Comparison of surgically induced astigmatism in patients with horizontal rectus muscle recession

Corneal tomography changes following major (6 mm) medial rectus muscle recession: a prospective cohort study using Pentacam®

INTRODUCTION

The aim of this study is to evaluate changes in corneal astigmatism, axial anterior corneal curvature, as well as changes in the anterior chamber depth and central corneal thickness, 2 months following the unilateral recession of medial rectus muscle in children.

METHODS

Thirty-three children with esotropia were prospectively evaluated following unilateral medial rectus muscle recession, using Pentacam®. Comparisons were made between the operated and fellow unoperated eyes, pre, and postoperatively. The assessment was made for changes in the radius of axial curvature on major meridians at 3 and 3.5 mm from the optical corneal center in the mid-peripheral zone. Astigmatism changes of the anterior and posterior corneal surface were calculated using vector analysis software (astigMATIC®). ANOVA model was used to examine the interaction between age or central corneal thickness and postoperative changes in anterior and posterior surface corneal astigmatism.

RESULTS

In the intervention group, changes in anterior and posterior corneal surface astigmatism were statistically significant, with a mean increase of 0.59Dx92 and 0.08Dx91, respectively. In the mid-peripheral corneal zone, there is an increase in the radius of anterior corneal axial curvature more evident nasally 3.5 mm from the corneal center on the horizontal meridian, with corresponding decrease superiorly and inferiorly at 3 and 3.5 mm from the corneal center on the vertical meridian.

DISCUSSION

The changes in total astigmatism of the operated eyes are mainly attributed to the anterior corneal surface. These changes are associated with flattening in the 180 meridian of the cornea, leading to a shift to "with-the-rule" astigmatism.

Changes in astigmatism after horizontal muscle recession strabismus surgery: A retrospective cohort study

Purpose:

The aim of this study was to evaluate the changes in astigmatism after unilateral recession of horizontal rectus muscles in pediatric patients.

Methods:

The authors retrospectively evaluated the medical history of 52 children with esotropia or exotropia, that underwent a unilateral recession strabismus surgery. The intervention group consisted of the 52 eyes that underwent strabismus surgery, and the control group consisted of the other 52 fellow unoperated eyes of the same participants. The intervention group was divided into medial and lateral rectus muscle subgroups, and four subgroups based on the astigmatism axis preoperatively (A: with-the-rule astigmatism, B: no astigmatism, C: intermediate meridians, D: against-the-rule astigmatism). All patients were examined one day preoperatively, and then, six weeks postoperatively. Paired tests were conducted, and the significant level was set to 0.05 or was adjusted for subgroups.

Results:

A mean difference 0.43 D of astigmatism (95% CI: 0.27, 0.59) was observed after the surgery between intervention and control group (P < 0.001). Astigmatism change (postoperative - preoperative) in subgroup A was 0.50 D (P < 0.001) and in subgroup B was 0.75 D (P < 0.001). Moreover, astigmatism changes of 0.50 D were found in both lateral (P < 0.001) and medial rectus muscle group (P = 0.002).

Conclusion:

Strabismus surgery appears to be associated with alterations in astigmatism, and in particular increase in cylindrical power in the eyes that had with-the-rule astigmatism or no astigmatism preoperatively. Those changes should be considered when planning the operation, to avoid transforming clinically non-significant astigmatism into clinically significant.

Transient Increase of Wavefront Aberrations after Horizontal Rectus Muscle Surgery in Exotropia

Aims: Wavefront aberration (WA) has become one of the important indicators for measuring the visual quality. Whether strabismus surgery affects the WA remain controversial. This study aims to investigate the postoperative alterations of WA in patients who underwent horizontal rectus muscle surgery.Methods: A total of 34 patients were enrolled and divided into two groups: bilateral lateral rectus recession (BLR) group and unilateral lateral rectus recession and medial rectus resection (R&R) group. The WA was examined 1 day before surgery, 3 days, and 6 weeks after surgery using the iTrace Visual Function Analyzer (Tracey Technologies).Results: Significant increases in total WA, lower-order aberration (LOA) and higher-order aberration (HOA) of both groups were detected in 3 days after surgery (P < 0.05), while no significant differences in 6 weeks after surgery. Significant increases in astigmatism, secondary astigmatism, and trefoil of both groups were detected in 3 days after surgery (P < 0.05), while no significant differences in individual order of LOA and HOA in 6 weeks postoperatively. Z₂², Z₃³, and Z₄² of both groups increased significantly 3 days after surgery (P < 0.05) and returned to baseline level 6 weeks after surgery, while the rest Zernike coefficients remained the same postoperatively. When comparing the differences between the two groups, there were no statistically significant differences in these parameters between baseline and each follow-up visit postoperatively.Conclusions: The increase of WA restored to pre-operative level in 6 weeks after surgery, indicating the influences of horizontal rectus muscle surgery to WA were transient and reversible.