|Year : 2017 | Volume
| Issue : 3 | Page : 100-104
Refractive error changes after bilateral medial rectus muscle recession surgery in congenital esotropia
Walid Mohamed El-Zawahry MD
Department of Ophthalmology, Faculty of Medicine, Ain Shams University, Cairo, Egypt
|Date of Submission||10-Jun-2017|
|Date of Acceptance||21-Jul-2017|
|Date of Web Publication||6-Nov-2017|
Walid Mohamed El-Zawahry
Department of Ophthalmology, Faculty of Medicine, Ain Shams University, Abbassia Square, Cairo, 11371
Source of Support: None, Conflict of Interest: None
The aim of this study was to evaluate the changes in refractive errors after bilateral medial rectus muscle recession surgery in children with congenital esotropia.
Patients and methods
Medical reports of 75 children with congenital esotropia were retrospectively reviewed. All included patients attended the Ain Shams University hospitals for undergoing bilateral medial rectus muscle recession surgery from January 2013 till January 2016. Cycloplegic refraction was done preoperatively and 3 months and 1 year postoperatively. Spherical equivalent (SE) was calculated to determine the amount of change in refractive error especially astigmatism and its axis. Patients were excluded if neurological abnormalities or developmental delays were documented and if structural eye abnormalities were present.
Significant myopic shift and astigmatic change were determined in the SE refraction in the early postoperative period (3 months); however, these changes disappeared in the long term (at the postoperative first year).
Only the early postoperative period showed significant change in the SE value with myopic shift that necessitates early postoperative visual rehabilitation for fear of recurrence of the deviation or development of amblyopia.
Keywords: bilateral medial rectus muscle recession, congenital esotropia, refractive error
|How to cite this article:|
El-Zawahry WM. Refractive error changes after bilateral medial rectus muscle recession surgery in congenital esotropia. J Egypt Ophthalmol Soc 2017;110:100-4
|How to cite this URL:|
El-Zawahry WM. Refractive error changes after bilateral medial rectus muscle recession surgery in congenital esotropia. J Egypt Ophthalmol Soc [serial online] 2017 [cited 2018 Mar 17];110:100-4. Available from: http://www.jeos.eg.net/text.asp?2017/110/3/100/217700
| Introduction|| |
Changes in the refractive and astigmatic status following routine strabismus surgery have been reported and can occur even after successful surgery as demonstrated in different studies ,,,,.
These changes can affect the visual acuity and may lead to serious postoperative complications such as amblyopia, change in the angle of deviation leading to consecutive strabismus, or recurrence of deviation, unless detected and precisely corrected , and as children are the majority of population undergoing this surgical procedure, close monitoring and follow-up postoperatively is considered crucial.
Although the etiology of refractive changes following strabismus muscle surgery is debatable and controversial in the literature, some reports found that the tension applied on the corneal meridian is emphasized as the most important risk factor ,.
Regarding the effect of operating upon the extraocular muscles on refraction, some reports found that spherical equivalent (ES) either did not change ,, changed in a myopic direction  or changed in a hypermetropic direction . Others reported long-term and significant refractive changes ,,,. Part of these discrepancies may be attributed to methodological difficulties in representing refractive power changes.
This study investigated the effect of bilateral medial rectus (BMR) muscle recession surgery on the postoperative refraction at two time points (3 months and 1 year) and explained the detected effect using statistical methods.
| Patients and methods|| |
In this retrospective study, medical records of 75 children with esotropia (ET) attending the Ain Shams University hospitals, who underwent BMR muscle recession surgery from January 2013 to January 2016 were evaluated. Their age ranged from 4 to 6 years (48–72 months).
Exclusion criteria included patients with amblyopia, vertical deviation, organic eye pathology, or neurologic or systemic diseases, and those who did not follow the scheduled visits after surgery.
Preoperatively, all patients received a thorough and comprehensive ophthalmological examination, which included cycloplegic refraction, best-corrected visual acuity, slit lamp, and fundus examination, and alternate prism cover test at distance and near with and without cycloplegic refraction was given for those who needed glasses accordingly for at least 1 month.
Then the patients underwent BMR recession through Swan conjunctival incisions and hang-back scleral fixation technique under general aesthesia.
Patients were then examined 1 week, 1 month, 3 months, and 1 year postoperatively. At each visit, the measurement of angle of deviation was done using alternate prism cover test.
Measurement of refractive errors at each time point was performed through cycloplegic refraction using conventional portable autorefractometer (AR1; Nidek, Gamagori Aichi, Japan). A median value of cylinder and its axis was selected based on the reading for co-operative kids, whereas for uncooperative kids, it was done for them under general anesthesia.
Statistical analysis was performed with SPSS version 13 statistical software for Windows (SPSS Inc., Chicago, Illinois, USA) as follows:
- Qualitative values were described as numbers and percentages.
- Quantitative values were described as means and SD.
- Paired t-test and repeated measures analysis of variance were used to compare changes of variables [sphere (S), cylinder (C), and spherical equivalent (SE)].
- Repeated measures analysis of variance was used to compare the three points of measure (preoperative, 3 months, and 1 year), whereas paired t-test was used to compare between the differences at two points of measure.
The confidence interval was set to 95%, and the margin of error accepted was set to 5%. So, the P value was considered significant as the following:
P more than 0.05 was considered nonsignificant.
P less than 0.05was considered significant.
P less than 0.01was considered highly significant.
| Results|| |
Among the 75 patients included in this study, 44 (59%) were females and 31 (41%) were males as shown in Graph 1, with the mean age of 5 0.4±15.55 months, ranging from 24 to 72 months
Mean age at time of surgery was 19.52±11.26 months, ranging from 48 to 72 months.
Preoperative and postoperative S values showed highly significant change toward the hypermetropic side (P<0.001), whereas the preoperative and postoperative mean cylindrical power of astigmatism (C) preoperatively showed significant change toward the myopic side (P=0.004) ([Table 1]).
|Table 1 Mean values of preoperative and postoperative changes of spherical equivalent and astigmatism power|
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Regarding the mean SE preoperatively, it showed highly significant changes toward the myopic side (P=0.000) ([Table 1]).
Regarding difference between variables at each time point, difference of mean S values between preoperatively and 3 months postoperatively was significant (P= 0.030), difference between preoperative measures and 1 year postoperatively was highly significant (P=0.000),whereas the difference between 3 months and 1 year postoperatively was highly significant (P=0.00) as well.
Significant difference at of C values was found between preoperatively and 3 months postoperatively (with P=0.04,) whereas nonsignificant difference was found between preoperatively and 1 year postoperatively (with P=0.916), and also between 3 months and 1 year postoperatively (with P=0.124).
Concerning the SE values, nonsignificant difference was noted between preoperatively and 3 months and 1 year postoperatively (with P=0.088 and 0.292, respectively); however, a highly significant difference was noted between measures of 3 months and 1 year postoperative time points (with P=0.005).
These were illustrated in [Table 2] and Graphs 2-4
| Discussion|| |
Refractive power changes following strabismus surgery have been reported, but the results were debatable. With-the-rule astigmatism after horizontal rectus muscle surgery was frequently observed, but most of the studies evaluated the mean change of astigmatism through using corneal topography or keratometry for elderly patients. Few authors were interested in evaluating the changes in refraction and astigmatism following (BMR) muscle recession surgery, and studies are very limited particularly in children with congenital ET.
Hong and Kang  reported that astigmatic changes and myopic shift in SE could be observed after horizontal strabismus surgery and that patients should be monitored for refraction at least 3 months after surgery.
Preslan et al.  observed astigmatic shift in patients undergoing strabismus surgery and reported that these changes persisted throughout the 4-month period of their study with small variations.
Rajavi et al.  found significant myopic shifts in SE at 1 month postoperatively and in C at both 1 and 3 months postoperatively in eyes that underwent medial rectus muscle recession.
Nardi et al.  determined that increase in C was higher in patients undergoing medial rectus muscle recession than in patients undergoing lateral rectus muscle recession. They also reported that the C change detected 1 day after surgery decreased over time, and the rate of patients with residual astigmatism of more than 1 D at 30 days after the surgery was 6%.
The number of studies on the long-term monitoring of postoperative visual functions is limited. Fujikado et al.  evaluated refractive error preoperatively and postoperatively in patients undergoing ET surgery and found the rate of anisometropia of 2 D or greater to be 23% in more than 3 years of follow-up.
In this study, compared with the mean SE value in the preoperative period, the measurement of mean SE value at 3 months postoperatively revealed highly significant myopic shift of ∼0.91 D,whereas the measurement at 1 year postoperatively revealed significant myopic shift of ∼0.45 D. Comparison of the results at 3 months and 1 year postoperative time points revealed change of the SE of ∼0.45 D; this means that the change occurred in the early postoperative period and remained constant in the long term with no changes being noticed between the 3-month and 1-year postoperative time points.
This matched well with the study by Isil et al. , in which they reported significant myopic shift, and C change were determined in the SE refraction in the early postoperative period (first month); however, these changes disappeared in the long term (at the postoperative first year). This may be attributed to the decrease in the effect of recessed muscle on the cornea and reversal of this effect at the end of the first year.
In summary, postoperative evaluation of 25 patients who underwent (BMR) muscle recession surgery revealed significant myopic shift and astigmatic change in SE in the early postoperative period (3 months); however, these changes disappeared in the long term. These changes were considered to be associated with alterations in the tension applied by the recessed muscle on the cornea.
| Conclusion|| |
Only the early postoperative period showed significant change in the SE value with myopic shift that necessitates early postoperative visual rehabilitation for the fear of recurrence of the deviation or development of amblyopia.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]