Astigmatic Changes after Horizontal Rectus Muscle Surgery in Intermittent Exotropia

Abstract

PurposeTo evaluate the changes of refractive astigmatism after horizontal rectus muscle surgery in intermittent exotropic children.MethodsSixty-nine exotropic patients were retrospectively reviewed. Of those, 35 patients received unilateral lateral rectus recession (BLR group, 35 eyes) and 34 patients received unilateral lateral rectus recession and medial rectus resection (R&R group, 34 eyes). Non-cycloplegic refractions were measured until 6 months postoperatively. Spherical equivalent (SE), J0 and J45 using power vectors were calculated to determine and compare the changes of refractive astigmatism and axis in both groups.ResultsSE significantly decreased after surgery for the first week and did not changed thereafter in both groups (p = 0.000 and p = 0.018, respectively). In BLR group, J0 showed significant changes at the first week and 1 month after surgery (p = 0.005 and p = 0.016, respectively), but in R&R group, J0 changed significantly between 1 week and 3 months postoperatively (p = 0.023 and p = 0.016, respectively). J45 did not change significantly as time passed in both groups (all p > 0.05). There was no statistically significant difference in the magnitude of changes in SE, J0 and J45 between the two groups after the 6-month follow-up (p = 0.500, p = 0.244 and p = 0.202, respectively).ConclusionsHorizontal rectus muscle surgery in intermittent exotropic children tends to induce a statistically significant change in astigmatism in the with-the-rule direction and myopic shift in SE. This astigmatism change seems to occur within the first 3 months after surgery. Thus, astigmatism induced by surgery should be checked and corrected at least 3 months after horizontal strabismus surgery.

Refractive changes after strabismus surgery

“…described by Hong and Kang [13] increased through the first 3 months of follow-up, and remained stable through postoperative month 6. Preslan et al [4] found that there was still a significant change in WTR astigmatism when patients were re-evaluated 4 months postoperatively, with 11% maintaining at least 1.0 D of astigmatic change and 38% maintaining at least 0.5 D of astigmatic change.…”

“…Studies by both Kwitko et al [6] and Bagheri et al [10] showed a myopic shift that was not statistically significant, whereas others found an initial trend toward myopia that was not sustained when followed for periods of 3-12 months [11 & ,12]. Some research described sustained myopia; Hong and Kang [13] showed a statistically significant myopic shift 6 months postoperatively, with a mean change in spherical equivalent of À0.66 AE 0.84 D after bilateral lateral rectus (BLR) recession and À0.25 AE 1.02 D after recession-resection. This persistent myopic shift was supported by Al-Tamimi et al [14 & ], who showed a mean change in spherical equivalent of 0.14 AE 0.85 D (P ¼ 0.18) 6 months postoperatively.…”

“…However, there is not necessarily agreement that those changes are statistically significant. The WTR astigmatism increase described by Hong and Kang [13] was significant in both BLR recessions as well as recessionresection procedures for exotropia. Preslan et al [4] showed that there was no significant difference in magnitude of refractive changes regardless of whether patients underwent BMR recession, BLR recession, or recession-resection.…”

“…Several groups also looked at astigmatic change in horizontal recession-resection procedures, with some supporting an increase in WTR astigmatism [3,4]. Hong and Kang [13] showed an increase from preoperative astigmatism of 0.43 AE 0.45 D to 0.65 AE 0.39 D (P ¼ 0.016) 3 months postoperatively. Other reports show a small, but statistically insignificant, change in the amount of astigmatism postoperatively [14 & , 16,19].…”

“…When looking at 4-muscle recession in patients with nystagmus, Bagheri et al [12] found a significant increase in WTR astigmatism (þ0.70 AE 0.80 D, P < 0.0002). Hong and Kang [13] used power vector analysis, a method which accounts for both physical and optical properties affecting refraction, to show that WTR astigmatism increased for 3 months postoperatively and was sustained for 6 months of postoperative follow-up. Other studies using vector analysis showed no significant change in postoperative astigmatism after horizontal recessions [10,14 & ,18].…”