The strabismus seen in high myopia associated with a large axial length is typically characterized by a progressive esotropia and hypotropia. In advanced stages, the restricted ocular motility progresses such that abduction and/or elevation are not possible; this stage has been termed convergent or myopic strabismus fixus. Magnetic resonance imaging (MRI) studies have shown the inferior displacement of the lateral rectus muscle and nasal displacement of the superior rectus muscle in patients with heavy eye syndrome.1,2 Furthermore, this is associated with superotemporal displacement of the globe out of the muscle cone, the degree of which closely corresponded to the degree of limitation in abduction and elevation.3
Retro-equatorial uniting of the muscle bellies of the superior and lateral rectus muscles has been shown to adequately restore the ocular motility abnormality and globe displacement in heavy eye syndrome.3,4 This may be performed alone or in combination with a medial rectus recession, either at the time of surgery or as a second-stage procedure. Persistent esotropia following surgery is reported with medial rectus contracture in long-standing cases.5,6 Some of the larger series reported show a high incidence of medial rectus recession at the time of muscle union surgery, ranging from 74% to 100%.3,7,8 We report our experience of isolated retro-equatorial muscle union surgery for heavy eye syndrome.
Patients and Methods
This was a retrospective review of patients who underwent muscle union surgery for heavy eye syndrome over a 9-year period. The axial length, refractive error, symptoms, and demographic data were recorded for each patient. Measurements of the strabismus in primary position were made using the prism cover test or prism reflex test. The range of ocular motility limitation was graded from 0 to -5, with grade 0 indicating no limitation, grade -4 indicating inability to cross the midline, and grade -5 indicating cases where the eye was adducted and could not be moved to the midline. Displacement of the lateral and superior recti was evaluated with MRI using coronal images as suggested by Yokoyama.4
Patients underwent surgery after giving informed consent for muscle union surgery. The lateral rectus and superior rectus muscles were exposed and isolated via a limbal periotomy. Half of each muscle belly was approximated and sutured together using 5-0 non-absorbable sutures at 14 mm posterior to their insertion. Patients were reviewed at 1, 3, and 6 months postoperatively. The angle of deviation was measured in the primary position and the range of ocular motility limitation recorded at each visit.
The outcome was considered successful if the patient's deviation was within 10 PD of orthotropia.
There were 26 patients in total and 29 procedures performed. Two patients had a bilateral procedure and 1 patient had loop myopexy surgery on one eye followed by the other eye at a later date.
The mean age was 53 years (range: 7 to 82 years). There were 14 right-sided and 15 left-sided procedures performed. The mean axial length was 31.8 mm (standard deviation: 2.8). Eleven of the 26 patients presented with diplopia and 15 with psychosocial concerns regarding the appearance of the eye.
The mean preoperative esodeviation was 29.75 ± 24.03 PD, which improved to 13.27 ± 16.32 PD. The mean preoperative hypotropia was 13.4 ± 10.4 PD, which improved to 3.9 ± 4.6 PD. The mean change in esotropia was 16.1 ± 14.6 PD. The mean preoperative limitation in abduction was −2.0 ± 1.4 and improved to −1.2 ± 1.2 after surgery. The mean preoperative limitation in elevation was −1.3 ± 1.3, which improved to −0.5 ± 0.6 after surgery. Twenty-two eyes had marked limitation in abduction, with 6 having limitation of -3 or more. Fifteen had limitation in elevation, with 5 patients having limitation of -3 or more.
There were 7 patients and 8 eyes in total that went on to have a second-stage medial rectus recession. The mean esotropia in this subgroup was greater than the mean for the entire study group at 46.4 ± 28.1 PD. Following muscle union, the mean esotropia reduced to 31.4 ± 14.2 PD and improved to 15 ± 7.3 PD after second-stage medial rectus recession. The mean preoperative esotropia in the 19 patients who underwent muscle union surgery alone was 21.2 ± 16.3 PD, which improved to 5.5 ± 9.1 PD after surgery.
Figure 1 shows the preoperative and postoperative angles of esotropia and the preoperative limitation in abduction for each patient. Figure 2 shows the preoperative and postoperative limitation in abduction for each patient.
Bar chart showing preoperative and postoperative change in the angle of esotropia (ET) and the preoperative limitation in abduction for each patient. *indicates those patients who underwent a second-stage medial rectus recession. PD = prism diopters
Bar chart showing the preoperative and postoperative limitation in abduction in each patient. *indicates those patients who underwent a second-stage medial rectus recession.
All patients had an improvement in their initial presenting symptoms and there were no complications.
Three of 7 patients who required a second-stage procedure had a -4 or more limitation in abduction preoperatively. One of these patients had bilateral heavy eye syndrome with an esotropia measuring 80 PD. Of the 19 patients who did not have a second-stage procedure, 17 had a postoperative esodeviation within 10 PD of orthophoria and 2 had a postoperative deviation in excess of 10 PD. These were patients 24 and 26, who had postoperative esodeviations measuring 20 and 30 PD, respectively. Both had a significant improvement from their initial deviation and were offered further surgery; however, both declined.
The superotemporal displacement of the posterior globe in heavy eye syndrome has been elucidated by MRI studies and the degree of displacement corresponds to the severity of strabismus fixus.2,3 It is postulated that the intermuscular membrane in the superotemporal quadrant is a vulnerable area for this to occur due to the lack of extraocular muscle support. Furthermore, Rutar and Demer suggested that loss of connective tissue elasticity, particularly between the lateral rectus and superior rectus muscles, is a key component to the progressive nature of this condition.9
Muscle union surgery has been shown to restore the globe to its original position, thereby reducing the angle of displacement.3,10,11 The persistence of esotropia following muscle union surgery is attributed to medial rectus contracture and can be demonstrated by a positive forced duction test. The published trend is to perform medial rectus recession at the same time as muscle union surgery. Yamaguchi et al. reported 19 of 23 (83%) cases requiring combined medial rectus recession.3 Similarly, Fresina et al. combined the procedures in 33 of 33 (100%) eyes7 and Akar et al. in 26 of 35 (74%) eyes.8 In the latter series, 2 patients underwent medial rectus recession as a second-stage procedure. In all other cases, medial rectus surgery was performed at the first stage. The decision to do so was based on the forced duction test following muscle union.
In our case series, 21 eyes (72%) did not require medial rectus recession and had a successful outcome with muscle union surgery alone. The mean preoperative esodeviation in this group was 21.2 PD and improved to 5.5 PD after surgery. Eight eyes (7 patients) required a second-stage procedure to treat residual esodeviation/ocular motility restriction and had successful outcomes. Three of these patients had a preoperative limitation in abduction of -4 or more, suggesting that in these cases a combined approach may be considered at the first stage. There were no cases of overcorrection or induced postoperative diplopia.
The advantage of a combined approach is obviation of the need for a second anesthetic procedure; however, this results in a higher theoretical risk of overcorrection. A staged approach furthermore reduces the overall amount of surgery required.
Our measured mean esodeviation was smaller than that reported in other studies, which may in part explain the difference in our findings. However, we found a large spread of measured deviations in the group treated by muscle union alone (minimum: 0 PD; maximum: 60 PD). We have found that simple loop myopexy results in successful surgical and functional outcomes in patients with small and large deviations in the primary position and ocular motility restriction. Ours is the only large series to report the success of muscle union surgery alone in correcting the strabismus in heavy eye syndrome. In support of other large series, we have found retro-equitorial muscle union surgery to be an effective treatment for heavy eye syndrome. In contrast to other series, we have found the requirement for a medial rectus recession to be up to 70% lower.
- Aoki Y, Nishida Y, Hayashi O, et al. Magnetic resonance imaging measurements of extraocular muscle path shift and posterior eyeball prolapse from the muscle cone in acquired esotropia with high myopia. Am J Ophthalmol. 2003;136:482–489. doi:10.1016/S0002-9394(03)00276-9 [CrossRef]
- Krizok TH, Kaufmann H, Traupe H. New approach in strabismus surgery in high myopia. Br J Ophthalmol. 1997;81:617–618.
- Yamaguchi M, Yokoyama T, Shiraki K. Surgical procedure for correcting globe dislocation in highly myopic strabismus. Am J Ophthalmol. 2010;149:341–346. doi:10.1016/j.ajo.2009.08.035 [CrossRef]
- Yokoyama T, Ataka S, Tabuchi H, Shiraki K, Miki T. Treatment of progressive esotropia caused by high myopia – a new surgical procedure based on its pathogenesis. In: de Faber J-T, ed. Transactions: 27th Meeting, European Strabismological Association. Florence, Italy: Swets & Zeitlinger; 2001:145–148.
- Rowe FJ, Noonan CP. Surgical treatment for progressive esotropia in the setting of high-axial myopia. J AAPOS. 2006;10:596–597. doi:10.1016/j.jaapos.2006.07.013 [CrossRef]
- Leo SW, Del Monte MA. Surgical correction of myopic strabismus fixus by modified loop transposition with scleral myopexy. J AAPOS. 2007;11:95. doi:10.1016/j.jaapos.2007.01.014 [CrossRef]
- Fresina M, Finzi A, Versura P, Campos EC. Muscle belly union associated with simultaneous medial rectus recession for treatment of myopic myopathy: results in 33 eyes. Eye (Lond). 2014;28:557–561. doi:10.1038/eye.2014.15 [CrossRef]
- Akar S, Gokyigit B, Aribal E, Demir A, Göker YS, Demirok A. Surgical procedure joining the lateral rectus and superior rectus muscles with or without medial rectus recession for the treatment of strabismus associated with high myopia. J Pediatr Ophthalmol Strabisumus. 2014;51:53–58.
- Rutar T, Demer JL. “Heavy Eye” syndrome in the absence of high myopia: a connective tissue degeneration in elderly strabismic patients. J AAPOS. 2009;13:36–44. doi:10.1016/j.jaapos.2008.07.008 [CrossRef]
- Ahadzadeghan I, Akbari MR, Ameri A, Anvari F, Jafari AK, Rajabi MT. Muscle belly union for treatment of myopic strabismus fixus. Strabismus. 2009;17:57–62. doi:10.1080/09273970902953210 [CrossRef]
- Durnian JM, Maddula S, Marsh IB. Treatment of “heavy eye syndrome” using simple loop myopexy. J AAPOS. 2010;14:39–41. doi:10.1016/j.jaapos.2009.11.018 [CrossRef]