|Year : 1998 | Volume
| Issue : 1 | Page : 21-24
Comparison between adjustable and non-adjustable hang-back muscle recession for concomitant exotropia
K Mohan, J Ram, A Sharma
Department of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
Department of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
We compared the results of strabismus surgery using adjustable and non-adjustable hang-back muscle recessions in 38 patients having concomitant exotropia. The two groups were matched for age of the patient, type of concomitant exotropia, amount of deviation, and type and amount of muscle surgery. At 6 months follow-up, 18 of the 19 patients (95%) in the adjustable hang-back recession group and 17 of the 19 patients (90%) in the non-adjustable hang-back recession group had ocular alignment within 10 prism diopters (PD) of orthophoria. At the most recent follow-up (mean 3.4 years), 12 of the 13 patients (92%) in adjustable hang-back recession group and 12 of the 14 patients (86%) in non-adjustable hang-back recession group had ocular alignment within 10 PD of orthophoria. There was no statistically significant difference in success rates between the two groups at 6 months postoperatively and at the most recent follow-up. This preliminary study suggests that non-adjustable hang-back muscle recession can be considered for routine concomitant exotropia.
Keywords: Adjustable sutures, hang-back recession, concomitant exotropia
|How to cite this article:|
Mohan K, Ram J, Sharma A. Comparison between adjustable and non-adjustable hang-back muscle recession for concomitant exotropia. Indian J Ophthalmol 1998;46:21-4
Hang-back muscle recession is an integral part of adjustable strabismus surgery, and has also been used for non-adjustable surgery for routine concomitant strabismus.[3-5] Adjustable sutures, popularised by Jampolsky in 1975, have undoubtedly proved most useful in complicated strabismus such as Duane's retraction syndrome, paralytic strabismus, strabismus associated with myopathies and reoperations. However, some authors[6-8] have reported excellent results with adjustable suture technique for both routine as well as complicated strabismus patients. Several studies have established superiority of adjustable suture surgery over conventional, fixed suture surgery.,, We routinely use the hang-back recession technique for horizontal and vertical strabismus surgeries. To our knowledge, there is no reported study on comparison between adjustable suture surgery and non-adjustable hang-back suture surgery.
This prospective study was aimed at comparative evaluation of adjustable and non-adjustable hang-back muscle recessions for concomitant exotropia in patients matched for age, type of exotropia, angle of deviation, and type and amount of muscle surgery.
| Materials and Methods|| |
This study had 38 patients aged 15 to 25 years with concomitant exotropia which included divergence excess intermittent exotropia (10 patients), basic intermittent exotropia (14 patients), and constant exotropia (14 patients). Concomitant exotropia was categorised according to Duane's classification of exodeviation.13 All the constant exotropias were alternating. All patients had ocular deviation of 32-42 prism diopters (PD), normal extraocular muscle function, and steady central fixation. Patients having amblyopia, corneal or lenticular opacities, and fundus pathology were excluded. A detailed evaluation for strabismus which included cover test, and measurement of angle of deviation and binocular functions on synoptophore, was undertaken. Refractive error, if any, was corrected. Using stratified randomization method, patients in each exotropia group were allotted to adjustable and non-adjustable hang-back muscle recession surgery. One-half of the patients in each exotropia group underwent adjustable suture hang-back recession of the lateral rectus muscle, whereas the other half of the patients were operated using non-adjustable hang-back suture technique by one surgeon (KM). Resection of the medial rectus muscle was performed using conventional technique for both adjustable and non-adjustable surgery groups. The same surgical guidelines were used for both groups of patients [Table - 1]. Surgery was performed under local anaesthesia using 2% lignocaine and bupivacaine mixture in 1:1 ratio. The technique used for adjustable suture hang-back recession was essentially the same as described by Metz, with the modification that over-recession of the muscle by 1 mm as recommended by him, was not done. The technique used for hang-back muscle recession in non-adjustable surgery was same as that for adjustable surgery. Surgery was aimed at a postoperative overcorrection of 8 PD in all patients. Adjustment was done 24 hours after surgery if there was exotropia or more than 8 PD of esotropia.
Post-operative alignment was determined on synoptophore on the first postoperative day, at 6 months, and at the time of the most recent follow up by an unbiased observer. The procedure was considered successful if the motor alignment at 6 months was within 10 PD of orthophoria.
| Results|| |
On the first postoperative day, 17 of the 19 patients (89.5%) in the adjustable hang-back recession group and all the 19 patients (100%) in the non-adjustable hang-back surgery group had ocular alignment within 8 PD of esotropia. Two of the 19 patients (10.5%) in the adustable surgery group had exotropia and required adjustment of the sutures. The surgical outcome 6 months postoperatively is presented in [Table - 2]. [Table - 3] lists similar data at the time of the most recent follow-up. The mean length of follow-up was 3.1 years for the adjustable hang-back recession group and 3.6 years for the non-adjustable hang-back recession group. There was no statistically significant difference in the overall success rates of adjustable hang-back recession and non-adjustable hang-back recession at 6 months postoperatively (p=0.55) and at the time of the most recent follow up (p=0.59). On comparing the surgical outcome at 6 months and at the most recent follow up, the postsurgical drift (undercorrection) rose from 5% to 8% in the adjustable surgery group and from 5% to 14% in the non-adjustable hang-back recession group [Table - 2] and [Table - 3].
There was no difference in the post-surgical drift in divergence excess exotropia versus basic exotropia. [Table - 4] presents success rates for various types of exotropia treated with each technique. At 6 months postoperatively, the difference in success rates between adjustable and non-adjustable hang-back recessions for various types of exotropia was not statistically significant (p>0.05).
| Discussion|| |
Adjustable sutures allow the surgeon to alter eye alignment postoperatively in order to prevent immediate, large overcorrections or undercorrections. These sutures are usually placed on a muscle being recessed. Hang-back technique of muscle recession is required for adjustable strabismus surgery., However, this technique of muscle recession is also used for performing non-adjustable strabismus surgery, and has been found to be a simple and safe alternative to conventional recession. Adjustable suture strabismus surgery undoubtedly has a better success rate than that with conventional, fixed suture surgery.,, We attempted to find out whether adjustable suture surgery was better than non-adjustable hang-back suture muscle recession for routine, concomitant exotropia. The angle of exotropia 32-42 PD was selected for this study because we considered that this amount of deviation had better chances of success with one surgery in comparison to deviations larger than this. We measured the postoperative deviation on the synoptophore. As this instrument may give erroneous results, ideally the ocular alignment should have been determined using the prism and alternate cover test.
Equal amounts of surgery for patients with similar deviation often result in dissimilar amounts of correction, thus making it impossible to predict accurately the final surgical outcome for an individual patient. The results of the present study were interesting. In the immediate postoperative period, the adjustable hang-back recession group patients compared well with the non-adjustable hang-back recession group only after adjustment in two of the 19 cases (10.5%) though the two groups were matched for age, type and amount of exotropia, and the surgical planning. Perhaps, there are still some unknown factors related to structure and physiology of an extraocular muscle that can influence the surgical outcome in a particular patient. We did not find any statistically significant difference in success rates of adjustable and non-adjustable hang-back recessions on short term as well as long term follow up. We feel that a difference of 6% in success rates between the two groups at the most recent follow up is too low to be considered even clinically significant. In hang-back muscle recession surgery, we inadvertently perform recession more than the measured amount because of central muscle sag. In fact overcorrections rather than undercorrections have occurred more frequently with the hang-back recession technique than with conventional recession., This indicates that a greater surgical effect is achieved with hang-back surgery, and new guidelines, with reduced amount of surgery have been suggested to decrease the frequency of overcorrections., However, there was a post-surgical undercorrection, especially in the non-adjustable group in this study. The undercorrection rose from 5% to 14% in the non-adjustable group and from 5% to 8% in the adjustable group. This could be due to anterior migration of the muscle fibres due to contraction of the pseudotenon. The type of concomitant exotropia also did not have a significant bearing on success rates of the two techniques.
In view of the lack of a statistically significant difference in success rates between the two techniques, this preliminary study suggests that non-adjustable hang-back muscle recession rather than adjustable surgery may be considered for routine, concomitant exotropia. Adjustable suture surgery requires extra-planning and effort, and could be performed when doubt exists about the surgical outcome. However, preoperative assessment may not identify patients who might benefit from adjustment in the postoperative period. Failure to find a statistically significant difference could perhaps be due to small number of patients in this study. A larger series of patients needs to be studied to reveal the difference if it exists.
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[Table - 1], [Table - 2], [Table - 3], [Table - 4]