimally invasive unilateral recession-resection (R&R) surgery for intermittent exotropia.

The data of 113 patients (113 eyes) who underwent minimally invasive R&R surgery in the Department of Ophthalmology in Peking University People′s Hospital from March 2018 to August 2020 was retrospectively analyzed. Among of them, there were 48 males (48 eyes), and 65 females (65 eyes), with an average age (8.1±3.1) years-old (ranged from 3 to 18 years-old). Before the operation, all patients underwent optometry under ciliary muscle paralysis, and were prescribed glasses according to their age and refractive status, distant and near strabismus were examined under refractive correction. Patients with basic and fusional convergence insufficient intermittent exotropia were selected based on the relationship between near and distant strabismus angle. The core procedure of the minimally invasive operation was to separate and completely resect the check ligaments to reduce adhesions, and the follow-up for more than 6 months. Before and after surgery, patients′ near stereoacuity was measured by a near-stereoscopic sharpness chart, and divergence fusion function, convergence fusion function, fusional range, and distant stereoscopic vision was measured by a synoptophore. The age, disease duration, fusion range, convergent fusion, and divergent fusion were tested for normality, and continuous variables conforming to a normal distribution were described by ±s, and paired t tests were used for pre- and postoperative comparisons. The measurement data such as gender, near stereopsis function, and distant stereopsis function were described by number of cases and percentage. The presence or absence of stereopsis function before and after surgery was tested by Chi-square test.

The average follow-up time for 113 patients was 0.749 years (ranged from 6 months to 3.5 years). After the last follow-up, there were 97 patients (+ 4 PD to -8 PD) with satisfactory outcome, 3 patients with postoperative overcorrection (+ 6 PD to + 8 PD), and 13 patients with undercorrection (- 10 PD to -20 PD). The surgical success, overcorrection and undercorrection rates were 85.8%, 2.7%and 11.5%, respectively. There was a significant improvement in the fusional range from (14.61±8.43) ° preoperatively to (22.70±5.72) ° postoperatively (t=-9.726, P<0.05). 77(68.1%) patients had a near stereoacuity value of 40″ in the last follow-up. 10 (8.8%) patients who had no near stereoacuity before surgery obtained the function after surgery, and the near stereoacuity values can be maintained in the range of 40″ to 200″. At the last observation, 68 (60.18%) patients had improved near stereopsis compared to before, in the range of 200″ to 800″ before surgery and 60″ to 400″ after surgery. For distance stereoacuity, 85(76.6%) patients showed recovery, in the range of 40″ to 800″ before surgery and 40″ to 400″ after surgery. 47(42.3%) patients who had no distance stereoacuity before surgery developed this function postoperatively, ranges from 60″to 800″. There was not a significant difference regarding the presence or absence of stereoacuity using Chi-square test (χ²=1.826, P>0.05).

Minimally invasive unilateral R&R surgery is effective for treating basic and convergence insufficient intermittent exotropia, which has a high postoperative success rate and good binocular functional recovery.