Acta Ophthalmologica 2011
Consecutive exotropia after surgical treatment of childhood esotropia: a 40-year follow-up study Anuradha Ganesh,1 Saeid Pirouznia,2 Shyam S. Ganguly,3 Per Fagerholm4 and Joan Lithander2 1
Department of Ophthalmology, Sultan Qaboos University, Muscat, Oman Department of Ophthalmology, Norra A¨lvsborgs Lasarett, Uddevalla Hospital, Uddevalla, Sweden 3 Department of Epidemiology and Statistics, Sultan Qaboos University, Muscat, Oman 4 Department of Ophthalmology, University of Linko¨ping, Linko¨ping, Sweden 2
ABSTRACT. Purpose: To determine the incidence of consecutive exotropia (XT) following successful surgical correction of childhood esotropia (ET) and identify factors associated with its development. Material and Methods: This is a retrospective study of 85 patients with ET, aged 2–24 , who underwent strabismus surgery by a single surgeon between 1958 and 1969 in Sweden, until they were successfully aligned to ET within 10 prism dioptre, after primary or reoperation(s). The charts of these patients were reviewed, and data regarding age at onset of strabismus, surgery performed and outcome were recorded. The patients were recalled for a complete orthoptic examination in 2001–2003. Results: The incidence of consecutive XT in this cohort was 21% (18 ⁄ 85). Patients who had undergone multiple surgeries had a higher risk of developing consecutive XT compared to those successfully aligned with one surgery (p = 0.00036). Restriction of adduction and convergence postoperatively was associated with a high risk of consecutive XT (p = 0.0437). The incidence of consecutive XT did not vary with the level of visual acuity in the operated eye (p = 0.6428). Age of onset, age at surgery and amount of surgery did not appear to influence the risk for developing consecutive XT (p > 0.05). Conclusion: This 40-year postoperative follow-up of patients with childhood ET who underwent strabismus surgery by a single surgeon in Sweden showed that multiple surgeries and presence of postoperative adduction deficit were the most important factors influencing the incidence of consecutive XT after surgery. Presence of uncorrected amblyopia did not alter the prognosis for longterm development of consecutive XT. Key words: amblyopia – consecutive exotropia – esotropia – strabismus surgery
Acta Ophthalmol. 2011: 89: 691–695 ª 2009 The Authors Journal compilation ª 2009 Acta Ophthalmol
doi: 10.1111/j.1755-3768.2009.01791.x
Introduction Consecutive exotropia (XT) is a manifest XT that develops in a formerly esotropic patient either spontaneously or after optical or surgical treatment for esotropia (ET). It has been reported in 4–27% of patients (Stager et al. 1994; Forrest et al. 2003). Folk et al. (1983) found consecutive XT after all types of corrective ET surgery. Patients with infantile ET (Folk et al. 1983; Stager et al. 1994; Happe & Suleiman 1999), and those with ET associated with high hypermetropia, amblyopia (Folk et al. 1983; Og˘uz et al. 2002), developmental delay (Pickering et al. 1994), multiple previous strabismus surgeries (Ing et al. 1966) and large bimedial recessions (Stager et al. 1994), have been reported to be at a higher risk to develop consecutive XT after surgery. Spontaneous XT occurring in hyperopic esotropic patients without surgery has also been described (Beneish et al. 1981; Swan 1983). The purpose of this study was to identify risk factors for development of consecutive XT in a cohort who underwent surgery for childhood ET and were successfully aligned. Patients operated for ET 32–44 years ago by a single surgeon (Waldemar Nordlo¨w)
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were reviewed (Nordlo¨w 1942, 1953, 1960, 1964), and the effect of age of onset, presence of amblyopia or high hypermetropia, age at surgery, and the presence of immediate postoperative over-corrections on the development of consecutive XT were studied. To our knowledge, there has been no systematic long-term follow-up this many years after surgery for ET.
Material and Methods We identified 131 esotropic patients who were operated on by a single surgeon (Waldemar Nordlo¨w) during 1958–1969 at the Department of Ophthalmology, Va¨nersborgs Hospital, Sweden. Between 2001 and 2003, all 131 patients were invited to attend the eye clinic at Norra A¨lvsborgs Lasarett (NA¨L) for a re-evaluation. Eighty five patients (42 men and 43 women) accepted the invitation. The medical records of these 85 patients were retrospectively reviewed. During this period, the surgical method and dosage for different strabismic angles was constant (Nordlow 1960). All the original typed files were accessible. Much time and effort had been spent to identify the time of onset of strabismus by examining photographs and taking a detailed history. Preoperative evaluation included cycloplegic refraction with atropine, determination of best-corrected visual acuity (for children 4 years or older) and measurement of the preoperative angle of strabismus in primary position for near and distance with correction. Full correction of hypermetropia as determined by atropine retinoscopy had been advised when indicated. No
Table 2. Amount of surgery and correlation with number of patients with consecutive exotropia (XT) (p = 0.649; not significant). Rec = Recession; Res = Resection; MR = medial rectus; LR = lateral rectus; PD = prism dioptre. Angle of esotropia
Surgery dosage
12–25 26–35 36–45 46–55 56–80
Rec Rec Rec Rec Rec
PD PD PD PD PD
MR MR MR MR MR
7–9 mm 3 mm + 4 mm + 5 mm + 6 mm +
Res Res Res Res
LR LR LR LR
3 3 3 3
preoperative prism adaption test had been performed. Occlusion therapy or pleoptic treatment had been instituted in 76 patients below 13 years of age, until the visual acuity was almost equal in both eyes. Patients had been operated at the age of 2 or above (Table 1). The surgical method was as follows: monocular surgery was performed on the nondominant strabismic eye. After making the conjunctival incision over the muscle insertion, a ‘hang-back’ recession of the medial rectus (3–9 mm, depending on the angle of ET; Table 2) was performed using two silk sutures fixed in the muscle insertion. When ET was >25 prism dioptre (PD), a 3- mm resection of the lateral muscle was performed in addition to the medial rectus recession. Reoperations for residual ET and over-corrections were carried out on the fellow eye or the same eye until the eyes were straight or had an ET of 4 years of age. All 18 patients who developed consec-
utive XT had onset of ET before 4 years of age (Fig. 2). However, this result was not statistically significant (p = 0.114). Table 1 shows the relationship between the occurrence of consecutive XT and age at surgery. Sixteen patients were operated at 2 years of age; six of them (37%) developed consecutive XT compared to 12 of 69 (21%) who had surgery after 2 years of age. Although not statistically significant, patients operated at 2 years of age showed a significant trend towards development of the consecutive XT (p < 0.10). The association between amount of recession of the medial rectus and the occurrence of consecutive XT is shown in Table 2. Twenty-eight patients underwent large unilateral recessions of the medial rectus (>6 mm). Seven of them (25%) devel-
Fig. 1. Ocular alignment in 85 patients. 18 ⁄ 85 (21%) patients were detected to have consecutive exotropia.
Fig. 2. Distribution of age at onset of strabismus and correlation with incidence of consecutive exotropia (XT). All 18 patients who developed consecutive XT had onset of esotropia before 48 months.
oped consecutive XT; only three out of 28 patients (11%) with small medial rectus recessions of 3–4 mm combined with 3- mm lateral rectus resection developed consecutive exotropia. However, the influence of amount of surgery on the risk for developing consecutive XT was not statistically significant (p = 0.649). Of 85 patients, 54 had a second operation within the first 2 years. Reoperations (2–5) had been carried out on the fellow eye or the same eye until the eyes were straight or had an ET < 10 PD (Table 3; Nordlow 1960). When reviewed in 2001–2003, of the 18 patients with consecutive XT, 16 were patients who had undergone multiple surgeries. Multiple surgeries were associated with a greater risk for consecutive XT (p = 0.00036) compared to the group who were successfully aligned with one surgery. Patients who had undergone resurgery more than once (16 ⁄ 85) had a higher risk compared to patients who had undergone one resurgery (p = 0.00005). On evaluating the ocular motility, restriction of adduction in the operated eye was detected in 28 ⁄ 85 (33%) patients. Ten of these 28 patients had a manifest XT of 10 PD or more (p = 0.0437). All these patients demonstrated reduced convergence. The association between binocular function after surgery for ET with age of onset of ET was studied. Fifteen patients out of 21 with an onset of ET before 1 year of age had gross binocular function (superposition of the pictures with Bagolini test). Of 12 patients with onset of strabismus between 4 and 10 years of age, only one patient did not have any binocular vision. All the rest had a positive Titmus stereo test (mean 164¢¢). The relationship between the occurrence of consecutive XT and severity of amblyopia is shown in Table 4. The incidence of consecutive XT did not vary with the level of visual acuity (p = 0.6428). High hypermetropia (mean + 7 dioptres; range +6 to +8 D) was present in eight patients; two of these patients developed consecutive XT.
Discussion This study was conducted to determine the incidence of consecutive XT
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Table 3. Relationship between occurrence of consecutive exotropia (XT) and number of strabismus surgeries. Multiple surgeries were associated with a greater risk for consecutive XT compared to the patients successfully aligned with one surgery (p = 0.00036). Number of strabismus surgeries
Number of patients
Consecutive XT (no. and percentage)
1 2 >2
31 38 16
2 (6) 6 (21) 10 (62)
Table 4. Relationship between the occurrence of consecutive exotropia (XT) and amblyopia. The incidence of consecutive XT did not vary with the level of visual acuity (p = 0.6428). Visual acuity (VA) of study population in 2001–2003 Deep amblyopia VA = FC ) 0.3 Moderate vision VA = 0.4–0.8 Good vision VA = 0.9–1.0
Total number 4
1 (25)
25
6 (24)
56
11 (20)
following initial successful surgical alignment of childhood ET in a patient cohort who had undergone strabismus surgery by a single surgeon in Sweden 40 years ago and factors responsible for its development. Such a retrospective study was possible to conduct because of a very efficient population registry in Sweden. The 21% incidence of consecutive XT in our study group is high when compared to other figures such as the 4–12% figure quoted by Forrest et al. (2003). We attribute this to the longer follow-up period in our study. It is well known that the incidence of consecutive XT tends to increase with time (Yazawa 1981; Kerkhof & Houtman 1992; Happe & Suleiman 1999; Og˘uz et al. 2002; Donaldson et al. 2004). Another factor that might have been responsible is the surgical technique employed in some patients (large recessions of >6 mm). The group with the least consecutive XT (3 ⁄ 28; 11%) appeared to be patients who underwent small recessions of 3–4 mm with 3 -mm resection of lateral rectus, surgical numbers more akin to what is currently practised. However, when analysing the influence of amount of surgery to the incidence of consecutive XT in our study, the correlation was not statistically significant. Further, it must be remembered that all patients were operated to achieve initial alignment to within 10 PD of ET. On comparing the incidence of consecutive XT between patients with
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Number of patients with consecutive exotropia (%)
onset of strabismus before and after 4 years of age, a difference was noted between the two groups with a lower incidence in children with late onset strabismus. We attribute this to the better binocular function in the older group. The relationship between age of onset of ET and postoperative binocular function and thereby the stability of postoperative alignment was evaluated, and it was observed that patients with an onset of strabismus before 1 year of age had no binocularity (6 ⁄ 21) or only had gross binocular function (15 ⁄ 21) when compared with patients with strabismus of late onset, where 11 ⁄ 12 patients had a mean stereo acuity of 164¢¢. Better binocular function translates into better postoperative stability and less consecutive XT. Other studies have reported that treatment protocols designed to optimize stereoacuity outcomes promote long-term stability of alignment after surgery (Maruo et al. 2000; Birch et al. 2004; Lennerstrand 2007). When analysing the effect of age at surgery on incidence of consecutive XT, it was seen that patients who had undergone early surgery (at the age of 2 years) had a higher incidence of the complication. Proponents of early surgery for ET suggest that improved binocular status in patients operated early translates into better outcomes; however, these authors refer to surgeries performed before the age of 2 (Simonz et al. 2005), unlike that performed by Nordlow in our cohort. In
contrast to previous studies (Folk et al. 1983; Og˘uz et al. 2002), amblyopia did not increase the risk for consecutive XT in our study. Although it appeared that patients with residual amblyopia had a slightly higher risk of developing consecutive XT (Table 4), the difference between groups was not statistically significant. Fifty-four patients underwent more than one surgery to be successfully aligned. Sixteen of these patients had developed an overcorrection after first surgery. A highly significant correlation was observed between number of strabismus surgeries and incidence of consecutive XT with the incidence increasing with increasing number of surgeries. Previous reports have indicated that multiple surgeries are associated with a greater risk for consecutive XT (Ing et al. 1966; Kerkhof & Houtman 1992). Twenty-eight out of the 85 patients (33%) exhibited a postoperative limitation of adduction. Ten of these 28 patients (36%) with adduction defect developed consecutive XT, and the correlation was statistically significant. Og˘uz et al. (2002)had also reported that postoperative limitation of adduction increased the risk for consecutive XT. It can be argued that limitation of adduction may cause convergence impairment, that may in turn lead to instability of alignment and late exotropic drift (Forrest et al. 2003). Two of eight patients with high hypermetropia (25%) developed consecutive XT. Patients with hypermetropia have been reported to develop consecutive XT even without surgery (Beneish et al. 1981; Swan 1983). Hypermetropic patients with diminished accommodative convergence ability have a higher risk of developing XT during long-term follow-up (Berk et al. 2004). This is particularly true of hypermetropic patients with amblyopia (Swan 1983). In conclusion, our study shows that multiple surgeries and presence of postoperative limitation of adduction are strongly correlated with a high risk of consecutive XT. Patients with therapy-resistant amblyopia did not show a higher risk of consecutive XT in our study. Children with onset of strabismus below the age of 4 , early surgery at 2 years of age and in whom large recessions >6 mm had been performed showed a trend towards hav-
Acta Ophthalmologica 2011
ing a higher risk for developing consecutive XT, but the correlations were not statistically significant.
Acknowledgements This work was presented in part at the XXXV Nordic Congress of Ophthalmology in Tampere, Finland, 2002, the 9th meeting of the Child Vision Research Society, 12–14 June 2003, Go¨teborg, Sweden, the XI Nordic meeting for Paediatric Ophthalmology in Uppsala, Sweden, 2003, and the XIV Annual Iranian Ophthalmology Meeting in Tehran, 2003.
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Received on December 5th, 2008. Accepted on October 7th, 2009. Correspondence: Dr Anuradha Ganesh Department of Ophthalmology Sultan Qaboos University Hospital 123 Al Khod ⁄ Muscat Oman Tel: +00968 2414 3516 Fax: +00968 2414 4560 Email:
[email protected]
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