Introduction

Intermittent exotropia is the most common type of strabismus in Korean children and often requires surgical treatment to achieve proper ocular alignment [1,2]. Pediatric patients with intermittent exotropia tend to have coexisting eyelid abnormalities that require surgery. Eyelid and exotropia surgeries are typically performed under general anesthesia. The simultaneous performance of these procedures can reduce the number of anesthetic exposures and shorten the overall recovery period. However, there are concerns that the combination of these surgeries may affect exotropia outcomes.

Previous studies investigated the clinical factors associated with favorable outcomes in intermittent exotropia and examined the feasibility of combining eyelid and strabismus surgeries [3-5]. However, most of these studies either included mixed types of strabismus or did not directly assess the surgical outcomes of simultaneous strabismus surgeries. Thus, this study aimed to compare the surgical outcomes of pediatric patients with intermittent exotropia who underwent simultaneous eyelid and exotropia surgery and those who underwent exotropia surgery alone.

Methods

Ethics statement: This study was approved by the Institutional Review Board (IRB) of Yeungnam University Hospital (IRB No: 2024-11-015). The requirement for informed consent was waived because of the retrospective study design and the use of anonymized patient data.

This study was a retrospective review of the medical records of pediatric patients (<18 years old) who underwent surgery for intermittent exotropia between September 2015 and February 2024. Patients were included if they had basic-type exotropia with a difference of ≤10 prism diopters (PD) between their near and distance deviation angles and underwent simultaneous eyelid and exotropia surgery.

We excluded patients with other types of strabismus such as oblique muscle dysfunction, dissociated vertical deviation, A-V patterns, or nystagmus. Patients with a history of intraocular surgery, unilateral amblyopia, or neurological impairments such as cerebral palsy were excluded from the analysis.

1. Preoperative evaluation and surgical treatment

The onset of exotropia was determined based on reports from the patients or their parents. The degree of deviation was measured using the prism and alternate cover test at 6 m (distance fixation) and 33 cm (near fixation). To measure maximum exodeviation, we provided all patients with an occlusive patch during their initial visit and informed them that the non-dominant eye would be occluded for 1 hour at the subsequent visit.

The control level was quantified using the LACTOSE (Look And Cover, then Ten seconds of Observation Scale for Exotropia) control scoring system [6]. This scale combines a 5-point scale for both distance and near evaluations (0–4 for each), resulting in a total score ranging from 0 to 8 points. Higher scores indicate poorer control, whereas lower scores indicate better control. Stereoacuity measurements were performed using Lang I (Lang-Stereotest AG, Küsnacht, Switzerland) and the Stereo Fly test (Stereo Optical Co., Chicago, IL, USA) in patients who cooperated and completed the test. A slit lamp examination was conducted to identify corneal or eyelid issues. Patients with eyelid abnormalities were referred to an oculoplasty specialist to determine the appropriate surgical plan. All surgeries were performed under general anesthesia. Eyelid surgery was performed prior to exotropia surgery. Each surgical procedure was performed by the same surgeon (i.e., eyelid surgery by JHS and exotropia surgery by WJK). Conventional bilateral lateral rectus muscle recession or unilateral lateral rectus muscle recession and medial rectus muscle resection for exotropia were performed using the surgical dosage method at our clinic based on the patient’s deviation angle measured the day before surgery (Table 1). Immediate postoperative deviation was defined as the angle measured on the day of surgery or 1 day after surgery. Patients were followed up at 1, 3, 6, and 12 months postoperatively, and every 6 months thereafter. Only patients with at least 3 months of postoperative follow-up were included in the final analysis.

A favorable or successful surgical outcome was defined as a residual ocular deviation ≤10 PD for exotropia and ≤4 PD for esotropia at both distance and near fixation in the primary position. Recurrence was defined as exotropia >10 PD at any point postoperatively, at distance or near deviation.

2. Statistical analysis

Statistical analyses were performed using IBM SPSS for Windows ver. 20.0 (IBM Corp., Armonk, NY, USA). To compare the surgical outcomes between simultaneous eyelid and exotropia surgery and exotropia surgery alone with similar distributions of certain characteristics, a matched exotropia surgery alone dataset was generated using a propensity score matching method from the entire list of patients who underwent exotropia surgery alone. For propensity score matching, sex, exotropia onset, age at surgery, preoperative ocular deviation, stereo test results, and refractive errors were selected as the covariates. After matching, a 1:3 matched dataset was created. Differences between the two groups were evaluated using unpaired t-tests and chi-square tests. The cumulative probabilities of success were assessed using Kaplan–Meier life-table analysis. Survival rates were compared between the two groups using log-rank tests. The association between clinical factors and surgical outcomes in patients who underwent simultaneous eyelid and exotropia surgery was evaluated using logistic regression analysis. Statistical significance was set at a p-value of <0.05

Results

Thirty-one patients who underwent simultaneous eyelid and exotropia surgery and 87 patients who underwent exotropia surgery alone were analyzed. Basic patient characteristics are presented in Table 2. Clinical factors, including sex, exotropia onset, ocular deviation, control scores, spherical equivalent refractive errors, age at surgery, and stereoacuity test results, did not differ significantly between the two groups (all p>0.05). Table 3 shows the types of eyelid and exotropia surgeries performed. The number of types of exotropia surgery did not differ between the two groups. Bilateral repair of lower lid epiblepharon was the most common eyelid surgery performed in conjunction with exotropia surgery (27/31, 87.1%).

1. Surgical outcomes of simultaneous eyelid and exotropia surgery

Simultaneous eyelid and exotropia surgery was performed without any significant complications. The immediate postoperative ocular deviation was −3.6±2.3 PD at distance fixation and 0.3±2.8 PD at near fixation in patients who underwent simultaneous eyelid and exotropia surgery, in which negative and positive numbers indicate esodeviation and exodeviation, respectively. The patients who underwent exotropia surgery alone showed −4.4±2.2 PD at distance fixation and 0.3±2.8 PD at near fixation immediately after surgery, indicating no significant difference between the two groups (p=0.070 at distance fixation; p=0.153 at near fixation). The mean postoperative follow-up was 26.8 months (range, 3–73 months) in patients who underwent simultaneous eyelid and exotropia surgery and 22.0 months (range, 3–61 months) in patients who underwent exotropia surgery alone (p=0.133). The Kaplan–Meier analysis with recurrence as the event indicated that the cumulative probabilities of success rates in patients who underwent simultaneous eyelid and exotropia surgery were 89.0%, 84.8%, 77.1%, and 51.4% at 1, 2, 3, and 4 years after surgery, respectively. In contrast, the rates of patients who underwent exotropia surgery alone were 83.5%, 78.6%, 69.1%, and 45.2%, respectively. Surgical outcomes did not significantly differ between the two groups, as analyzed using the log-rank test (p=0.291, Fig. 1). In patients who underwent simultaneous eyelid and exotropia surgery, clinical factors including the type of eyelid surgery, sex, exotropia onset, ocular deviation, control scores, spherical equivalent refractive errors, age at surgery, and stereoacuity test results were not significantly associated with favorable surgical outcomes (all p>0.05).

Discussion

The surgical outcomes of exotropia in pediatric patients who underwent simultaneous eyelid and exotropia surgery did not differ significantly from those of patients who underwent exotropia surgery alone. Moreover, the type of eyelid surgery was not associated with surgical outcomes in patients who underwent simultaneous eyelid and exotropia surgery.

Intermittent exotropia is the most common type of strabismus in Korean children [1,2]. Surgical treatment usually involves improving ocular alignment in pediatric patients with intermittent exotropia. Eyelid conditions, such as epiblepharon, epicanthus, and ptosis, are also commonly observed in Asian children [7,8]. General anesthesia is required for most pediatric patients undergoing eyelid or exotropia surgery. Performing eyelid and exotropia surgeries simultaneously can reduce the number of surgical and general anesthetic procedures required, lower total medical costs, and accelerate postoperative recovery [3,9]. However, the potential effectiveness of simultaneous eyelid and exotropia surgery for improving the surgical outcomes of intermittent exotropia has not yet been investigated.

Previous studies evaluated the surgical outcomes of simultaneous strabismus and eyelid surgery [3-5]. They included various types of strabismus but did not compare the surgical outcomes of strabismus [3-5]. Exotropia frequently recurs after surgical treatment. Previous studies have assessed the associations between clinical factors and favorable surgical outcomes in patients with intermittent exotropia [2,10,11]. Although simultaneous eyelid and exotropia surgeries are commonly performed in clinical practice, no study has directly compared the surgical outcomes of exotropia in patients who underwent both procedures. In the present study, we evaluated only patients with intermittent exotropia, which is the most common type of strabismus, and compared the surgical outcomes between those who underwent simultaneous eyelid and exotropia surgery and those who underwent exotropia surgery alone.

Based on our findings, no significant differences in the surgical outcomes of intermittent exotropia were observed between patients who underwent simultaneous eyelid and exotropia surgery and those who underwent exotropia surgery alone. Despite concerns that combining such procedures may increase intraoperative manipulation, reduce surgical visibility, or exacerbate postoperative swelling, our results suggest that these factors do not significantly affect the surgical outcomes of exotropia in pediatric patients. Increased tissue handling during combined procedures can theoretically contribute to transient postoperative inflammation or discomfort, which may interfere with the postoperative reestablishment of binocular function [12]. However, our findings suggest that these effects are clinically minimal and do not compromise surgical success.

These results are consistent with those of previous reports, confirming the feasibility and safety of simultaneous eyelid and strabismus surgery. Revere et al. [4] reported no significant difference in outcomes between simultaneous and sequential ptosis and strabismus surgeries in children, suggesting that combined surgery does not adversely affect ocular alignment or complication rates. Similarly, McCracken et al. [3] reported favorable outcomes in patients who underwent concurrent eyelid and horizontal strabismus procedures. The present study builds on this evidence by focusing exclusively on patients with intermittent exotropia. Based on these findings, simultaneous eyelid and exotropia surgery can be considered a safe and effective approach, providing the advantage of reduced anesthesia exposure without compromising surgical efficacy.

Simultaneous eyelid and exotropia surgery can reduce repeated exposure to general anesthesia and mitigate parental concerns regarding its potential risks. A major consideration in pediatric surgical planning is the risk associated with general anesthesia, which is often a source of significant concern for parents [13]. Therefore, performing eyelid and exotropia surgeries in a single session helps reduce cumulative exposure to general anesthesia, making it beneficial in pediatric patients. Furthermore, previous studies have suggested that a short duration of anesthesia exposure, such as in typical strabismus surgeries, is safer than a long duration of repetitive exposures [14,15].

Clinical factors, including the type of eyelid surgery, were not associated with surgical outcomes in patients who underwent simultaneous eyelid and exotropia surgery. Although the surgical outcomes were comparable to those of exotropia surgery alone, simultaneous procedures may result in increased postoperative swelling, which could temporarily affect patient recovery. Clinicians should be aware of this possibility and counsel parents preoperatively regarding the expected postoperative changes. Moreover, this study included only patients who underwent horizontal rectus muscle strabismus surgery. McCracken et al. [3] reported that simultaneous eyelid and strabismus surgery may not be advisable in cases involving vertical rectus muscle procedures because it may result in eyelid position alterations. These considerations emphasize the importance of careful patient selection when planning simultaneous surgical correction of exotropia and eyelid abnormalities to optimize safety and clinical outcomes.

This study had several limitations. First, it included only patients who underwent eyelid surgery followed by exotropia surgery. Patients in whom exotropia surgery was performed before eyelid surgery were excluded from the study. Horizontal extraocular muscle surgery can change the contour of the eyelid fissure, which can affect surgical outcomes [16]. Moreover, this study did not evaluate the potential influence of the surgical sequence, specifically, whether exotropia or eyelid surgery was performed first. Second, this study included only pediatric patients with intermittent exotropia. Surgical outcomes of adult patients who underwent simultaneous eyelid and exotropia surgery were not analyzed in this study. The clinical characteristics and surgical outcomes of intermittent exotropia may differ between pediatric and adult patients [17]. Third, most patients in the simultaneous surgery group underwent bilateral repair of lower lid epiblepharon, which is unlikely to have directly influenced ocular alignment. However, perioperative factors such as surgical tissue handling, anesthesia duration, and postoperative swelling could theoretically affect visual function or the recovery process after strabismus surgery. Our findings, showing no significant differences in surgical outcomes between the two groups, suggest that even when such potential concerns are considered, simultaneous eyelid and exotropia surgery can be safely performed without compromising alignment results.

Article information

Conflicts of interest

Won Jae Kim has been an Editorial Board Member of Journal of Yeungnam Medical Science since 2021. He was not involved in the review process of this manuscript. There are no other conflicts of interest to declare.

Funding

None.

Author contributions

Conceptualization: JHS, WJK; Data curation: all authors; Formal analysis, Visualization, Supervision, Validation: WJK; Methodology: JL; Investigation, Resources: JHS; Writing-original draft: JHS, WJK; Writing-review & editing: JL, WJK.

Fig. 1.

Comparison of the Kaplan–Meier curves of the surgical outcomes between simultaneous eyelid and exotropia surgery and exotropia surgery alone. The recurrence-free curve does not differ between the groups (p=0.291, log-rank test). The cumulative probabilities of success considering recurrence as the event in patients who underwent simultaneous eyelid and exotropia surgery are 89.0%, 84.8%, 77.1%, and 51.4% at 1, 2, 3, and 4 years after surgery, respectively. In contrast, the probabilities of patients who underwent exotropia surgery alone are 83.5%, 78.6%, 69.1%, and 45.2%, respectively.

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References

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