|Year : 2018 | Volume
| Issue : 2 | Page : 49-52
Risk factors for consecutive esotropia
Manal A Kasem
Department of Ophthalmology, Mansoura Ophthalmic Center, Mansoura University, Mansoura, Egypt
|Date of Submission||06-Apr-2018|
|Date of Acceptance||16-May-2018|
|Date of Web Publication||30-Aug-2018|
Manal A Kasem
Dakahlyia, Gomhoria Street, Mansoura City 35511
Source of Support: None, Conflict of Interest: None
Purpose The aim of this retrospective study was to investigate the different factors predisposing to consecutive esotropia (CET) after surgical management of intermittent exotropia (IXT).
Patients and methods This study included the medical records of patients who had surgery for IXT from March 2016 to March 2017. Postoperatively, the patients were divided into two groups: A group who developed CET and another group who became orthotropic within 6 months of follow-up. Possible risk factors for the development of CET were recorded and analyzed.
Results Eighteen patients developed CET, while the orthotropic group consisted of 78 cases. CET occurred in 61% of patients of less than 6 years old. There was no significant correlation between preoperative angle of IXT and development of CET, but there was significant correlation with the angle of initial CET (postoperatively). CET was found in 16.7% of preoperative tenacious proximal convergence exotropia. CET was developed in 66.7% of cases of asymmetrical surgery (recession–resection), and more common with the development of lateral incomitance (27.8%). Amblyopia, suppression, and absence of stereopsis were considered risk factors in 50% of the cases. No correlation between errors of refraction and development of CET.
Conclusion This study concluded that many risk factors may predispose to CET, the more significant factors were the age of the patients (<6 years old), large angle of initial postoperative CET, type of IXT, asymmetric surgery (recession–resection procedure), development of lateral incomitance, and presence of amblyopia or suppression.
Keywords: consecutive, esotropia, risk
|How to cite this article:|
Kasem MA. Risk factors for consecutive esotropia. J Egypt Ophthalmol Soc 2018;111:49-52
| Introduction|| |
Prevalence of consecutive esotropia (CET) ranged from 2% up to 20% due to overcorrection of previously existing exotropia ,. Occurrence of CET represents a cosmetic problem for the patients, and may suffer from diplopia. Also suppression, amblyopia, and deterioration of stereopsis may occur later especially in children . The initial postoperative CET was controversial; some studies found that the management of exotropia with overcorrection within 20 prism diopter (PD) immediately after surgery was preferable for the prevention of recurrence of exotropia ,,. While Raab and Parks  reported that the overcorrection of more than 17 PD will increase the incidence of CET, other reports found that CET may develop in patients with immediate overcorrection or even after long follow-up ,. The aim of this study is to investigate the different factors predisposing to the development of CET after surgical management of intermittent exotropia (IXT).
| Patients and methods|| |
Patients who underwent surgery for IXT by a single surgeon (K.M.) through the period from March 2016 to March 2017 at Mansoura Ophthalmic Center were reviewed retrospectively. The records include: sex, age at the onset of consecutive deviation, uncorrected and best corrected visual acuities, cycloplegic refraction, and prism cover test for the measurement of angle of deviation. Also details of previous surgery for IXT was recorded including the age at the time of surgery, type of surgery (bilateral lateral recession or recession–resection), amount of muscle surgery (amount of recession or resection), associated errors of refraction and amblyopia, state of binocular vision (suppression, fusion, and stereopsis), and the angle of exotropia before surgery. The data were recorded at least after 6 months of follow-up of the surgery for IXT. CET was defined as persistent esotropia of more than 10 PD developed postoperative correction of IXT and recorded within 6 months of follow-up.
Patients of previous multiple surgeries, restrictive strabismus, mental retardation, and cerebral palsy were excluded. Also cases associated with oblique muscle dysfunction or dissociated vertical deviation were excluded.
- Age of the patient was categorized into before 6 years and after 6 years (schooler age).
- Amblyopia which was defined as a difference of best corrected visual acuity between both eyes of two or more lines in Snellen visual acuity charts.
- Lateral incomitance which indicated overcorrection.
- The types of exotropia either the basic type, the convergence insufficiency type, the tenacious proximal convergence type, and the high AC/A ratio type. IXT with high AC/A ratio was defined as an exodeviation for near, more than exodeviation at far distance after prolonged monocular occlusion, and the use of +3.00 DS lenses at near.
- The types of surgery that was performed for IXT was defined as either symmetrical surgery (bilateral lateral rectus recession) or asymmetrical surgery (unilateral lateral rectus recession /medial rectus resection of the nondominant eye).
- Early postoperative CET was defined as initial CET within 10 PD within the first month postoperatively.
- Sensory status: stereopsis was measured by TNO and recorded either present or absent. Suppression was evaluated using the Worth four-dot test; it is either present or absent.
Pearson’s χ2-test was used for statistical analysis, comparing the numerical percentage of the control group (orthotropic group) and CET group. A P value of less than 0.05 was considered significant.
| Results|| |
A total of 120 patients with IXT had undergone surgery to correct their deviation; 15% (18 patients) had CET within the first 6 months postoperatively; 20% had residual angle exotropia; and 65% were orthotropic within the same duration (6 months). [Table 1] shows the demographic data and end results of all patients of IXT postoperatively after 6 months follow-up. An analysis of the predisposing factors as in [Table 2] shows that CET was more common in children of less than 6 years old, which was significant in comparison to the orthotropic group. A P value of preoperative angle of IXT was nonsignificant between both groups. But the P value of the angle of CET was significant between both groups. CET was common in the basic type in 44.4%, then tenacious proximal convergence exotropia type in 16.7%, and high A/CA ratio type in 5.6%, but the tenacious proximal convergence exotropia type was statistically significant in comparison to the control group as in [Table 2]. CET is also common in asymmetrical surgery (recession/resection) than in symmetrical surgery (bilateral lateral rectus recession) P value up to 0.01, 50% of the cases of CET were amblyopic. Also lateral incomitance was found in 27.8% of the CET group, while it was not present in the orthotropic group. No cases with stereopsis were found in the CET group, and nine (50%) cases had suppression.
|Table 1 Demographic data and end results of surgical correction of cases of intermittent exotropia|
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|Table 2 Comparison of risk factors between group of consecutive esotropia and orthotropic group|
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| Discussion|| |
Reported prevalence of persistent CET was varied from 2% up to 20% after correction of exotropia ,,. Many factors have contributed to this . In our study, the prevalence of CET was 15% which was not very low (2.6%) as reported by Cho and Yoo  and Kim et al. . They explained their low prevalence of CET by strict patching therapy preoperatively and early postoperatively, so they decreased the risk of amblyopia. In our study, there was no preoperative patching, but patients who developed CET started patching one month postoperatively. Richard and Parks  explained that the high prevalence of CET (20%) due to many risk factors contributed to this complication. In our study, we found age to be a risk factor where the prevalence increased among children below 6 years old. Jang et al.  found 46% of his patients to be below 7 years; this may be explained by the immaturity of the visual system which was predisposed to the occurrence of CET . Clacke and Noel  found that surgery for IXT at age up to 6 years was significantly associated with the development of CET. There was significant association between postoperative angle of CET and development of persistent CET. By other means all cases had early postoperative esotropia (initial CET) which was preferred by many authors for the success of surgery of IXT. They explained that overcorrection inhibits the recurrence of exotropia and maintained the long-term orthotropia . Recently, it has been known that the initial overcorrection within10–20 PDs was desirable ,. While overcorrection of more than 20 PD was considered a risk factor ,. In our study, all patients of both groups had initial CET that regressed into orthotropia in 65% of cases (orthotropic group), while progressed into persistent consecutive esotropia in 15% of cases, we found the angle to be significant (17±2.2) in comparison to the orthotropic group. According to the type of IXT, our cases of CET were statistically significant in tenacious proximal convergence exotropia; this was in association with Edelman et al.  who found CET was present in 50.0% of the tenacious proximal convergence (pseudodivergence insufficiency) group. Another study reported the type of IXT played as a risk factor for the occurrence of CET, and also mentioned high A/CA ratio type was a risk factor . As regards the type of surgery as a risk factor, we found CET was higher in asymmetric surgery (unilateral recession–resection) than in symmetrical surgery (bilateral lateral rectus recession). That was in association with Keech and Stewart , and Jang et al.  who found that the CET rates were higher in asymmetric surgery especially if it involved more than two muscles (three or four muscles surgery). In the present study, no surgery was performed involving three or more horizontal rectus muscles. Many studies found a significant association between CET and high myopia . Jang et al.  reported a higher incidence of CET among myopic patients than in hyperopic patients. In our study there was no significant findings; this may be due to most of our patients being children, and moderately hyperopic (mean: +3.0±2.0). Progressive CET with lateral incomitance is usually associated with slippage of lateral rectus muscle. This occurred in five cases (27.8%) of our study. Jang et al.  found that the incidence of CET was significantly higher when lateral incomitance was evident, being present in three of the five of his patients. So, lateral incomitance was also considered a great risk factor. Amblyopia is also considered a great risk factor for CET. Jang et al.  have found that the incidence of CET in the amblyopia group was significantly higher than in the nonamblyopia group, this was inconsistent with our findings where 50% of our cases were amblyopes. The terms of binocular visual function associated with the onset of CET was detected by Beneish and Flanders . They reported that a good preoperative fusion and stereopsis resulted in good surgical outcome results. In our study, we found that 50% of the cases had suppression and the other 50% had amblyopia, and there were no cases with stereopsis. It was reported that mature visual system with good binocular function is a predisposing factor toward the success of exotropia surgery; it helps in regression and in the elimination of initial postoperative CET .
| Conclusion|| |
This study concluded that many risk factors may predispose to the development of CET. These factors are less than 6 years old, large postoperative angle of CET, tenacious proximal convergence (pseudodivergence insufficiency) type of IXT, asymmetric surgery (recession–resection procedure), development of lateral incomitance, presence of amblyopia, and suppression.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]