Research Article, Int J Ophthalmic Pathol Vol: 6 Issue: 2

Equatorial Scleral Anchor for the Weakening of the Inferior Oblique Muscle

Sabetti L^1*, Tomarchio S², Piozzi E³ and Magli A⁴

¹Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, L’Aquila, Italy

²Studio Tomarchio, Private Practice, Catania, Italy

³Department of Paediatric Ophthalmology, Niguarda Hospital, Milan, Italy

⁴Department of Medicine and Surgery, University of Salerno, Salerno, Italy

*Corresponding Author : Lelio Sabetti, MD
Via Eurialo 7, 00181 Rome, Italy
Tel: +39 331 43 83 795
E-mail: studiosabetti@yahoo.it

Received: May 02, 2017 Accepted: May 10, 2017 Published: May 17, 2017

Citation: Sabetti L, Tomarchio S, Piozzi E, Magli A. (2017) Equatorial Scleral Anchor for the Weakening of the Inferior Oblique Muscle. Int J Ophthalmic Pathol 6:2. doi: 10.4172/2324-8599.1000202

Abstract

Keywords: Equatorial scleral anchor; Inferior oblique overaction; Strabismus surgery; Hypertropia; Gobin’s point; Inferior oblique weakening; Tendon sparing

Introduction

The aim of the study was to determine the efficacy of a new surgical approach called “equatorial scleral anchor” aimed at reducing overaction of the inferior oblique (IO) muscle. Horizontal strabismus may commonly develop with either primary (commonly occurring with horizontal strabismus) or secondary (usually due to ipsilateral superior oblique paresis) inferior oblique overaction. A previous report of the incidence of hypertropia in pediatric population (younger than 19 years of age) was carried out by Tollefson et al. where the higher rate of hypertropia was associated with the higher prevalence (71.4% of children) of fourth cranial nerve palsy and with primary inferior oblique overaction [1]. Hyperfunction of the IO may predict a potential consecutive exotropia postsurgical procedure for esotropia [2]. The surgical treatment consists of sewing the muscle to the sclera at the Gobin’s point with tendon sparing and also performing a micro-incision to limit local tissue trauma and to induce a faster recovery [3,4].

Methods

A total of 150 patients with overactive inferior oblique muscle were enrolled between March 2012 and March 2015 to receive randomly the Tomarchio-Sabetti procedure or surgical treatment of strabismus with the inferior oblique anterior transposition (IOAT). Patients were divided into two groups: Group I consisted of 82 patients aged 5-51 years (median age 25.6 years) whose entire body of the muscle was sutured onto the sclera in correspondence with the Gobin’s point (anteroposition of the inferior oblique muscle with the bulbar insertion to the equator) using a non-absorbable 5-0 GORE-TEX suture with tendon sparing; Group II (control) of 68 patients aged 6-52 years (median age 26.3 years) (IOAT) using an absorbable 6-0 Vycril suture. Subjects underwent a comprehensive ophthalmological and orthoptic examination. Follow-ups were carried out at 1, 3, 6, 12 and 24 months postoperatively. The results we hereby present are at a 24- month follow-up are Tables 1 and 2 report the detailed description of the clinical cases and the angular deviations. SE

Table 1: Preoperative Group I (Tomarchio Sabetti Technique).

Table 2: Preoperative Group II (control group, inferior oblique anterior transposition IOAT).

Results

Twenty-one patients (25.6 %) from Group I Vs 18 (26.4%) from Group II reported pain in ocular motility (due to suture fixation), in all cases solved in 14 days. One case of subjective intorsion from Group I was spontaneously solved after 30 days, with no angular modification in primary position. Six patients (7.3%) from Group I showed a milder hypofunction than 8 cases (11.76%) in Group II. In 11 subjects (13.4%) from Group I a mild hyperfunction was observed compared to 11 patients (16.17%) from Group II. No overcorrection and antielevation syndrome was diagnosed following surgery of patients in Group I. In contrast, a hypercorrection along with the presence of the antielevation syndrome was observed in 3 patients (4.41%) from Group II.

All patients recorded a significant reduction in the hyperfunction of inferior oblique muscle. The results in terms of correction in the deviation angle appear to be similar. The only relevant difference observed was the absence of the antielevation syndrome when using the new surgical technique. The deviation results are illustrated in Tables 3 and 4.

Table 3: Group I at a 24-month postoperative follow-up.

Table 4: Group II at a 24-month postoperative follow-up.

Discussion

Recession of the inferior oblique muscle (IO) was indicated by Parks as the most effective and longer lasting procedure for IO weakening [5]. However in the 1970s, anatomical studies introduced new tables for graded muscle recession (8–10 mm IOR corrects 9–15 prism dioptres central gaze hypertropia) [6]. Recently, Metten et al. published a new dose-response study having performed 0.5°/mm up to 1.4°/mm inferior oblique recession procedures [7]. We observed one case of subjective transient intorsion, the randomness of the observation is supported by the numerous studies underlining how the inferior oblique anterior transposition techniques do not determine a potential increase in incyclotorsion [3,5,8-10]. Several studies have been carried out in order to assess the efficacy of inferior oblique surgery in the management of patients with hypertropia [3,6,11,12]. The recession of the inferior oblique muscle showed favourable results in patients with superior oblique palsy exhibiting overelevation in adduction [12]. Morover, Parks reported lower recurrence rates of overaction following inferior oblique muscle recession [5]. Due to its anatomical position, IO works as an extorter and elevator muscle, in order to make our recession with anterior Gobin’s position procedure effective in reducing the IO overaction, it was necessary that all posterior body fibers were fully hooked. We must suture the muscle closer to the inferior rectus in order to increase the depression. The insertion of the IO near the lateral rectus increases the action of abduction with an effective action of depression. If the IO is wrongly transposed in a slightly more advanced position with respect to the equator and closer to the inferior rectus muscle insertion, it will start working as an intortion tonic depressor muscle with a resulting antielevation syndrome. Equally to further increase the capacity of the depression, it is possible to insert the non-absorbable suture in the muscle further away from the scleral insertion of the inferior oblique and to suture it at the sclera beyond the equator line, with the risk of an anti-elevation syndrome. The obtained IO muscle weakening is due to two different mechanisms: anchor at the Gobin’s point (as in the recession shifted forward procedure) and reduction of the total muscle length. The IO muscle measured from the lacrimal crest of the maxillary bone at its insertion point on the inferior-lateral quadrant of the sclera into the rear hemisphere is sized 37 mm and thanks to our surgical technique the entire muscle is working actively on the Gobin’s point. If we consider that the portion between the scleral point and the site of the suture insertion is approximately 11 mm long, the final muscle active portion we reached is therefore 26 mm (37mm-11mm = 26mm). On the contrary in the IOA procedure, the final muscle active portion obtained with the normal recession shifted forward treatment is the whole muscle (37 mm). In conclusion, the equatorial scleral anchor produces the same anatomical result of an 11 mm IO muscle resection but with the benefit of not having to cut the muscle and it provides also a considerably greater improvement compared with the well-known recession shifted forward procedure.

Conclusion

Whilst the technique could still be improved and refined, it offers additional benefits such as no or minimal risk of developing vorticose haemorrhage, of hooking the muscle with the lateral rectus muscle, of post-surgical adherence and no risk of anti elevation syndrome. The new technique offers the advantages of being simple, safe, reversible and modular in terms of suturing. The classic inferior oblique anterior transposition technique provides a similar outcome but with the limited risk of antielevation syndrome. The equatorial scleral anchor procedure can be also performed through micro-incision, minimizing related tissue trauma, inducing a faster recovery and reducing the risks of a postoperative adherence syndrome

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