The amount of deviation observed in infantile esotropia is more than 30PD, as shown in many series. In our study, the amount of deviation, on average 45 PD, is compatible with the literature.
Vertical deviations often accompany infantile esotropia. In particular, primary inferior oblique muscle hyperfunction has been reported between 36–78% .6 In our study, the coexistence of 33% inferior oblique hyperfunction was found.
Surgical techniques performed in the treatment of infantile esotropia were bimedial recession and recession and resection procedures in the same eye. Bimedial recession surgery is recommended for these patients in the development age.7,8
Recession is performed by the fixed suture or Hang-Back recession technique with or without adjustable suture. The disadvantages of the hang-back recession are overcorrection of the deviation that occurs especially after the collapse of the center of the muscle. The alphabetic pattern deviation by the upward and downward displacement of the muscle, and the stretched scar formation that occurs in the late period. 9,10,11
Capo et al. published more overcorrection in the Hang-Back recession group in the results they obtained a year after the surgery. They also reported that the overcorrection was caused by the gap formed in the middle of the muscle after recession. 12
In animal experiments with Hang-Back recession surgery, it was observed that the muscle was displaced in the horizontal and vertical axis before adhering to the surgical field. On the other hand, Lee et al. observed no change in four of the ten muscles in their animal experiments, while displacement was observed in four muscles upwards and two muscles downwards. Many explanations have been made to support these results. These are bleeding during surgery and the growth of muscle fibers forward.
Ohtsuki et al. reported that in the Hang-Back recession process, there was more fibrous tissue production around the new adhesion site, which helped the muscle advance forward. 13,14,15 For this reason, a special effort was made to control bleeding in the cases where we performed surgery, and the surgical field was kept clean.
In their animal experiments, Park et al. used fibrin glue as an adjuvant to prevent the horizontal and vertical displacement of the muscle seen in the classical Hang-Back technique. As a result, in the group where fibrin glue was applied, the muscle was more stable in the new insertion site, and less displacement was observed. On the other hand, Chung et al. tried to prevent the movement of the muscle by placing the sutures parallel to the muscle in the modified Hang-Back technique. Their success was 67.4%, and similar to the results of the cases, they performed Hang-Back. 16,17
Ameri et al. reported that they did not see a statistically significant difference in their one-year surgical results in cases where they applied modified and classical Hang-Back recession surgery.18 Unlike the technique of Ameri et al., the sutures we put on the sclera in the new insertion localization are perpendicular, not parallel to the axis of the muscle. In addition, the sutures were placed on the front surface of the muscle, knotted and hung on the original insertion.
Agrawal et al. compared the surgeries performed with the modified Hang-Back technique with adjustable suture to those with classical Hang-Back surgery. They reported that as a result, less adjustment is required, and it is effective for a larger angle of deviation. There was less secondary surgery required during the follow-up and no complications other than the complications seen with the classical Hang-Back technique. 19
In our study, more than 10PD esotropia was observed in nine cases (0.75%) at the end of the first year. Their mean values were 21 (16–35) PD. Small-angle (10PD and below) esotropia was found in 24 cases (20%). Only one case (0.83%) had increased efficacy. According to these results, our success rate is 91.6%, and it is higher than similar study rates in the literature.
It was reported that more stable results were obtained in patients who were operated late period of the life due to the slowing of the growth in the globe.20 In our study, when the preoperative and postoperative deviation degrees of the cases which were operated early and late period of the life were compared. The difference was found to be statistically significant. This result suggests that our technique can be performed safely in cases in both groups. In addition, in our study, the age of surgery was statistically effective on the degree of final deviation (p: 0.037).
According to Kushner et al., there are reverse interactions between axial length and surgical outcome. Surgical doses created by taking into account the axial length may cause different results. In such cases, an increased amount of surgery is recommended. 21 In our study, when the preoperative and postoperative deviation degrees were compared in normal and high hyperopia cases, the difference was statistically significant (p < 0.001). This result shows that the surgical technique we performed is effective independently of the short axial length. The reason for this success is to maintain the contact between the globe and the muscle and to comply with the anatomy. Thus, the effectiveness of the changes in the axial length has been reduced. Also, the effect of refractive error on the final deviation degree was statistically significant (p: 0.039).
Nabie et al. modified the hang-back technique by placing additional scleral sutures parallel to the muscle and compared the results with the classical Hang-Back technique. They did not observe any significant difference between the two techniques in terms of muscle shift, backward movement, pseudotendon formation, and scleral perforation. 22 Similar results were obtained in our study.
The development of exotropia after esotropia surgery is a very common complication. 23–27 In our study, only one patient (0.83%) had orthotropia in the first and sixth months, while 30PD exotropia developed in the first-year follow-up. In the secondary surgery, it was observed that there was a stretched scar syndrome, and orthotropia was achieved due to the advancement of the muscle with scar resection.
Chung et al. compared the classical hang-back technique and the modified techniques in their recession surgery to the medial rectus. In this study, overcorrection was observed significantly in the group applied in the Hang-Back technique. As a result, they showed the continuous friction and movement of the muscle to the sclera. Also, the hematoma developing on the lower surface of the muscle affects the healing process and causes the development of a slipped muscle or pseudotendon. In our modified technique, the intermuscular and check ligaments and the tenon and muscle sheath on the back of the muscle were not touched. According to Repka and Guyton, the backward bending of the middle part of the muscle causes increased effectiveness in the Hang-Back regression technique. In modified techniques, the development of the central cavity and pseudotendon is less frequent. These authors suggested adding 0.5 mm to the standard dose table for recession surgery performed with the Hang-Back technique. 28,29
In our study, only one case (0.83%) had overcorrection. The reason for this low rate is that after placing the vertical suture on the sclera at both ends of the muscle, the same sutures are passed under the muscle again, knotted on the upper surface and suspended in the form of a hammock to the original insertion, thus preventing the muscle from sliding backward. Also, the 0.5 mm overdose recommendation stated in the literature was not followed in these cases.In the traditionally Hang-Back recession surgeries, slipped muscle is seen more frequently due to improper muscle fixing suturation, delayed healing of the muscle, slipping over the globe. This pathology usually occurs in the first few weeks after surgery. One of the aims of our study is to avoid this complication. For this reason, the slipped muscle was not encountered due to the suture we put on the front side of the muscle and hanging from the center of the muscle to the original insertion site.
Studies conducted in the past report that only surgeries applied to oblique muscles cause an insignificant horizontal shift. 30 In our study, it was determined that the surgery applied to the inferior oblique muscle did not have a statistically significant effect on the degree of final deviation (p: 0.566). However, when the patients were examined in the subgroup as those with and without inferior oblique muscle surgery, a statistically significant result was obtained between the preoperative and postoperative deviation degrees in both groups (p < 0.001).