Ptosis repair is challenging for oculoplastic surgeons. Repair of congenital ptosis is additionally challenging because levator muscle function that influences the choice of technique must be roughly estimated in small children, general anesthesia precludes accurate intraoperative assessment, and monitoring of postoperative corneal status is difficult. Timing of surgery for congenital ptosis is an often-debated issue. In some patients, the visual axis is obstructed making it necessary to pursue surgery.1–3 Alternatively, a significant chin lift adopted to clear the visual axis may be a relative indication for early surgery. In many patients, however, the visual axis is clear, and the determinants of early surgery are less certain. One frequently used criterion is refractive error, particularly anisometropia or increasing astigmatism in the setting of amblyopia.2,3 Several studies have shown a higher prevalence of preoperative astigmatism and corneal irregularities in children with ptosis4–10; however, lessening of these factors following ptosis surgery has not been convincingly demonstrated.11–16 Nevertheless, recent reports in both the oculoplastic and pediatric ophthalmology literature continue to cite anisometropia as an indication for early intervention. For example, SooHoo et al.2 in 2014 stated, “surgical repair of congenital ptosis is indicated when the upper eyelid…induces astigmatism that is amblyogenic.” Marenco et al.3 in 2017 asserted, “[W]hen the upper eyelid…induces amblyogenic astigmatism, surgical intervention is mandatory.”
For the oculoplastic surgeon, later surgery (≥4 years of age) for congenital ptosis is beneficial for several reasons.6 First, it allows for more accurate estimates of levator function to aid in appropriate presurgical planning. In addition, there is a decreased risk of postoperative exposure keratopathy as children are better able to cooperate with forced closure exercises and the corneal status can be more accurately monitored. Finally, there is mounting evidence that exposure to general anesthesia at a young age has associated risks.17–19 If surgery can be deferred to an older age without impacting visual status, patients are likely to benefit from both surgical and systemic/developmental standpoints.
The authors study investigates the change in refractive error and amblyopia in children undergoing ptosis surgery to better inform decisions regarding surgical timing.
Following institutional review board approval, a retrospective chart review was performed on pediatric patients who underwent surgery for congenital ptosis between May 2002 and May 2017. The following current procedural terminology codes were used to identify patients: 67901 (frontalis sling), 67904 (external levator advancement), and 67908 (conjunctival Müller muscle resection). All data that were collected was stored in a Health Insurance Portability and Accountability Act-compliant manner. The study adhered to the tenets of the Declaration of Helsinki as amended in 2013.
Medical record review generated a total of 184 patients who underwent ptosis surgery during the study period, and 56 were able to be included in the study. Of the 128 excluded patients, 56 had no postoperative refractive data available, 41 had pediatric ophthalmology care outside the Medical College of Wisconsin, 19 were surgically undercorrected (postoperative margin reflex distance <220), 9 had ptosis of other etiology (trauma, myasthenia gravis, or eyelid mass), and 3 had conditions that precluded refraction (anophthalmia or microphthalmia).
Of the 56 patients included in the study, 15 had bilateral involvement, for a total of 71 ptotic eyes. In unilateral cases, the nonoperative eye was used as an age-matched control. Data collected included age, gender, race, affected eye, refractive error, alignment, and amblyopia status. All surgeries were performed by the oculoplastic surgeons at the Medical College of Wisconsin. All refractions were performed by pediatric ophthalmologists at the Children’s Hospital of Wisconsin.
Data were analyzed using GraphPad Prism 7.04 software. Descriptive statistics were performed to determine the demographics of the patients who present with congenital ptosis, as well as the baseline clinical characteristics of those patients. Comparisons between groups were performed using unpaired t tests. Preoperative and postoperative data were compared amongst groups using paired t tests.
During the study period, 184 children underwent surgery for congenital ptosis at the Medical College of Wisconsin. Complete preoperative and postoperative refractive data were available for 56 patients. All 112 eyes were analyzed, with the nonoperative eyes used as age-matched controls in the unilateral cases. There were 15 bilateral cases, resulting in 71 ptosis eyes and 41 control eyes.
The average age of the patients at presentation to pediatric ophthalmology was 2.7 years old (range 0.1–14.5). Average age at the time of surgery was 5.1 years old (range 0.1–15.5). All types of ptosis surgery were included in this study: frontalis sling in 48 eyes (67.6%), external levator advancement with modified tarsal resection in 11 eyes (15.5%), external levator advancement in 9 eyes (12.7%), and conjunctival Müller muscle resection in 3 eyes (4.2%). Average time between surgery and final refraction was 34 months (range 3–106). Average total follow up was 66 months (range 13–157). Further baseline characteristics of the patients are outlined in Table 1.
At the pediatric ophthalmic examination immediately preceding surgery, 32 of the 56 patients (57.1%) had strabismus, amblyopia, and/or anisometropia. The average spherical equivalent was 1.64 D ± 0.42 in the ptosis eyes and 1.00 D ± 0.35 in the control eyes in unilateral cases. These values were not statistically significantly different (p = 0.3013). Astigmatism (defined as any amount of cylinder) was present in 42 (59.2%) of the ptosis eyes compared with 17 (41.5%) of the control eyes. The average magnitude of astigmatism was 0.77 D ± 0.12 in the ptosis eyes and 0.37 D ± 0.10 in the control eyes. This was a statistically significant difference (p = 0.0218).
Preoperative refractive data were compared with postoperative refractive data (Table 2). The mean refractive change in the ptosis eyes was a 0.82 D decrease in spherical equivalent (p = 0.1920) and a 0.40 D increase in cylinder (p = 0.0255). The mean refractive change in the control eyes was a 0.41 D decrease in spherical equivalent (p = 0.4124) and a 0.30 D increase in cylinder (p = 0.1199). No association was found between the amount of preoperative ptosis or the surgery performed and the amount of postoperative refractive change.
The preoperative and postoperative data were compared with the patients divided into those <4 years of age and ≥4 years of age (Table 3). The mean refractive change in the ptosis eyes in patients <4 years old was a 0.94 D decrease in spherical equivalent (p = 0.1938) and a 0.10 D increase in cylinder (p = 0.6599). The mean refractive change in the control eyes in patient <4 years old was a 0.88 D decrease in spherical equivalent (p = 0.4353) and a 0.12 D increase in cylinder (p = 0.5711). The mean refractive change in the ptosis eyes in patients ≥4 years old was a 0.73 D decrease in spherical equivalent (p = 0.4341) and a 0.61 D increase in cylinder (p = 0.0156). The mean refractive change in the control eyes in patient ≥4 years old was a 0.20 D decrease in spherical equivalent (p = 0.7167) and a 0.39 D increase in cylinder (p = 0.1467).
Attention was also directed to changes in the axis of astigmatism (Table 4). In the eyes with operated ptosis, there was a statistically significant increase in the number of patients with astigmatism postoperatively compared with preoperatively (p = 0.0424). This was due mostly to increases in “with the rule” (6 eyes) and “against the rule” (6 eyes) astigmatism not oblique astigmatism (2 eyes). No statistically significant difference in the types of astigmatism was noted in the control eyes over the preoperative to postoperative interval (p = 0.1429).
At the final examination, amblyopia was present in 21 patients (37.5%), and anisometropia was present in 18 patients (32.1%). Neither of these values was statistically significantly different than the preoperative values (amblyopia, p = 0.1089; anisometropia, p = 0.7843).
Congenital ptosis is commonly treated by oculoplastic surgeons. One of the most critical components in the care of these patients is determining when surgical correction should be performed. Deprivational amblyopia is a clear indication for surgery.1–3 Anisometropic amblyopia is also a classically cited indication for performing ptosis surgery at a younger age—as recently reiterated in recommendations by SooHoo et al.2 and Marenco et al.3
The justification for surgical correction of ptosis to treat or prevent anisometropic amblyopia is based on the assumption that astigmatism is induced by mechanical forces exerted by the ptotic eyelid, similar to astigmatism induced by a large chalazion or hemangioma.21–23 In fact, studies have shown abnormal corneal topography in patients with ptosis.24–26 Theoretically, lifting the ptotic eyelid should alleviate this mechanical force and correct the astigmatism.
In reality, several studies have shown increased astigmatism following ptosis surgery in the pediatric population. In 1980, Merriam et al.11 published a retrospective case study of 65 patients. Of the 37 patients with postoperative refractive data, 10 patients showed an increase in astigmatism. In 4 of these patients, amblyopia developed as a consequence of their newly acquired astigmatism.
In 1992, Cadera et al.12 performed a retrospective chart review on 62 patients (88 eyes, 58 eyes with complete refractive data) that showed a statistically significant difference in refractive error change between the operative group and control eyes (normal eyes in unilateral cases). The operative group showed an average increase in cylinder of 0.30 D while the control group showed an average decrease in cylinder of 0.15 D (p < 0.005). They went on to explore the connection between age and the change in cylinder by repeating the statistical analysis with the patients broken down into 2 groups (<4 years old and ≥4 years old). The younger group was noted to have an average decrease in cylinder of 0.20 D while the older group was noted to have an average increase in cylinder of 0.50 D. They used these data to advocate for surgery at a younger age in patients with marked astigmatism. However, it is important to note that the changes based on age were not statistically significant due to the small number of patients when separated into age groups (19 patients <4 years old and 39 patients ≥4 years old).
In 2001, Klimek et al.13 performed a chart review on 28 patients who underwent unilateral levator resection for repair of congenital ptosis. They found a statistically significant increase in cylinder following surgery (average 0.83 D, p = 0.002). They used the nonoperative eye as an age-matched control and did not find any significant increase in cylinder in this group (average 0.36 D, p = 0.422).
In 2016, Paik et al.16 presented the most recent study on this topic. They specifically focused on Asian eyelids as no prior studies had focused on this population and there are known racial differences in eyelid anatomy. Interestingly, they did not find any significant change in the magnitude of astigmatism following surgery, but they did find a statistically significant increase in the amount of oblique astigmatism in the postoperative eyes. This change to oblique astigmatism is clinically significant in that it has been shown that treatment of amblyopia is more difficult in patients with oblique astigmatism compared with with the rule/against the rule astigmatism.27 The authors study did not show an increase in oblique astigmatism following ptosis surgery, but this may be attributed to the authors patient population which only included 6 Asian patients (10.7%).
In addition to the studies above that show worsening of refractive error following ptosis surgery, there are several other studies in the literature that either show no change or only transient changes to refractive error.10,14,15 Several of these studies have included ancillary tests to look at the structure of the cornea and have not shown any lasting effects of ptosis surgery on the shape of the cornea.14,28–30
Based on previous literature and the data from the authors study, there is no convincing evidence that current or threatened anisometropic amblyopia should be the sole indication for ptosis surgery at a younger age. While the article by Cadera et al.12 shows a trend toward lessened astigmatism following ptosis surgery in patients under 4 years of age, this is not a statistically significant result. The authors data did not support this and actually showed a nonstatistically significant trend toward worsening of astigmatism after ptosis surgery in this age group. All other articles (including the aggregate data in the Cadera et al.12 article and the authors aggregate data) show either a worsening of astigmatism or no significant change in refractive error. As there is at best no significant change in refractive error, the patients are at the same risk for anisometropic amblyopia following surgery as they are prior to surgery. With no clear advantage regarding improvement in refractive error, it would likely serve these patients best to have surgery later in life when they can better participate in examination and possibly have a lower risk of anesthesia-related complications. Some may argue that lifting the eyelid could result in better acceptance of patching by patients; however, there is no evidence that this makes any difference when there is not obstruction of the visual axis.
The authors study reports on the largest number of eyes with complete preoperative and postoperative refractive data. Most importantly, it adds to the literature a discussion of surgical timing based on the changes in refractive error following ptosis surgery, highlighting that anisometropic amblyopia alone should not be an indication for early surgical repair of ptosis. Like the majority of studies on this topic in the literature, it is a retrospective chart review and comes with inherent limitations. There is only 1 prospective study in the literature on this topic by Kumar et al.14 While this is a well-designed study that followed patients at regular intervals and measured astigmatism with multiple modalities, it had a small sample size and did not include patients under the age of 4. Repeating a similar study with a larger sample sizing including patients under of the age of 4 would be helpful to definitively determine if there is any indication for surgical repair of ptosis in patients with anisometropic amblyopia.
The author data analysis also emphasizes the importance of pediatric ophthalmology follow up. Anisometropia and amblyopia persist in many patients postoperatively and even develop anew in others. This should be emphasized with parents who may assume that all of their child’s vision concerns have been addressed by a successful ptosis surgery. It is notable that 56 of the author original 184 patients (30.4%) were excluded because there was no follow up with pediatric ophthalmology, and thus no postoperative refractive data were obtained. Despite parents always being advised to follow up with pediatric ophthalmology (and in most cases having appointments scheduled), many patients were lost to follow up. This was also noted in other retrospective studies. The percentages of patients excluded because of missing refractive data were: Merriam et al.,11 24.5%; Cadera et al.,12 34.1%; Klimek et al.,13 60%; Paik et al.,16 64.7%; and Byard et al.,15 69.8%. Appropriate follow up for these patients should be stressed to avoid treatable vision loss from amblyopia.
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