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 Table of Contents  
ORIGINAL ARTICLE
Year : 2014  |  Volume : 9  |  Issue : 3  |  Page : 291-295

Surgical Treatments in Inferior Oblique Muscle Overaction


1 Department of Ophthalmology, Eye Research Center, Rassoul Akram Hospital, Iran University of Medical Sciences, Tehran, Iran
2 Department of Ophthalmology, Mashhad University of Medical Sciences, Mashhad, Iran
3 Department of Ophthalmology, Brain and Spinal Injury Repair Research Center, Tehran University of Medical Sciences, Tehran, Iran; Department of Ophthalmology, Eye Hospital, Hannover Medical School, Hannover, Germany

Date of Submission04-May-2013
Date of Acceptance12-Aug-2013
Date of Web Publication27-Oct-2014

Correspondence Address:
Kourosh Shahraki
Department of Ophthalmology, Eye Research Center, Rassoul Akram Hospital, Iran University of Medical Sciences, Sattarkhan-Niayesh Street, Tehran 14455

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2008-322X.143355

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  Abstract 

Purpose: To compare the outcomes of surgical procedures in the treatment of inferior oblique muscle overaction (IOOA) as a common disorder of ocular motility.
Methods: This retrospective study was performed on patients with primary and secondary IOOA who underwent three surgical treatment procedures including disinsertion, myectomy and anterior transposition, between 2001 and 2011. Type of strabismus, ocular alignment, presence of pre-and post-operative dissociated vertical deviation (DVD), pre- and post-operative degree of IOOA were obtained using specified checklist.
Results: A total of 122 eyes of 74 patients with mean age of 13 ± 11.7 (range, 1-51) years were included in this study. Disinsertion was performed on 12 eyes (9.8%), myectomy in 91 eyes (74.6%) and anterior transposition in 19 (15.6%). Preoperative V-pattern and DVD existed in 67 and 17 eyes; after surgery they remained in only 10 and 8 eyes, respectively. The success rate (IOOA <+1), in disinsertion, myectomy and anterior transposition groups were 91.7%, 97.8%, and 89.5%, respectively and these measures did not change after 6 months. Overall, 53.3% (n = 65) and 38.5% (n = 47) of eyes had preoperative esotropia and exotropia. Preoperative hypertropia and hypotropia were observed in 16.4% (n = 20) and 3.3% (n = 4) of eyes, respectively. After surgery there were no cases of additional strabismus. However, residual hypertropia was seen in 9 eyes, while preoperative hypotropia increased in one patient who underwent anterior transposition surgery. Esotropia and exotropia were not observed in any surgical treatment groups postoperatively.
Conclusion: We conclude that all these three procedures are effective for treatment of primary or secondary IOOA with minimum side-effects.

Keywords: Anterior Transposition; Disinsertion; Inferior Oblique Muscle Overaction; Myectomy


How to cite this article:
Sanjari MS, Shahraki K, Nekoozadeh S, Tabatabaee SM, Shahraki KA, Aghdam KA. Surgical Treatments in Inferior Oblique Muscle Overaction. J Ophthalmic Vis Res 2014;9:291-5

How to cite this URL:
Sanjari MS, Shahraki K, Nekoozadeh S, Tabatabaee SM, Shahraki KA, Aghdam KA. Surgical Treatments in Inferior Oblique Muscle Overaction. J Ophthalmic Vis Res [serial online] 2014 [cited 2017 Mar 23];9:291-5. Available from: http://www.jovr.org/text.asp?2014/9/3/291/143355


  Introduction Top


Excessive elevation of the eyeball in intended adduction is a consequence of inferior oblique muscle over action (IOOA), which is a common disorder of ocular motility [1] and is reported in 70% of patients with esotropia and 30% of patients with exotropia. [2] These two conditions may coexist with A-pattern and V-pattern occurring due to dysfunction of oblique muscle. [3] When the major cause of A-and V-patterns are dysfunction of oblique muscle, surgical treatment is recommended. [2],[4]

There are two types of IOOA, the primary type which is bilateral of unknown cause, usually results in infantile esotropia appearing after the first year of birth. [5] The secondary type, in contrast, is unilateral and is caused by paresis or paralysis of the superior oblique muscle. [6] Several techniques are used for surgical correction of IOOA including disinsertion, extirpation and denervation, recession, myectomy and anterior transposition of IO muscle. [7],[8],[9],[10]

The weakening procedures of IO muscle spread since White and Brown reported IO disinsertion in the 1930s. Currently, myectomy of the IO and IO recession are the most widely used procedures to treat IOOA. Anterior transposition of IO is another procedure for correcting IOOA. This procedure is efficient for treatment of IOOA with coexisting dissociated vertical deviation (DVD). [8],[11]

Although several studies investigated the superiority of these operations, but none of them are the procedure of choice for IOOA correction. While retrospective studies show similarity of anterior transposition and myectomy for treatment of IOOA, [12] prospective studies indicate that anterior transposition is more effective in reduction of IOOA. [13] In addition, a randomized controlled trial (RCT) disproved any difference between myectomy and recession of IO. [14] Due to conflicts between these studies, we compared three of these procedures performed at our center including disinsertion, myectomy and anterior transposition of the IO muscle through a retrospective study.


  Methods Top


This retrospective study was performed on consecutive patients with IOOA who underwent surgical treatment at the Ophthalmology Department of Rassoul Akaram Hospital, a Tertiary Care Center in Tehran, between 2001 and 2011. All surgeries were done by attending ophthalmologists. All patients with IOOA who underwent first surgical treatment were included in this study. The surgical procedures included disinsertion, myectomy and anterior transposition of IO muscle by standard methods. The type of surgery was determined according to surgeon's preference. Patients were excluded if had prior ocular disease or surgery, restrictive strabismus, history of trauma and neurologic, genetic or craniofacial abnormalities.

The study design was approved by Institutional Review Board of Iran University of Medical Sciences. The survey was conducted in agreement with the declaration of Helsinki.

Surgical Technique

In all techniques, the IO muscle was approached through the conjunctiva and Tenon's capsule by an inferior-temporal fornix incision. Later, the lateral rectus muscle was isolated by means of a 4-0 silk bridle suture. Using muscle hooks, the IO muscle was isolated from its fascial attachments both anteriorly and posteriorly.

In myectomy, two hemostats are used, and a space of 5 mm or more was maintained between the hemostats and hence; the segment of muscle between the hemostats was resected. Cautery, ligature, or both are used for hemostasis. Disinsertion occurs at the scleral attachment of the IO muscle. In anterior transposition, The IO muscle is placed just anterior and temporal to the insertion of inferior rectus muscle.

The follow-up period was 6 months. A complete history was taken.

Patients underwent full ocular and orthoptic examinations; ocular alignment in primary position, up-gaze and down-gaze were measured by a prism cover test before and after surgery.

DVD was measured using a prism and an alternate cover test in which the eyes, in primary position, are fixed at an adjustable target at a distance of 6 meters with full refractive corrections, when these are worn. Any concurrent horizontal deviation was neutralized using a horizontal prism. Subsequently, DVD in the other eye was measured in the same way. The preoperative and postoperative binocular alignment and motility assessment included alternate prism and cover measurements in the primary position at distance and near, and distant midline up-gaze and down-gaze. The function of the oblique muscles was studied by comparing the coordinated movement of the two eyes in cardinal fields of gaze, up and right, up and left, down and right, and down and left. Oblique muscle dysfunction was graded in approximately 45° adducted eye on a nine point scale from-4 underaction to + 4 overaction. For this, the fixating abducted eye initially remained elevated approximately 30° above mid-level and was then lowered to approximately 30° below mid-level. The underactions and overactions of the oblique muscles were graded in approximately 7° increments. [13]

The records of all patients were reviewed and data were obtained using specified checklist. This checklist included patients' age, gender, type of strabismus, presence of pre-and post-operative DVD, pre-and post-operative degree of IOOA and type of surgical treatment. Checklists were filled by research staff and reviewed by project supervisor.

The success rate considered as IOOA <+1.

Statistical Analysis

The statistical analyses were performed using SPSS software (version 16.0; SPSS, Inc. SPSS, Chicago, IL, USA). Data are reported as mean ± standard deviation (SD) for continuous variables and as percentages for categorical variables. To evaluate preoperative and postoperative results, paired t-test was performed. Differences between the results of surgical treatment groups were tested using independent sample t-test and one-way analysis of variances.


  Results Top


A total of 122 eyes of 74 patients were included in this study and preoperative, postoperative and 6 months follow-up data were recorded and analyzed. Mean age of patients was 13 ± 11.7 (range,1-51) years. Out of 122 eyes, 58 (47.5%) right eyes and 64 (52.5%) left eyes underwent surgery. Unilateral IOOA in 26 (21.3%) patients and bilateral IOOA in 48 (78.7%) subjects were observed. General characteristics of patients are shown in [Table 1]. The surgical treatment included disinsertion, which was performed on 12 (9.8%) eyes, myectomy in 91 (74.6%) and anterior transposition in 19 (15.6%) eyes. The mean age was not statistically significant among the three surgical treatment groups.
Table 1: General characteristics of patients in surgical treatment groups


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Pre- and post-operative eye conditions are shown in [Table 2]. Preoperative esotropia and exotropia were present in 53.3% (n = 65) and 38.5% (n = 47) of eyes and preoperative hypertropia and hypotropia were observed in 16.4% (n = 20) and 3.3% (n = 4) of eyes, respectively. In addition, 67 (54.9%) eyes presented with V-pattern and DVD was exhibited in 17 (13.9%) subjects, preoperatively.
Table 2: Pre-and post-operative condition of involved eyes


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After surgery there were no cases of additional strabismus and residual hypertropia (residual IOOA due to residual IO muscle fibers) was seen in 9 eyes, while preoperative hypotropia increased in one patient who underwent anterior transposition surgery. Esotropia and exotropia were not observed in any surgical treatment groups postoperatively and improved in all patients.

After the operation, V-pattern remained in only 10 patients with significantly lesser degrees and DVD persisted in 8 eyes of patients including 6 eyes in the myectomy group and 2 eyes in the anterior transposition group. While postoperative DVD improved in all patients in the disinsertion group, this difference was not statistically significant (P = 0.5) [Table 2]. There was no IO muscle paralysis after surgery, but IO muscle underaction (IOUA), defined as elevation deficit in adduction with free force duction test, appeared in 4 eyes.

The success rate in the disinsertion, myectomy and anterior transposition groups were 91.7%, 97.8%, and 89.5%, respectively and these measures did not change after 6-months' follow up [Table 3] and [Table 4].
Table 3: Comparison of mean change of IOOA between surgical treatment groups by follow-up periods


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Table 4: Comparison of mean change of IOOA between surgical treatment groups by preoperative IOOA measures


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  Discussion Top


Many studies have investigated the superiority of different surgical treatments for IOOA, however there are controversies in different studies. These procedures are tenotomy, extirpation and denervation, recession, myectomy and anterior transposition of IO muscle. [7],[8],[9],[10] In the present retrospective study, there was no difference between disinsertion, myectomy and anterior transposition success rates. In addition, V-pattern and DVD improved in all patients. This study includes both pediatric and adult patients in which age ranged from 1 to 51 years.

Ghazawy et al investigated the efficacy of myectomy versus anterior transposition in a retrospective study. They showed that both procedures are effective in treatment of IOOA but myectomy is superior to anterior transposition for underaction of superior oblique muscle. [12] In a prospective comparison of anterior transposition and myectomy which was performed by Min et al on 20 children with bilateral 3+ IOOA, the success rate in anterior transposition group (85%) was much higher than myectomy group (25%). [13] Mulvihill et al performed a retrospective study on 52 patients with IOOA secondary to superior oblique paresis to examine the safety and efficacy of IO disinsertion. They concluded that this procedure is safe and effective for treatment of this type of IOOA. [15] Studies comparing disinsertion with other procedures such as myectomy and anterior transposition have been not performed yet.

In the current study, we did not include recession because it is not considered as a surgical treatment for IOOA in our hospital and it can be our study limitation. However, there are other studies comparing this procedure with myectomy and anterior transposition. In an RCT conducted by Rajavi et al, [14] both recession and myectomy had considerable effect on IOOA and although myectomy results in better correction of IOOA, the rate of underaction of IO muscle was higher in this group. Another study by Muchnick et al compared the efficacy of anterior transposition versus recession in IOOA associated with superior oblique paresis in which both procedures improved the hyperdeviation in the field of action of superior and IO muscle, similarly. [16]

Preoperative conditions such as esotropia and exotropia were not significantly different between surgical treatment groups and were not observed after operation. In the study by Min et al, hypotropia occurred in one eye out of 20 patients, however, in the present study no new patient with this condition was not detected, post operatively. [13] Moreover, in our study, residul hypertropia was observed in one patient with disinsertion, 5 patients in the myectomy and 3 patients in the anterior transposition groups but the difference was not significant between groups.

DVD improved in all three groups. There were no differences in pre- and post-operative DVD among the groups. This result was comparable to the outcomes reported by Unâovská et al in which myectomy and anterior transposition were equally effective in treating DVD. Nevertheless, IOOA treatment was more effective by anterior transposition versus myectomy. [17] As in Nowakowska et al study in which V-pattern angle was reduced by bilateral IO surgery, [18] our study also showed that V-pattern was treated in the majority of patients. We just had 7 out of 53 eyes in myectomy group and 3 of out of 9 eyes in anterior transposition group with V-pattern, after the procedure. Although V-pattern remained in none of 5 patients in disinsertion group, this difference was not significant among the groups.

We observed few side-effects in surgical procedures. Underaction of IO muscle was detected in one eye in the disinsertion group, two eyes in the myectomy group and one eye in the anterior transposition group. The rate of IOUA in disinsertion, myectomy and anterior transposition procedures has been reported 4%, 14%, and 5%, respectively. [19] In another study, the rate of IOUA was reported to be 21%. [14] Bhatta et al IOUA observed IOUA in 35% of eyes with mild and persistent symptoms in the majority of patients. [20]

Although the degree of IOOA was different in the three groups in preoperative and first week follow-up examinations, this difference was not significant at three months and at last visit. As a result, the effects of disinsertion, myectomy and anterior transposition were equal in all patients at last visit. We conclude that all these three procedures are effective in the treatment of either primary or secondary IOOA in children and adults with minimum side effects.

 
  References Top

1.Choi DG, Chang BL. Electron microscopic study on overacting inferior oblique muscles. Korean J Ophthalmol 1992;6:69-75.  Back to cited text no. 1
    
2.Caldeira JA. Some clinical characteristics of V-pattern exotropia and surgical outcome after bilateral recession of the inferior oblique muscle: A retrospective study of 22 consecutive patients and a comparison with V-pattern esotropia. Binocul Vis Strabismus Q 2004;19:139-150.  Back to cited text no. 2
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3.Caldeira JA. V-pattern esotropia: A review; and a study of the outcome after bilateral recession of the inferior oblique muscle: A retrospective study of 78 consecutive patients. Binocul Vis Strabismus Q 2003;18:35-48.  Back to cited text no. 3
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4.Rizk A,  Taalab AA. V Patterns Strabismus: Clinical Characteristics and Guidelines for Surgical Treatment. Transactions of the 30 th ESA Meeting; 2005. p. 251-254.  Back to cited text no. 4
    
5.Modi NC, Jones DH. Strabismus: Background and surgical techniques. J Perioper Pract 2008;18:532-535.  Back to cited text no. 5
    
6.Cho YA, Kim JH, Kim S. Antielevation syndrome after unilateral anteriorization of the inferior oblique muscle. Korean J Ophthalmol 2006;20:118-123.  Back to cited text no. 6
    
7.Costenbader FD, Kertesz E. Relaxing procedures of the inferior oblique; a comparative study. Am J Ophthalmol 1964;57:276-280.  Back to cited text no. 7
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8.Elliott RL, Nankin SJ. Anterior transposition of the inferior oblique. J Pediatr Ophthalmol Strabismus 1981;18:35-38.  Back to cited text no. 8
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9.Parks MM. Inferior oblique weakening procedures. Int Ophthalmol Clin 1985;25:107-117.  Back to cited text no. 9
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10. Cho YA. Treatment of marked overaction of inferior oblique: Denervation and extirpation of inferior oblique. J Korean Ophthalmol Soc 1987;28:381-386.  Back to cited text no. 10
    
11.Mims JL 3 rd , Wood RC. Bilateral anterior transposition of the inferior obliques. Arch Ophthalmol 1989;107:41-44.  Back to cited text no. 11
    
12.Ghazawy S, Reddy AR, Kipioti A, McShane P, Arora S, Bradbury JA. Myectomy versus anterior transposition for inferior oblique overaction. J AAPOS 2007;11:601-605.  Back to cited text no. 12
    
13.Min BM, Park JH, Kim SY, Lee SB. Comparison of inferior oblique muscle weakening by anterior transposition or myectomy: A prospective study of 20 cases. Br J Ophthalmol 1999;83:206-208.  Back to cited text no. 13
    
14.Rajavi Z, Molazadeh A, Ramezani A, Yaseri M. A randomized clinical trial comparing myectomy and recession in the management of inferior oblique muscle overaction. J Pediatr Ophthalmol Strabismus 2011;48:375-380.  Back to cited text no. 14
    
15.Mulvihill A, Murphy M, Lee JP. Disinsertion of the inferior oblique muscle for treatment of superior oblique paresis. J Pediatr Ophthalmol Strabismus 2000;37:279-282.  Back to cited text no. 15
    
16.Muchnick RS, McCullough DH, Strominger MB. Comparison of anterior transposition and recession of the inferior oblique muscle in unilateral superior oblique paresis. J AAPOS 1998;2:340-343.  Back to cited text no. 16
    
17.Unâovská E,  Vanaurova J. Anterior transposition versus myectomy of the inferior oblique muscle in the treatment of dissociated vertical deviation. Scr Med (Brno) 2003;76:111-118.  Back to cited text no. 17
    
18.Nowakowska O, Broniarczyk-Loba A, Loba PJ. The reduction of A-V patterns with oblique muscles overaction in unilateral and bilateral surgery. Klin Oczna 2008;110:361-363.  Back to cited text no. 18
    
19.Ela-Dalman N, Velez FG, Felius J, Stager DR Sr, Rosenbaum AL. Inferior oblique muscle fixation to the orbital wall: A profound weakening procedure. J AAPOS 2007;11:17-22.  Back to cited text no. 19
    
20.Bhatta S, Auger G, Ung T, Burke J. Underacting inferior oblique muscle following myectomy or recession for unilateral inferior oblique overaction. J Pediatr Ophthalmol Strabismus 2012;49:43-48.  Back to cited text no. 20
    



 
 
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  [Table 1], [Table 2], [Table 3], [Table 4]



 

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