|Year : 2015 | Volume
| Issue : 3 | Page : 123-125
Comparison of outcome of inferior oblique weakening procedures, myectomy and anterior transposition, from western India
Nikhil Rishikeshi1, Parikshit Gogate2, Arokiam John Bosco3
1 Department of Pediatric Ophthalmology, H.V Desai Eye Hospital, Pune, Maharashtra, India
2 Department of Pediatric Ophthalmology, H.V Desai Eye Hospital; Dr. Gogate's Eye Clinic, Pune, Maharashtra, India
3 Department of Pediatric Ophthalmology, H.V Desai Eye Hospital, Pune, Maharashtra; Specialist in Ophthalmology, Indira Gandhi Government General Hospital and Post Graduate Institute, Puducherry, India
|Date of Submission||18-Apr-2014|
|Date of Acceptance||01-Nov-2014|
|Date of Web Publication||20-Aug-2015|
Gogate's Eye Clinic, K-102, Kumar Garima, Tadiwala Road, Pune-411 001, Maharashtra
Source of Support: None, Conflict of Interest: None
Context: Inferior oblique (IO) weakening is one of the commonest surgical procedures on the oblique muscles. Purpose: To compare the results of two IO weakening procedures, myectomy, and anterior transposition, done for IO over-action and dissociated vertical deviation (DVD). Setting and design: Tertiary eye-care center. Retrospective review Materials and Methods: Patients operated for IO over-action and DVD were studied. All patients had undergone a comprehensive ocular examination with full orthoptic evaluation and cycloplegic refraction. In the anterior transposition of IO, the IO muscle was recessed from its insertion and placed lateral to the insertion of the inferior rectus. In myectomy, the IO tendon was cut at two sites 5 mm apart and the cut ends cauterized and left free. The outcome measure was pre and post-operative IO action measurement. Statistical analysis: T-test. Results: Eighty six children (128 eyes) underwent IO weakening procedures, 81 (62.4%) were myectomy and 47 (36.2%) were anterior transpositions. The average age was 8.9 years (standard deviation, SD 3.51), 53 (61.6%) were girls. Twenty-three had DVD and 42 patients had bilateral IO surgeries. Thirty-eight (44.2%) had esotropia and 47 (54.6%) had exotropia co-existent; one had only primary IO over-action. The pre-and post-operative IO over-action was 1.61 and 0.59 for myectomy and 1.61 and 0.29 for anterior transposition, respectively. On comparing the pre- vs post-IO action, P < 0.001 for both techniques, but post-operative anterior transposition versus myectomy had P = 0.156 by the t-test. Conclusion: Both techniques were effective and the difference between the two techniques was not statistically significant.
Keywords: Inferior oblique, myomectomy, strabismus surgery
|How to cite this article:|
Rishikeshi N, Gogate P, Bosco AJ. Comparison of outcome of inferior oblique weakening procedures, myectomy and anterior transposition, from western India. J Clin Ophthalmol Res 2015;3:123-5
|How to cite this URL:|
Rishikeshi N, Gogate P, Bosco AJ. Comparison of outcome of inferior oblique weakening procedures, myectomy and anterior transposition, from western India. J Clin Ophthalmol Res [serial online] 2015 [cited 2022 Jan 26];3:123-5. Available from: https://www.jcor.in/text.asp?2015/3/3/123/163244
Inferior oblique (IO) over-action is the commonest cyclovertical muscle dysfunction encountered in clinical practice. Numerous procedures like myectomy and anterior transposition have been tried with different results. While there have been several studies from developed countries like US, Australia, and UK, ,,, there have been few studies from developing countries like India which has a significant population of children with strabismus. , The IO can be weakened by varied procedures as disinsertion, myotomy, myectomy, graded anterior transposition, denervation/extirpation, IO recession, resection with anterior transposition, and nasal myectomy. 
Review of literature reveals that anterior transposition of IO, in which the IO muscle is recessed from its insertion and placed lateral to the insertion of the inferior rectus, effectively corrects IO over-action (IOOA) and dissociated vertical deviation dissociated vertical deviation (DVD). , But there have been few comparisons of this with myectomy, the traditional technique in which the IO tendon is just cut and the cut ends cauterized and left free.  Our aim in this study was to review case records of our series of patients who had undergone surgeries with or without displacement associated with IO-weakening procedure by myectomy or anterior transposition and to compare the results of these two procedures.
| Materials and Methods|| |
Records of patients who were diagnosed with V pattern strabismus IOOA and DVD were reviewed. Clearance was obtained from the institution's ethics committee. The following data were noted: Registration number, age, gender, presentation and duration of symptoms, visual acuity, refraction, general ophthalmic examination, and a complete orthoptic evaluation. Orthoptic details consisted of deviation measurements by Hirschberg's corneal reflex, prism cover test, alternate cover test, binocularity, and stereopsis. Measurements of deviation were noted in all nine directions of gaze. Similar post-operative measurements were noted. Orthoptic measurements before and after the surgery were done by the same optometrist who had undergone special training in orthoptics. Surgical data including the diagnosis, surgical procedure done, date of surgery, surgeon's name, and complications, if any, were noted. Vertical displacements of horizontal rectus were also noted. Post-operative data included visual acuity, complications, and measurements in all gazes and stereopsis during the follow-up visits.
Patients with diagnosis of V-pattern exotropia/esotropia associated with IOOA and DVD and patients who had undergone IO weakening procedure with horizontal rectus resection or recession were included in our study. Patients with prior history of surgery were excluded. The pre-operative measurement was before (on day of or one day prior to) surgery, while post-operative was six weeks after surgery.
The IOOA was graded on a scale of + 1 to + 4 according to the grading of Robert Dale.  The cornea nearly disappears in the + 4 over-action. In the anterior transposition of IO, the IO muscle was recessed from its insertion and placed lateral to the insertion of the inferior rectus. In myectomy, the IO tendon was cut at two sites 5 mm apart and the cut ends cauterized and left free. The surgeries were all myomectomy for the first year of the study. The anterior transposition technique was introduced the second year.
| Results|| |
Eighty-six patients fulfilled the study criteria of this retrospective study, 53 (61.6%) of them were girls. Their average age was 8.9 years, standard deviation 3.5 years. The period of data collection was from 1 st January 2007 to 12th May 2009. The median age of the patients was 9 years. All children had undergone at least a 5-weeks follow-up after surgery. Of the 128 eyes operated, 81 (62.4%) underwent myectomy while 47 (36.2%) underwent anterior transposition. Twenty-three had DVD, while 42 patients had bilateral IO surgeries. Thirty-eight (44.2%) had esotropia and 47 (54.6%) had exotropia co-existent; one had only primary IOOA. Thirty-five had "V" phenomenon on diagnosis, 9 with esotropia, and 26 with exotropia.
The patients had IOOA ranging from + 1 to + 4, an average of 1.61 before surgery. The mean IOOA value for myectomy was 1.61 before and 0.59 after surgery (P < 0.01)Δ. The mean IOOA value for anterior transposition was 1.61 before and 0.29 after surgery (P < 0.001) [Figure 1]. The pre-operative over-action was similar in both the techniques and it was not found to be statistically significant (P = 0.994). The post-operative residual over-action by both the techniques was not statistically significant (P = 0.156) .
In the myectomy group, 28 surgeries had been performed for exotropia and 27 for esotropia. One patient had wound gape and was re-sutured without any further complication. A 17-year-old girl with both eye IOOA and DVD had hypotropia in the primary position following the myectomy surgery.
In the anterior transposition group, 19 surgeries had been performed for exotropia and 11 for esotropia.
| Discussion|| |
In this retrospective study, we analyzed the charts of patients, who had undergone IO surgeries in the pediatric ophthalmology department of the hospital and found both techniques to be effective and the difference was not statistically significant. Superiority of anterior transposition over myectomy had been demonstrated by a study from Korea by Min BN et. al., who compared the residual IO action following myectomy and anterior transposition. In their study of 20 cases, 85% of anterior transposed patients had normal IO action when compared to 25% normal action of IO in myectomy.  In their series, anterior transposed patients had residual IOOA of 15%, while myectomy patients had residual over-action of about 40%. In our study, hyper deviations IOOA were similarly controlled by anterior transposition as compared to myectomy, unlike the results from Korea where anterior transposition was better.  This was like the results of Ghazawy S et. al. from UK and a randomized control of Rajavi Z et al. from Iran who found myectomy and anterior transposition to be equally effective. , Myectomy was better for superior oblique underaction in the UK series.  While Shipman and Burke found myectomy slightly more effective than recession in the UK. 
Bilateral graded recession of the inferior oblique for V pattern esotropia with IOOA was studied by Calderia JA on 78 consecutive patients in Brazil. A good outcome with collapse of V pattern was noted and the authors advised bilateral weakening of IO by graded recession for deviations less than 15 Δ as the surgery had the potential to create vertical imbalance.  In our series, all the 35 children with "V" pattern had resolution of the pattern after IO surgery.
Bremer et al. speculated that the IO conversion had a depressor effect and hence post operatively some patients may develop hypotropia.  In our series, we had one patient who developed hypotropia in primary position following bilateral IO myectomy. None of our patients had superior oblique under action pre-operatively.
Guemes A and Wright KW analyzed the changes on versions and vertical alignment in primary position on 21 children (37 eyes) following graded anterior transposition. Graded anterior transposition was effective in normalizing versions and vertical alignments in primary position.  Treating IOOA and DVD by anterior transposition of IO was supported by Seawright AA and Gole GA in their study in Australia reviewing 37 procedures on 21 patients with bilateral anterior transposition. 
Anterior transposition of the IO has been recommended for long-term improvement of DVD by researchers in US and Iran. ,,, A modified form of recession, "hang-back recession" was studied by Kumar K and colleagues, which stated that the modified technique is equally effective in the management of V pattern esotropia (8 patients) and V pattern exotropia (7 patients).  A modified form of myectomy in which the muscle is partly cut at two places in form of "Z" has also been found to be useful.  Hypotropia may occur in primary position, even without superior oblique under action preoperatively. This ideally should be explained to the patient while counseling for surgery as a rare, though known, side-effect of the procedure.
A long-term follow-up of at least a few years would be valuable in comparing the efficacy and safety of the two techniques. Another limitation was the retrospective nature of the study. A randomized control trail would have been more valuable in comparing both techniques.
| Acknowledgement|| |
We thank Dr. Sudhir Taras, Prof. Sheetal Dharmadhikari and Prof. Col. Madan Deshpande for their support.
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