- Email: [email protected]
Comparison of plication and resection in large-angle exotropia
Comparison of plication and resection in large-angle exotropia Jaspreet Sukhija, MD, and Savleen Kaur, MD BACKGROUND
Plication of the rectus muscles is used sparingly as a tightening procedure compared to resection, however, the relative efficacy of these procedures is difficult to assess because the sparse literature comparing the two is further limited by a lack of imaging. This case series attempts to compare the techniques in cases of exotropia along with quantitative assessment of ultrasound biomicroscopy (UBM).
METHODS
Patients with exotropia of 30D-50D who had undergone first-time horizontal strabismus surgery were recruited and prospectively underwent UBM evaluation 1 year after surgery. Plication was performed by folding the anterior part of the medial rectus muscle posteriorly and tying it at the insertion to the sclera. Resection was performed in a routine manner. Deviation and motility were assessed postoperatively, when UBM was performed. Only patients with basic comitant exotropia without any vertical pattern were included.
RESULTS
During the study period, 15 patients underwent resection of the medial rectus and 13 underwent plication. The two groups were age and deviation matched preoperatively. The patients undergoing plication and resection fared equally in terms of postoperative deviation (P 5 0.81) and abduction limitation (P 5 0.169). UBM could identify and quantify plication in all cases with excellent agreement with the operative data (intraclass correlation coefficient 5 0.886; P 5 0.000).
CONCLUSIONS
Medial rectus plication or resection performed for similar angles of exotropia produced quantitatively similar results. Plication offered the advantage of being characteristically identifiable and measurable on UBM. ( J AAPOS 2018;22:348-351)
R
ectus muscle plication has recently attracted attention as an alternative to resection in exotropias of varying degree. In contrast to resection, it is a vessel-sparing procedure that permits simultaneous operations on multiple rectus muscles.1-4 Other advantages of rectus muscle plication include its relative simplicity and short operating time as well as the prospect of less surgical trauma, inflammation, and hemorrhage than resection procedures. The procedure is also potentially reversible in the early postoperative period. However, it has been shown that the effect of plication and resection of the medial rectus muscle is less linear and predictable compared to surgery on the lateral rectus muscle.5 The position of the plicated muscle postoperatively has never been evaluated on imaging, although ultrasound biomicroscopy
Author affiliation: Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India Submitted October 25, 2017. Revision accepted May 18, 2018. Published online September 18, 2018. Correspondence: Dr. Jaspreet Sukhija, MD, Advanced Eye Centre, PGIMER, Sec 12, Chandigarh, India (email: [email protected]). Copyright Ó 2018, American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved. 1091-8531/$36.00 https://doi.org/10.1016/j.jaapos.2018.05.017
348
(UBM) has been widely used as a noninvasive tool in identifying extraocular muscles.6-12 The purpose of the present study was to compare resection of the medial rectus muscle with plication in the treatment of exotropia and to provide quantitative assessment on UBM.
Subjects and Methods This study was approved by the Ethics Committee of the Post Graduate Institute of Medical Education and Research, Chandigarh, and conformed to the tenets of the Declaration of Helsinki. Consecutive patients with exotropia of 30D-50D who had undergone horizontal strabismus surgery were recruited from the strabismus clinic of the Eye Centre, PGIMER, Chandigarh, after detailed informed consent was taken. All patients operated on by the same surgeon (JS), experienced in both techniques, between November 1, 2014, and October 31, 2015, were considered for inclusion. Although plication has been a surgical option for many years, the literature on plication is sparse, and a definitive statement on its advantages compared to resection is wanting. We have previously published a large series on UBM6 and with a new UBM machine we wanted to highlight our initial experience and add to the existing knowledge on plication. Patients were divided into two groups according to whether the medial rectus was resected or plicated (combined with antagonist lateral rectus recession) during the study period. We included
Journal of AAPOS
Volume 22 Number 5 / October 2018 patients at least 18 years of age (for patient cooperation for UBM) and those with a minimum follow-up of 1 year. We excluded patients with history of previous strabismus surgery or retinal detachment surgery (scleral buckles) or glaucoma drainage devices, with eyes having structural abnormalities (eg, microphthalmia or microcornea), and those with incomitance and refractive errors. Data collected included patient age; laterality; best-corrected visual acuity; dilated cycloplegic refraction, anterior segment and posterior segment examination; extraocular movements and deviation as measured by the prism bar cover test for distance and near. Ocular motility was assessed on a four-point scale with a minimum limitation of duction marked as 1 and a maximum as 4. Postoperatively all patients were recalled 1 year postoperatively for a repeat strabismus evaluation. At the same visit, a 50 MHz UBM evaluation of muscle insertion from limbus and morphology of the muscle was performed by an examiner masked to surgical technique. Postoperative clinical evaluation was performed by an examiner masked to the surgical procedure.
Surgical Methods All patients were operated using the Parks dosage tables7 assuming that plication brought a similar effect to that of resection by a single surgeon (JS). After informed consent under operating microscope and local anesthesia; the recession of the lateral rectus was done first in all cases. The resection procedure was a standard one that involved shortening the muscle by cutting the calculated amount and hence tightening the muscle. Plication was performed as described by Chaudhuri et al5 and involved passage of absorbable sutures on both sides of the muscle margins at a distance calculated in the same way as resection; passage of scleral sutures on both sides of the insertion and folding of the muscle over a temporarily placed iris sweep so that the anterior tendon folded posteriorly against the globe (muscle-sclera plication). Conjunctiva was closed with interrupted sutures in all cases by an 8-0 polyglactin 910 suture. Postoperatively all patients received an antibiotic steroid topical combination in tapering doses for 3 weeks.
UBM Measurements In this study we used the Quantel UBM Aviso (Aviso Medical SA, Clermont Ferrand, France). The UBM was performed using a 50 MHz probe. Scanning was performed by single examiner, with the patient in the reclined position using topical anesthesia in the outpatient clinic. We used the clearscan tips; hence there was no need of applying a cup. The UBM transducer was held tangentially over the muscle to be scanned and moved to and fro over the limbus, with the oscillations perpendicular to the limbus until a cross section of the muscle insertion was observed. The patient was instructed to fix the gaze in abduction for the medial rectus muscle and in adduction for the lateral rectus muscle. The real-time image displayed on a video monitor was recorded on videotape for later analysis. The true muscle belly was visualized by the UBM as a hypo reflective area that created a distinct dark linear shadow. The muscle insertion was delineated and its distance was measured from the limbus using inbuilt
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Table 1. Baseline parameters of the two study groups Characteristic Age, years Sex: males/females Preoperative deviation, PD LogMAR visual acuity (operated eye)
Resection (n 5 15)
Plication (n 5 13)
P value
24.86 9.58 8/7 43.2 5.2
21.66 2.49 8/5 46.5 4.27
0.234 0.718 0.078
0.04 0.07
0.13 0.19
0.074
PD, prism diopter. calliper in the UBM machine. Average of three readings was taken for both the medial and lateral rectus muscle. During recording the observer was masked to all clinical data. Outcome measures were as follows: deviation, with surgical success defined as final deviation within 8D of the preoperative deviation; full extraocular motility; appearance on UBM; and confirmation of insertion of muscle on UBM.
Statistical Analysis Statistical analysis was performed using the SPSS software (IBM SPSS Statistics for Windows, Version 21.0; IBM Corp, Armonk, NY). Descriptive analysis and a comparison of means between the groups was performed using the t test. Pre- and postoperative data in either group was compared using the paired t test. Intraclass correlation coefficient (ICC) was used to assess the reliability of the UBM technique by comparing its measurements with those taken during surgery. Values between 0.81 and 1.00 were considered excellent; between 0.61 and 0.80, good. A P value of \0.05 was considered significant. Results are expressed as mean with standard deviation.
Results During the study period 15 patients (8 males) underwent resection of the medial rectus; 13 (8 males), plication. In 14 patients, the right eye was operated; in 14, the left eye. The two groups were comparable preoperatively in terms of age (range, 18-45 years) and deviation (range, 30D-50D). See Table 1. All patients underwent unilateral horizontal strabismus surgery with nonadjustable sutures. No significant difference in preoperative ocular motility was noted between the resection and plication patients (P 5 0.165). There was a significant improvement from the preoperative deviation for both groups (P 5 0.000). None of the patients had a residual or consecutive deviation of .8D for near or distance. The postoperative data for both groups is detailed in Table 2. There were no cases of ocular surface problems like dellen or granulomas in either group. Appearance on UBM All patients underwent a UBM evaluation at 1 year after surgery. All muscle insertions could be well delineated on the UBM. For all muscles, postoperative UBM measurements for muscle insertion from limbus were within acceptable limits of 1 mm of the expected site of insertion. A
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Table 2. Comparison of postoperative data Parameter
Resection
Plication
P value
Postoperative deviation, PD Abduction deficit (absolute values) Mean resection/plication of MR, mm Medial rectus insertion on UBM, mm Mean amount of resection/plication on UBM, mma Mean follow-up, months Need for reoperation at last follow-up
3.33 4.45
3.33 4.77
0.813
0.16 0.39
0.00 0.17
0.169
6.33 0.36
6.19 0.38
0.327
5.56 0.45
5.9 0.34
0.343
6.09 0.45 14.5 1.0 Nil
14.26 1.4 Nil
0.654
MR, medial rectus muscle; PD, prism diopter; UBM, ultrasound biomicropscopy. a Resection could not be assessed on UBM.
representative UBM image to depict the appearance of a resected and plicated muscle is shown in Figure 1. Although masked to the preoperative and operative data, the examiner could easily identify whether the medial rectus muscle was plicated or resected. Moreover, the examiner could assess the amount of plicated muscle by measuring the double shadow seen in case of a plicated muscle (Figure 1D). In 1 patient the upper edge of the plicated muscle seemed to have migrated posteriorly as seen on the UBM and the lower shadow was used to calculate the amount of plication. The patient, however, did not have any residual exotropia (postoperative deviation was 2D of esotropia). The examiner measuring the postoperative deviation was masked to the procedure. There was excellent agreement in the amount of medial rectus plicated as calculated on UBM and that in the operative notes for all patients (Table 3) (ICC 5 0.886; P 5 0.000).
Discussion Rectus muscle plication was described as early as 1883.13 Wright described the procedure as modified rectus tuck.1 Unlike resection, plication avoids cutting the muscle, and it has been shown to reduce the risk of anterior segment ischemia in laboratory animals as well as humans.3,4,14 Little has been published comparing quantitative dose effects of resection and plication. Recent studies by Chaudhuri and colleagues5 and Kimura and colleagues15 have shown that plication is quantitatively equivalent to resection for horizontal rectus surgery. The results of Chaudhuri and colleagues,5 however, were not based on the same follow-up periods for plication and resection patients. Plication and resection of the lateral rectus muscle are similar, predictable, and linear, unlike surgery on the medial rectus.5 Alkharashi and colleagues,16 on the other hand, provide evidence to show that resection has a better success rate than plication; however, their study is retrospective, and the authors do not mention type of strabismus
FIG 1. A-B, Representative ultrasound biomicroscope (UBM) image showing a resected medial rectus muscle. The limbus is identified on UBM as the “corneoscleral junction” and is seen as an abrupt transition between the more sonolucent corneal stroma and the more sonoreflective sclera. The muscle is identified as a hypoechoicity that creates a dark broad linear shadow. The muscle insertion is calculated as the distance between the limbus and the first point of appearance of this hypoechoicity. C-D, Representative images of a plicated muscle showing two hypoehoic linear bands. Muscle insertion is calculated as the distance between the limbus and the first point of appearance of these hypoechoicity (C). The amount of plication is calculated as twice the length of these double shadows as seen on the UBM (D, arrow). Table 3. Amount of plication actually performed and its measurement on ultrasound biomicroscopy (UBM)
Case 1 2 3 4 5 6 7 8 9 10 11 12 13
Preoperative deviation, PD
Amount plication of MR, mm
Amount plication measured on UBM, mm
50.00 40.00 45.00 45.00 45.00 50.00 45.00 50.00 45.00 45.00 50.00 45.00 50.00
7.00 6.00 6.50 6.00 6.00 7.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00
6.80 5.11 6.20 5.80 5.60 7.20 5.80 6.20 5.90 5.90 5.80 5.80 6.10
MR, medial rectus muscle; PD, prism diopter.
and visual acuity. The mean angle of deviation in their patient cohort was 30D-32D, and their cases included virgin muscles as well as those undergoing repeat strabismus surgery with procedures such as recession-resection or plication and bilateral plication or resection.16 Our study had stringent inclusion criteria in terms of the angle of strabismus, visual acuity, and the type of strabismus. Our surgical procedure was strictly either a recession-resection or a recession-plication in one eye only. Unlike muscle-to-muscle plication, plication of muscle to sclera does not cause much cosmetic blemish.17 Because it is a tightening procedure, plication of the right medial
Journal of AAPOS
Volume 22 Number 5 / October 2018 rectus muscle causes slight limitation of abduction, thus inducing an esoshift in right gaze (while having little effect in left gaze).18 We did not find any significant abduction limitation introduced by plication, unlike the significantly high rate of incomitance noted by Alkharashi and colleagues.16 The ability of UBM to accurately identify muscle insertions is well established. With the advent of widefield UBM, the sensitivity for accurately detecting muscle insertions postoperatively has increased.6,10,11 The results of our study also demonstrate its effectiveness as an imaging modality in plication; to our knowledge, this has not been reported previously. Our results show that the plicated muscle has a typical morphology, which is easily detectable on the UBM. In all cases in our study, UBM revealed plication and computed the amount of plication accurately. Resection surgery, on the contrary, cannot be quantified postoperatively on UBM. Identifying the amount of plication could be useful in postoperative management of patients and in planning repeat strabismus surgery, if necessary. In one case in our study the upper edge was not seen parallel to the lower edge of the plicated muscle, probably the result of slippage of suture or a receding effect of muscle plication. There is no way to confirm the finding postoperatively, and no intervention was undertaken because the patient was clinically orthotropic, which itself may tell us that small changes in plication do not significantly affect the angle of deviation. Perhaps a longer follow-up or repeat strabismus surgery will inform us about the behavior of the muscle on UBM and whether the slippage has any clinical effect. It will also help us to know whether plications recede over time. Our results are limited by the small number of patients and the lack of long-term follow-up. We have studied the effect of plications in large deviations considering that the outcome in exotropia is significantly affected by the preoperative angle of deviation with smaller deviations having a better success rate.19 The results of plication along with its feasibility and ease of detection and computation by the UBM are promising. The procedure is less invasive than resection, potentially reversible, and avoids complications of muscle disinsertion (slipped/lost muscle) and at the same time is not inferior to resection in cases of large-angle exotropia. Plication is visible and measurable on UBM and thus could allow more accurate planning in patients requiring additional strabismus surgeries.
Literature Search PubMed and the Cochrane Database of Systematic Reviews were searched without date or language restriction
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on October 20, 2017, using the following terms: plication, resection, ultrasound biomicroscopy, and exotropia. References 1. Wright KW. Rectus strengthening procedures. In: Wright KW, ed. Color Atlas of Ophthalmic Surgery: Strabismus. Philadelphia, PA: Lippincott; 1991. 2. Mojon DS. A modified technique for rectus muscle plication in minimally invasive strabismus surgery. Ophthalmologica 2010;224: 236-42. 3. Wright KW, Lanier AB. Effect of a modified rectus tuck on anterior segment circulation in monkeys. J Pediatr Ophthalmol Strabismus 1991;28:77-81. 4. Park C, Min BM, Wright KW. Effect of a modified rectus tuck on anterior ciliary artery perfusion. Korean J Ophthalmol 1991;5: 15-25. 5. Chaudhuri Z, Demer JL. Surgical outcomes following rectus muscle plication: a potentially reversible, vessel-sparing alternative to resection. JAMA Ophthalmol 2014;132:579-85. 6. Thakur N, Singh R, Kaur S, Kumar A, Phuljhele S, Sukhija J. Ultrasound biomicroscopy in strabismus surgery: efficacy in postoperative assessment of horizontal muscle insertions. Strabismus 2015;23: 73-9. 7. Watts P, Smith D, Mackeen, Kraft S, Buncic JR, Abdolell M. Evaluation of the ultrasound biomicroscope in strabismus surgery. J AAPOS 2002;6:187-90. 8. Dai S, Kraft SP, Smith DR, Buncic JR. Ultrasound biomicroscopy in strabismus reoperations. J AAPOS 2006;10:202-5. 9. Solarte CE, Smith DR, Buncic JR, Tehrani NN, Kraft SP. Evaluation of vertical rectus muscles using ultrasound biomicroscopy. J AAPOS 2008;12:128-31. 10. Tamburrelli C, Salgarello T, Vaiano AS, Scullica L, Palombi M, Bagolini B. Ultrasound of the horizontal rectus muscle insertion sites: implications in preoperative assessment of strabismus. Invest Ophthalmol Vis Sci 2003;44:618-22. 11. Khan HA, Smith DR, Kraft SP. Localizing rectus muscle insertions using high frequency wide—field ultrasound biomicroscopy. Br J Ophthalmol 2012;96:683-7. 12. Kaur S, Sukhija J. The accuracy of anterior segment optical coherence tomography (AS-OCT) in localizing extraocular rectus muscles insertions. J AAPOS 2015;19:488-9. 13. Roth A, Speeg-Schatz C. Muscle plication. In: Roth A, SpeegSchatz C, eds. Eye Muscle Surgery: Basic Data, Operative Techniques, Surgical Strategy. Lisse, the Netherlands: Swets & Zeitlinger; 2001:171-2. 14. Oltra EZ, Pineles SL, Demer JL, Quan AV, Velez FG. The effect of rectus muscle recession, resection and plication on anterior segment circulation in humans. Br J Ophthalmol 2015;99:556-60. 15. Kimura Y, Kimura T. Comparative study of plication-recession versus resection-recession in unilateral surgery for intermittent exotropia. Jpn J Ophthalmol 2017;61:286-91. 16. Alkharashi M, Hunter DG. Reduced surgical success rate of rectus muscle plication compared to resection. J AAPOS 2017; 21:201-4. 17. Chaudhuri Z, Demer JL. Rectus muscle plication procedure—reply. JAMA Ophthalmol 2015;133:227. 18. Wright KW. Rectus muscle plication procedure. JAMA Ophthalmol 2015;133:226-7. 19. Gezer A, Sezen F, Nasri N, Gozum N. Factors influencing the outcome of strabismus surgery in patients with exotropia. J AAPOS 2004;8:54-60.
Plication of the rectus muscles is used sparingly as a tightening procedure compared to resection, however, the relative efficacy of these procedures is difficult to assess because the sparse literature comparing the two is further limited by a lack of imaging. This case series attempts to compare the techniques in cases of exotropia along with quantitative assessment of ultrasound biomicroscopy (UBM).
METHODS
Patients with exotropia of 30D-50D who had undergone first-time horizontal strabismus surgery were recruited and prospectively underwent UBM evaluation 1 year after surgery. Plication was performed by folding the anterior part of the medial rectus muscle posteriorly and tying it at the insertion to the sclera. Resection was performed in a routine manner. Deviation and motility were assessed postoperatively, when UBM was performed. Only patients with basic comitant exotropia without any vertical pattern were included.
RESULTS
During the study period, 15 patients underwent resection of the medial rectus and 13 underwent plication. The two groups were age and deviation matched preoperatively. The patients undergoing plication and resection fared equally in terms of postoperative deviation (P 5 0.81) and abduction limitation (P 5 0.169). UBM could identify and quantify plication in all cases with excellent agreement with the operative data (intraclass correlation coefficient 5 0.886; P 5 0.000).
CONCLUSIONS
Medial rectus plication or resection performed for similar angles of exotropia produced quantitatively similar results. Plication offered the advantage of being characteristically identifiable and measurable on UBM. ( J AAPOS 2018;22:348-351)
R
ectus muscle plication has recently attracted attention as an alternative to resection in exotropias of varying degree. In contrast to resection, it is a vessel-sparing procedure that permits simultaneous operations on multiple rectus muscles.1-4 Other advantages of rectus muscle plication include its relative simplicity and short operating time as well as the prospect of less surgical trauma, inflammation, and hemorrhage than resection procedures. The procedure is also potentially reversible in the early postoperative period. However, it has been shown that the effect of plication and resection of the medial rectus muscle is less linear and predictable compared to surgery on the lateral rectus muscle.5 The position of the plicated muscle postoperatively has never been evaluated on imaging, although ultrasound biomicroscopy
Author affiliation: Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India Submitted October 25, 2017. Revision accepted May 18, 2018. Published online September 18, 2018. Correspondence: Dr. Jaspreet Sukhija, MD, Advanced Eye Centre, PGIMER, Sec 12, Chandigarh, India (email: [email protected]). Copyright Ó 2018, American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved. 1091-8531/$36.00 https://doi.org/10.1016/j.jaapos.2018.05.017
348
(UBM) has been widely used as a noninvasive tool in identifying extraocular muscles.6-12 The purpose of the present study was to compare resection of the medial rectus muscle with plication in the treatment of exotropia and to provide quantitative assessment on UBM.
Subjects and Methods This study was approved by the Ethics Committee of the Post Graduate Institute of Medical Education and Research, Chandigarh, and conformed to the tenets of the Declaration of Helsinki. Consecutive patients with exotropia of 30D-50D who had undergone horizontal strabismus surgery were recruited from the strabismus clinic of the Eye Centre, PGIMER, Chandigarh, after detailed informed consent was taken. All patients operated on by the same surgeon (JS), experienced in both techniques, between November 1, 2014, and October 31, 2015, were considered for inclusion. Although plication has been a surgical option for many years, the literature on plication is sparse, and a definitive statement on its advantages compared to resection is wanting. We have previously published a large series on UBM6 and with a new UBM machine we wanted to highlight our initial experience and add to the existing knowledge on plication. Patients were divided into two groups according to whether the medial rectus was resected or plicated (combined with antagonist lateral rectus recession) during the study period. We included
Journal of AAPOS
Volume 22 Number 5 / October 2018 patients at least 18 years of age (for patient cooperation for UBM) and those with a minimum follow-up of 1 year. We excluded patients with history of previous strabismus surgery or retinal detachment surgery (scleral buckles) or glaucoma drainage devices, with eyes having structural abnormalities (eg, microphthalmia or microcornea), and those with incomitance and refractive errors. Data collected included patient age; laterality; best-corrected visual acuity; dilated cycloplegic refraction, anterior segment and posterior segment examination; extraocular movements and deviation as measured by the prism bar cover test for distance and near. Ocular motility was assessed on a four-point scale with a minimum limitation of duction marked as 1 and a maximum as 4. Postoperatively all patients were recalled 1 year postoperatively for a repeat strabismus evaluation. At the same visit, a 50 MHz UBM evaluation of muscle insertion from limbus and morphology of the muscle was performed by an examiner masked to surgical technique. Postoperative clinical evaluation was performed by an examiner masked to the surgical procedure.
Surgical Methods All patients were operated using the Parks dosage tables7 assuming that plication brought a similar effect to that of resection by a single surgeon (JS). After informed consent under operating microscope and local anesthesia; the recession of the lateral rectus was done first in all cases. The resection procedure was a standard one that involved shortening the muscle by cutting the calculated amount and hence tightening the muscle. Plication was performed as described by Chaudhuri et al5 and involved passage of absorbable sutures on both sides of the muscle margins at a distance calculated in the same way as resection; passage of scleral sutures on both sides of the insertion and folding of the muscle over a temporarily placed iris sweep so that the anterior tendon folded posteriorly against the globe (muscle-sclera plication). Conjunctiva was closed with interrupted sutures in all cases by an 8-0 polyglactin 910 suture. Postoperatively all patients received an antibiotic steroid topical combination in tapering doses for 3 weeks.
UBM Measurements In this study we used the Quantel UBM Aviso (Aviso Medical SA, Clermont Ferrand, France). The UBM was performed using a 50 MHz probe. Scanning was performed by single examiner, with the patient in the reclined position using topical anesthesia in the outpatient clinic. We used the clearscan tips; hence there was no need of applying a cup. The UBM transducer was held tangentially over the muscle to be scanned and moved to and fro over the limbus, with the oscillations perpendicular to the limbus until a cross section of the muscle insertion was observed. The patient was instructed to fix the gaze in abduction for the medial rectus muscle and in adduction for the lateral rectus muscle. The real-time image displayed on a video monitor was recorded on videotape for later analysis. The true muscle belly was visualized by the UBM as a hypo reflective area that created a distinct dark linear shadow. The muscle insertion was delineated and its distance was measured from the limbus using inbuilt
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Table 1. Baseline parameters of the two study groups Characteristic Age, years Sex: males/females Preoperative deviation, PD LogMAR visual acuity (operated eye)
Resection (n 5 15)
Plication (n 5 13)
P value
24.86 9.58 8/7 43.2 5.2
21.66 2.49 8/5 46.5 4.27
0.234 0.718 0.078
0.04 0.07
0.13 0.19
0.074
PD, prism diopter. calliper in the UBM machine. Average of three readings was taken for both the medial and lateral rectus muscle. During recording the observer was masked to all clinical data. Outcome measures were as follows: deviation, with surgical success defined as final deviation within 8D of the preoperative deviation; full extraocular motility; appearance on UBM; and confirmation of insertion of muscle on UBM.
Statistical Analysis Statistical analysis was performed using the SPSS software (IBM SPSS Statistics for Windows, Version 21.0; IBM Corp, Armonk, NY). Descriptive analysis and a comparison of means between the groups was performed using the t test. Pre- and postoperative data in either group was compared using the paired t test. Intraclass correlation coefficient (ICC) was used to assess the reliability of the UBM technique by comparing its measurements with those taken during surgery. Values between 0.81 and 1.00 were considered excellent; between 0.61 and 0.80, good. A P value of \0.05 was considered significant. Results are expressed as mean with standard deviation.
Results During the study period 15 patients (8 males) underwent resection of the medial rectus; 13 (8 males), plication. In 14 patients, the right eye was operated; in 14, the left eye. The two groups were comparable preoperatively in terms of age (range, 18-45 years) and deviation (range, 30D-50D). See Table 1. All patients underwent unilateral horizontal strabismus surgery with nonadjustable sutures. No significant difference in preoperative ocular motility was noted between the resection and plication patients (P 5 0.165). There was a significant improvement from the preoperative deviation for both groups (P 5 0.000). None of the patients had a residual or consecutive deviation of .8D for near or distance. The postoperative data for both groups is detailed in Table 2. There were no cases of ocular surface problems like dellen or granulomas in either group. Appearance on UBM All patients underwent a UBM evaluation at 1 year after surgery. All muscle insertions could be well delineated on the UBM. For all muscles, postoperative UBM measurements for muscle insertion from limbus were within acceptable limits of 1 mm of the expected site of insertion. A
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Table 2. Comparison of postoperative data Parameter
Resection
Plication
P value
Postoperative deviation, PD Abduction deficit (absolute values) Mean resection/plication of MR, mm Medial rectus insertion on UBM, mm Mean amount of resection/plication on UBM, mma Mean follow-up, months Need for reoperation at last follow-up
3.33 4.45
3.33 4.77
0.813
0.16 0.39
0.00 0.17
0.169
6.33 0.36
6.19 0.38
0.327
5.56 0.45
5.9 0.34
0.343
6.09 0.45 14.5 1.0 Nil
14.26 1.4 Nil
0.654
MR, medial rectus muscle; PD, prism diopter; UBM, ultrasound biomicropscopy. a Resection could not be assessed on UBM.
representative UBM image to depict the appearance of a resected and plicated muscle is shown in Figure 1. Although masked to the preoperative and operative data, the examiner could easily identify whether the medial rectus muscle was plicated or resected. Moreover, the examiner could assess the amount of plicated muscle by measuring the double shadow seen in case of a plicated muscle (Figure 1D). In 1 patient the upper edge of the plicated muscle seemed to have migrated posteriorly as seen on the UBM and the lower shadow was used to calculate the amount of plication. The patient, however, did not have any residual exotropia (postoperative deviation was 2D of esotropia). The examiner measuring the postoperative deviation was masked to the procedure. There was excellent agreement in the amount of medial rectus plicated as calculated on UBM and that in the operative notes for all patients (Table 3) (ICC 5 0.886; P 5 0.000).
Discussion Rectus muscle plication was described as early as 1883.13 Wright described the procedure as modified rectus tuck.1 Unlike resection, plication avoids cutting the muscle, and it has been shown to reduce the risk of anterior segment ischemia in laboratory animals as well as humans.3,4,14 Little has been published comparing quantitative dose effects of resection and plication. Recent studies by Chaudhuri and colleagues5 and Kimura and colleagues15 have shown that plication is quantitatively equivalent to resection for horizontal rectus surgery. The results of Chaudhuri and colleagues,5 however, were not based on the same follow-up periods for plication and resection patients. Plication and resection of the lateral rectus muscle are similar, predictable, and linear, unlike surgery on the medial rectus.5 Alkharashi and colleagues,16 on the other hand, provide evidence to show that resection has a better success rate than plication; however, their study is retrospective, and the authors do not mention type of strabismus
FIG 1. A-B, Representative ultrasound biomicroscope (UBM) image showing a resected medial rectus muscle. The limbus is identified on UBM as the “corneoscleral junction” and is seen as an abrupt transition between the more sonolucent corneal stroma and the more sonoreflective sclera. The muscle is identified as a hypoechoicity that creates a dark broad linear shadow. The muscle insertion is calculated as the distance between the limbus and the first point of appearance of this hypoechoicity. C-D, Representative images of a plicated muscle showing two hypoehoic linear bands. Muscle insertion is calculated as the distance between the limbus and the first point of appearance of these hypoechoicity (C). The amount of plication is calculated as twice the length of these double shadows as seen on the UBM (D, arrow). Table 3. Amount of plication actually performed and its measurement on ultrasound biomicroscopy (UBM)
Case 1 2 3 4 5 6 7 8 9 10 11 12 13
Preoperative deviation, PD
Amount plication of MR, mm
Amount plication measured on UBM, mm
50.00 40.00 45.00 45.00 45.00 50.00 45.00 50.00 45.00 45.00 50.00 45.00 50.00
7.00 6.00 6.50 6.00 6.00 7.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00
6.80 5.11 6.20 5.80 5.60 7.20 5.80 6.20 5.90 5.90 5.80 5.80 6.10
MR, medial rectus muscle; PD, prism diopter.
and visual acuity. The mean angle of deviation in their patient cohort was 30D-32D, and their cases included virgin muscles as well as those undergoing repeat strabismus surgery with procedures such as recession-resection or plication and bilateral plication or resection.16 Our study had stringent inclusion criteria in terms of the angle of strabismus, visual acuity, and the type of strabismus. Our surgical procedure was strictly either a recession-resection or a recession-plication in one eye only. Unlike muscle-to-muscle plication, plication of muscle to sclera does not cause much cosmetic blemish.17 Because it is a tightening procedure, plication of the right medial
Journal of AAPOS
Volume 22 Number 5 / October 2018 rectus muscle causes slight limitation of abduction, thus inducing an esoshift in right gaze (while having little effect in left gaze).18 We did not find any significant abduction limitation introduced by plication, unlike the significantly high rate of incomitance noted by Alkharashi and colleagues.16 The ability of UBM to accurately identify muscle insertions is well established. With the advent of widefield UBM, the sensitivity for accurately detecting muscle insertions postoperatively has increased.6,10,11 The results of our study also demonstrate its effectiveness as an imaging modality in plication; to our knowledge, this has not been reported previously. Our results show that the plicated muscle has a typical morphology, which is easily detectable on the UBM. In all cases in our study, UBM revealed plication and computed the amount of plication accurately. Resection surgery, on the contrary, cannot be quantified postoperatively on UBM. Identifying the amount of plication could be useful in postoperative management of patients and in planning repeat strabismus surgery, if necessary. In one case in our study the upper edge was not seen parallel to the lower edge of the plicated muscle, probably the result of slippage of suture or a receding effect of muscle plication. There is no way to confirm the finding postoperatively, and no intervention was undertaken because the patient was clinically orthotropic, which itself may tell us that small changes in plication do not significantly affect the angle of deviation. Perhaps a longer follow-up or repeat strabismus surgery will inform us about the behavior of the muscle on UBM and whether the slippage has any clinical effect. It will also help us to know whether plications recede over time. Our results are limited by the small number of patients and the lack of long-term follow-up. We have studied the effect of plications in large deviations considering that the outcome in exotropia is significantly affected by the preoperative angle of deviation with smaller deviations having a better success rate.19 The results of plication along with its feasibility and ease of detection and computation by the UBM are promising. The procedure is less invasive than resection, potentially reversible, and avoids complications of muscle disinsertion (slipped/lost muscle) and at the same time is not inferior to resection in cases of large-angle exotropia. Plication is visible and measurable on UBM and thus could allow more accurate planning in patients requiring additional strabismus surgeries.
Literature Search PubMed and the Cochrane Database of Systematic Reviews were searched without date or language restriction
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on October 20, 2017, using the following terms: plication, resection, ultrasound biomicroscopy, and exotropia. References 1. Wright KW. Rectus strengthening procedures. In: Wright KW, ed. Color Atlas of Ophthalmic Surgery: Strabismus. Philadelphia, PA: Lippincott; 1991. 2. Mojon DS. A modified technique for rectus muscle plication in minimally invasive strabismus surgery. Ophthalmologica 2010;224: 236-42. 3. Wright KW, Lanier AB. Effect of a modified rectus tuck on anterior segment circulation in monkeys. J Pediatr Ophthalmol Strabismus 1991;28:77-81. 4. Park C, Min BM, Wright KW. Effect of a modified rectus tuck on anterior ciliary artery perfusion. Korean J Ophthalmol 1991;5: 15-25. 5. Chaudhuri Z, Demer JL. Surgical outcomes following rectus muscle plication: a potentially reversible, vessel-sparing alternative to resection. JAMA Ophthalmol 2014;132:579-85. 6. Thakur N, Singh R, Kaur S, Kumar A, Phuljhele S, Sukhija J. Ultrasound biomicroscopy in strabismus surgery: efficacy in postoperative assessment of horizontal muscle insertions. Strabismus 2015;23: 73-9. 7. Watts P, Smith D, Mackeen, Kraft S, Buncic JR, Abdolell M. Evaluation of the ultrasound biomicroscope in strabismus surgery. J AAPOS 2002;6:187-90. 8. Dai S, Kraft SP, Smith DR, Buncic JR. Ultrasound biomicroscopy in strabismus reoperations. J AAPOS 2006;10:202-5. 9. Solarte CE, Smith DR, Buncic JR, Tehrani NN, Kraft SP. Evaluation of vertical rectus muscles using ultrasound biomicroscopy. J AAPOS 2008;12:128-31. 10. Tamburrelli C, Salgarello T, Vaiano AS, Scullica L, Palombi M, Bagolini B. Ultrasound of the horizontal rectus muscle insertion sites: implications in preoperative assessment of strabismus. Invest Ophthalmol Vis Sci 2003;44:618-22. 11. Khan HA, Smith DR, Kraft SP. Localizing rectus muscle insertions using high frequency wide—field ultrasound biomicroscopy. Br J Ophthalmol 2012;96:683-7. 12. Kaur S, Sukhija J. The accuracy of anterior segment optical coherence tomography (AS-OCT) in localizing extraocular rectus muscles insertions. J AAPOS 2015;19:488-9. 13. Roth A, Speeg-Schatz C. Muscle plication. In: Roth A, SpeegSchatz C, eds. Eye Muscle Surgery: Basic Data, Operative Techniques, Surgical Strategy. Lisse, the Netherlands: Swets & Zeitlinger; 2001:171-2. 14. Oltra EZ, Pineles SL, Demer JL, Quan AV, Velez FG. The effect of rectus muscle recession, resection and plication on anterior segment circulation in humans. Br J Ophthalmol 2015;99:556-60. 15. Kimura Y, Kimura T. Comparative study of plication-recession versus resection-recession in unilateral surgery for intermittent exotropia. Jpn J Ophthalmol 2017;61:286-91. 16. Alkharashi M, Hunter DG. Reduced surgical success rate of rectus muscle plication compared to resection. J AAPOS 2017; 21:201-4. 17. Chaudhuri Z, Demer JL. Rectus muscle plication procedure—reply. JAMA Ophthalmol 2015;133:227. 18. Wright KW. Rectus muscle plication procedure. JAMA Ophthalmol 2015;133:226-7. 19. Gezer A, Sezen F, Nasri N, Gozum N. Factors influencing the outcome of strabismus surgery in patients with exotropia. J AAPOS 2004;8:54-60.