Analysis of astigmatism outcomes after horizontal rectus muscle surgery in patients with intermittent exotropia

Abstract

This study examined the factors affecting corneal curvature change after lateral rectus recession and medial rectus resection surgery in patients with intermittent exotropia. This was a retrospective cross-sectional study in intermittent exotropia patients who underwent rectus resection surgery. The study involved 41 male and 42 female patients (mean age: 9.55 ± 5.03 years, range: 3-28 years). Corneal astigmatism analysis was performed using the Galilei G4 Dual Scheimpflug Analyzer. The values of simulated and ray tracing corneal keratometry (K) of astigmatism, including axis changes, were determined preoperatively and at 1 week and 3 months postoperatively. The factors found to affect corneal curvature change were sex, extent of surgery, and axial length. Simulated and ray tracing changes were significant preoperatively and at 1 week and 3 months after rectus resection surgery (p < 0.05); however, there were no differences in astigmatism (D) at any time. The spherical equivalent had a myopic change after rectus resection surgery with cycloplegic refraction, and in ray tracing mode, flat K was decreased at 1 week from baseline and increased 3 months later. Steep, mean K, and axis increased continuously from baseline to 1 week and 3 months. Astigmatism, in contrast, was increased at 1 week, but decreased at 3 months, with no return to baseline. Univariable linear regression analyses showed that the extent of surgery had an effect on flat K change and that sex had an effect on steep K and axis. Additionally, axial length affected steep K and astigmatism, while age had no effect on any variable. Ray tracing values were significantly different from simulated values. In ray tracing mode, rectus resection surgery may result in astigmatism shifted toward with-the-rule, and myopic changes may be caused by differences in thickness and flexibility of the sclera. Notably, age did not affect any variable.

Analysis of the Changes and Possible Reasons in Aberrations before and after Surgery in Patients with Concomitant Exotropia

“…At present, there is no unified conclusion about the change trend, duration, and whether there are different changes in refractive state and corneal curvature caused by strabismus correction. Most of the literature on changes in refraction after strabismus surgery shows that changes in the equivalent spherical lens, drift toward myopia, and an increase in astigmatism can be observed after strabismus surgery [5][6][7][8][9]. Some studies showed that changes in myopia and astigmatism were not statistically significant [19], while others found that changes in myopia drift and astigmatism generally returned to the preoperative level within 3-12 months of follow-up, and some studies described continuous changes [5][6][7][8].…”

“…Although HOAs affect visual imaging quality, previous studies have mainly dealt only with refractive errors after strabismus surgery, not HOAs. ere are reports that surgery can cause transient myopic drift or lead to astigmatism and axial changes in patients, but the effects are transient and reversible [5][6][7][8][9], while others believe that surgery may cause long-term irreversible refractive changes [10]. Some investigators have also not observed differences in equivalent spherical lenses in strabismus surgery [11,12].…”

Refractive changes after strabismus surgery in patients with intermittent exotropia

“…A procedure on the horizontal extraocular muscle can correct exodeviation by altering the action of the extraocular muscle. However, it can also cause changes in the refractive error by reducing the tension of the extraocular muscle transmitted through the sclera to the cornea [ 3 – 6 ].…”

“…Several previous studies have described changes in spherical equivalent after horizontal muscle surgery. Most of them reported a postoperative myopic shift [ 6 – 10 ], although some showed a hyperopic shift or no significant change in spherical equivalent [ 11 , 12 ]. As with the spherical equivalent, an increase in with-the-rule (WTR) astigmatism has been reported in the majority of studies [ 6 – 9 , 13 , 14 ].…”

“…Most of them reported a postoperative myopic shift [ 6 – 10 ], although some showed a hyperopic shift or no significant change in spherical equivalent [ 11 , 12 ]. As with the spherical equivalent, an increase in with-the-rule (WTR) astigmatism has been reported in the majority of studies [ 6 – 9 , 13 , 14 ]. However, previous studies focused on the immediate refractive changes within up to one year after surgery.…”