Scar remodeling after strabismus surgery

Analysis of temporal changes in thickness from conjunctiva to sclera after plication of the medial rectus muscle measured by anterior segment optical coherence tomography

PURPOSE

We evaluated long-term changes in conjunctival bulge after medial rectus muscle (MR) tightening using the plication method.

STUDY DESIGN

Retrospective and observational.

METHODS

Patients who underwent MR plication for exotropia from December 2016-March 2020 at Okayama University Hospital were included. Thirty two eyes of 27 patients were enrolled. The thickness from the conjunctiva to sclera (TCS) at the limbus and insertion sites were measured using anterior segment optical coherence tomography preoperatively and 1 month, 4 months, and 12 months postoperatively. Correlations between the 1- and 12 month postoperative TCS and amount of MR tightening were analyzed.

RESULTS

Preoperative and 4 month postoperative TCS at the limbus site were not significantly different (P=0.07). The 12 month postoperative TCS at the insertion site was significantly thinner than at 1 month postoperative (P<0.01), although significantly thicker than the preoperative TCS (P<0.01). No significant correlations were found between the amount of MR tightening (in mm) and 1- or 12 month postoperative TCS at the limbus (P=0.62 and P=0.98, respectively) and insertion (P=0.50 and P=0.24, respectively) sites.

CONCLUSION

The TCS at the insertion site peaked at 1 month postoperatively, continued to decrease for longer than 4 months postoperatively, continuing until 12 months postoperatively. The TCS at the insertion site 12 months postoperatively is thicker than preoperatively. The TCS at both the limbus and insertion sites was not related to the amount of medial rectus muscle tightening.

Routine use of non-absorbable sutures in bi-medial rectus recession as a measure to reduce the incidence of consecutive exotropia

OBJECTIVE

To evaluate the incidence of consecutive exotropia following bilateral medial rectus muscle recession surgery (BMR) for esotropia using non-absorbable compared with absorbable sutures in children undergoing strabismus surgery.

METHODS

A retrospective cohort study of all children with esotropia who underwent BMR by a single surgeon in a tertiary public hospital. As of February 2018, only non-absorbable sutures were used. The primary outcome was the incidence of consecutive exotropia.

RESULTS

A total of 121 children were included in the analysis, 3.66 ± 2.62 years, 53% were male. In 80 children (66%) non-absorbable sutures were used (non-absorbable group) and in 41 children (34%) absorbable sutures were used (absorbable group). Consecutive exotropia (≥ 8 prism dioptres) occurred in ten children (24%) in the absorbable group and in three children (4%) in the non-absorbable group (OR = 8.28, 95% CI = 2.13-32.13; P = 0.002). This difference between groups remained significant after adjustment for potential confounders and follow-up time (HR = 4.98, 95% CI = 1.30-19.05, P = 0.019). Mean follow-up time was 22 and 12 months in the absorbable and non-absorbable groups, respectively (P < 0.001). Two children in the non-absorbable group had pyogenic granuloma that resolved after 3 months of topical steroidal therapy.

CONCLUSION

Routine use of non-absorbable sutures in BMR surgery for esotropia may be a preferable alternative to absorbable sutures for the prevention of consecutive exotropia.

Bilateral Medial Rectus Advancement versus Unilateral Medial Rectus Advancement with Lateral Rectus Recession for Surgical Management of Large Angle Consecutive Exotropia without Adduction Deficit

Purpose

Methods

Results

Conclusion

Augmented Lateral Rectus Recession for Consecutive Exotropia

Purpose: To evaluate the efficacy of augmented bilateral lateral rectus recession in the treatment of consecutive exotropia.Methods: We retrospectively reviewed records of nine patients who underwent augmented bilateral lateral rectus recession for consecutive exotropia with minimal adduction deficits. Our normal surgical dosing tables for bilateral lateral rectus recession were augmented by adding 1.5-2 mm. All patients had been measured preoperatively using prism and alternate cover testing (PACT), except for one patient in whom Krimsky measurements were performed because of amblyopia. Surgery was deemed successful if postoperative alignment fell within a potential monofixation range of ±10 prism diopters (PD) by PACT at the final postoperative examination.Results: Eight out of nine patients (89%) had a successful outcome. One patient was surgically undercorrected. Despite successful realignment to a state of monofixation syndrome in most patients, there was no significant restoration of stereopsis following strabismus surgery.Conclusions: Surgical augmentation of bilateral lateral rectus recession standard dosing by 1.5-2 mm is efficacious for restoring binocular alignment for both distance and near fixation. This surgical approach may be preferable to bimedial advancements in patients with minimal preoperative adduction deficits who show no significant increase in exotropia during near fixation.

Surgical management of consecutive exotropia: Long-term outcomes

PURPOSE

To compare lateral rectus recession (LRc) and medial rectus advancement (MRadv) for correction of consecutive exotropia (CXT).

METHODS

Of the 43 exotropic patients 20 of them underwent LRc (group 1) and 23 of them underwent MRadv (group 2). Postoperative exodrift, strabismic angle, dose effect relationship were compared with minimum 2 years follow‑up.

RESULTS

An average dose-effect in group 2 is higher than group 1 in the early postoperative period, however there was no significant difference at the second year follow-up (p=0,109). An average exodrift after 2 year follow-up was 6,6±7,12 PD in group 1, and 8,13±7,45 PD in group 2. Postoperative overall success rate was 50% in group 1 and 65% in group 2 at the last follow-up. The success rates were not significantly different between the groups (chi-square, p =0.31).

CONCLUSION

Although there was no statistically significant difference at the last follow-up, better results were obtained with MRadv than LRc in the treatment of CXT.

Medial Rectus Advancement for Secondary Exotropia

PURPOSE

To determine the preoperative characteristics and surgical results after medial rectus advancement in patients with secondary exotropia.

DESIGN

Retrospective, interventional case series.

METHODS

Setting: Tertiary Care University Medical Center. PatientPopulation: 221 patients with a diagnosis of secondary exotropia who underwent medial rectus advancement surgery by a single surgeon.

OBSERVATION

Preoperative demographics, exodeviation and motility, intraoperative findings, and postoperative results were recorded. MainOutcomeMeasure: Success of surgery, defined as Esotropia <15 prism diopters (pd) at postoperative week 1, or any deviation of <8 pd at postoperative month 2 (POM2).

RESULTS

A total of 98 patients underwent unilateral medial rectus advancement (UMRadv), 89 underwent UMRadv with lateral rectus recession (LRc), and 34 underwent bilateral medial rectus advancement (BMRadv). POM2 success rates were 66.7% in UMRadv patients, 62.1% in UMRadv + LRc, and 56% in BMRadv. A total of 117 patients had preoperative adduction deficits, which were significantly associated with the finding of an intraoperative stretched scar (P < .001). Larger preoperative duction deficits were associated with larger stretched scars (P < .001). At POM2, the mean effect of surgery (pd of correction/mm) was 2.3 ± 1.4 pd/mm for UMRadv, 2.5 ± 0.8 pd/mm for UMRadv + LRc, and 2.8 ± 1.1 pd/mm for BMRadv. Patients with a stretched scar had significantly less correction per millimeter (2.2 ± 1.2 pd/mm) compared with those without (2.6 ± 1.2 pd/mm, P < .001). A total of 38.6% of patients experienced exodrift greater than 10 pd. Exodrift was significantly larger in the BMRadv group (P < .005).

DISCUSSION

These results provide guidance for surgical correction based on preoperative deviation and ductions. Adduction deficits indicate a stretched scar, which must be treated with resection and advancement of the medial rectus. A larger amount of surgery is needed in patients with a stretched scar. Exodrift is common, and therefore aiming for approximately 10 pd of overcorrection at postoperative week 1 can improve final outcomes.

CONCLUSION

Medial rectus advancement results in successful surgical results at POM2 for secondary exotropia.

Management of stretched scar- induced secondary strabismus

Background

To determine characteristics and management of consecutive or recurrent strabismus secondary to stretched scar.

Methods

This is a retrospective review of all patients diagnosed with late secondary consecutive or recurrent strabismus due to stretched scar from 2012 to 2017. The diagnosis of stretched scar was made in any case of late (≥ 1 month) consecutive or recurrent strabismus associated with underaction of the previously operated muscle. The diagnosis was confirmed intraoperatively by negative forced duction test and the characteristic appearance of the scar tissue. Surgical correction involved excision of the scar tissue with muscle re-attachment to the sclera using non-absorbable sutures. Study parameters include improvement in secondary deviations, degree of muscle underaction and diplopia.

Results

21 consecutive and 6 recurrent cases of stretched scar –induced strabismus were identified and all cases were associated with variable degrees of limited ocular duction. After surgical correction of the stretched scar, consecutive deviations in the form of consecutive esotropia and exotropia were corrected by means of 26.1PD and 65.6PD while recurrent deviations in the form recurrent exotropia and recurrent hypertropia were corrected by means of 34.3PD and 11PD respectively with significant improvement of limited ocular ductions. 21 patients had diplopia at presentation and all were improved after surgery.

Conclusion

management of stretched scar –induced secondary strabismus by excision of the stretched scar and muscle fixation to the sclera using non-absorbable sutures significantly corrects secondary deviations and improves limitation of ocular duction.

Accuracy of the Ultrasound Biomicroscopy Bag/Balloon Technique in Locating Horizontal Extraocular Muscle Insertions Before and After Strabismus Surgery

PURPOSE

To investigate the accuracy of high frequency ultrasound biomicroscopy using the bag/balloon technique to locate recti muscle insertions before and after strabismus surgery.

METHODS

This was a prospective masked study. The distance from the limbus to horizontal recti muscle insertions was measured by caliper intraoperatively and ultrasound biomicroscopy preoperatively and during follow-up. Accuracy was defined as the difference between ultrasound biomicroscopy and caliper measurements.

RESULTS

Thirty-nine muscles (19 medial rectus and 20 lateral rectus) of 22 patients were included. The mean age of the patients was 34.7 ± 15.5 years (range: 18 to 78 years). Follow-up measurements were available for 25 muscles: 12 muscles were recessed and 13 were resected/advanced. Twelve of the included muscles underwent prior surgery. There was a strong correlation between preoperative mean ultrasound biomicroscopy and caliper measurements (P < .001, r_p = 0.872) without significant difference between the accuracy of identification of medial rectus and lateral rectus muscles (P = .116 and .377, respectively). On average, postoperative ultrasound biomicroscopy measurements of recessed muscles were 1.15 mm greater than caliper measurements at the end of surgery (P = .003), whereas the mean difference in the resected muscles was not statistically significant (-0.07 mm, P > .999). Overall, in 16 of 25 muscles (64%), the differences between the postoperative measurements and the end of surgery measurements were less than 1 mm. There was no correlation between the accuracy and the time of ultrasound biomicroscopy after surgery (P = .516).

CONCLUSIONS

The ultrasound biomicroscopy bag/balloon technique is an accurate and reliable method of locating recti muscle insertions before and after strabismus surgery. Ultrasound biomicroscopy may assist strabismologists in planning repeated operations. [J Pediatr Ophthalmol Strabismus. 2020;57(1):12-20.].

Postoperative Muscle Migration Through Stretched Scar Formation After Superior Rectus Muscle Nonscleral Sutured Resection in Rabbit Eyes

PURPOSE

To determine whether suturing to the residual muscle stump induces postoperative muscle migration after superior rectus muscle (SRM) resection in rabbit eyes.

METHODS

Twenty-four eyes in 12 rabbits were randomly divided into two groups. Each group underwent a 3-mm SRM resection. The muscle stump was not removed in one randomly assigned eye in each rabbit and the resected muscle was sutured to the residual muscle stump (residual muscle stump group). In the other eye, the muscle stump was completely removed and the resected muscle was sutured to the original insertion site (control group). At postoperative weeks 1, 2, and 4, the distances between the most anterior aspect of the reattached muscle and the corneal limbus were measured. Histopathologic differences at the new attachment sites were assessed between the two groups at postoperative week 4.

RESULTS

The mean distance between the corneal limbus and SRM was 2.97 ± 1.00 mm in the residual muscle stump group and 1.99 ± 0.40 mm in the control group at postoperative week 2 (P = .026) and 3.14 ± 0.78 mm in the residual muscle stump group and 1.81 ± 0.44 mm in the control group at postoperative week 4 (P = .002). Connective tissue, fibrosis, and myofibroblast proliferation in the front of the SRM were identified based on histopathologic findings.

CONCLUSIONS

Postoperative loosening associated with a stretched scar frequently occurred in cases with suturing to the residual muscle during rectus muscle resection and could result from fibrosis and connective tissue proliferation in front of the rectus muscle. [J Pediatr Ophthalmol Strabismus. 2019;56(4):254-260.].

Magnetic Resonance Imaging of the Globe-Tendon Interface for Extraocular Muscles: Is There an "Arc of Contact"?

PURPOSE

To determine if the "arc of contact" is an accurate approximation of the globe-tendon interface for the biomechanical modeling of extraocular muscle (EOM) force transfer onto the globe.

METHODS

At a single academic institution, 18 normal and 14 strabismic subjects were prospectively recruited for surface-coil enhanced magnetic resonance imaging at 312- or 390-μm resolution in axial planes for horizontal EOMs (23 subjects, 26 orbits) and sagittal planes for vertical EOMs (13 subjects, 22 orbits) during large ipsiversive ductions. The measured angle at insertion and the predicted angle assuming an "arc of contact" were compared using paired t tests.

RESULTS

For normal EOMs, the measured angle at insertion was significantly greater than predicted assuming an "arc of contact" for the medial rectus (MR) (5.0 ± 4.8 degrees vs 0.0 ± 0.0 degrees, P = .03), lateral rectus (LR) (4.9 ± 3.0 degrees vs 0.0 ± 0.0 degrees, P = .02), inferior rectus (7.4 ± 4.8 degrees vs 1.2 ± 2.6 degrees, P = .00003), and superior rectus (0.6 ± 1.1 degrees vs 0.0 ± 0.0 degrees, P = .04). In strabismic subjects, the measured angle was significantly greater for the MR in abducens palsy (9.9 ± 4.3 degrees vs 0.5 ± 0.7 degrees, P = .0007) and after MR resection (9.0 ± 6.9 degrees vs 1.2 ± 2.4 degrees, P = .02), but not after LR recession (2.9 vs 0.0 degrees). Single subjects had comparable angles after MR recession, but markedly different angles after MR and LR posterior fixation.

CONCLUSIONS

Contrary to the "arc of contact" biomechanical model, normal and postsurgical EOMs are significantly non-tangent to the globe at their scleral insertions. The "arc of contact" should be replaced in biomechanical modeling by the experimentally measured angles at tendon insertions. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Clinical and surgical risk factors for consecutive exotropia

Introduction:

Consecutive exotropia is one of the complications of esotropia surgery. Its prevalence is estimated at 4%–27%. The aim of this study was to identify the risk factors for consecutive exotropia in the aftermath of surgical treatment of esotropia.

Methods:

Seventy-four patients examined in our strabismus consultation for a consecutive exotropia from January 2010 to June 2016 were retrospectively included. The age of onset of esotropia, the presence of amblyopia, the age of esotropia surgery and chosen procedure, the refractive errors, the anomalies of ocular motility, the age of onset of the consecutive exotropia and its angle of deviation were reported. Statistical analyses were performed with Student’s test and Fisher’s exact test.

Results:

Esotropia occurred in 65% of cases before the age of 1 year, was associated with amblyopia in 51%, hyperopia in 55% or anisometropia in 31%. Surgery was performed before the age of 6 years for 55% of the patients and involved for 52% the both medial recti. The angle of deviation of consecutive exotropia was ≤20 prism dioptres (PD) in 39%, 21-40 PD in 39% and ≥ 40 PD in 22%, related to amblyopia (p = 0.028), and to high hypermetropia (p = 0.05).

Discussion:

Amblyopia and hyperopia were the most important risk factors of consecutive exotropia in our series. Early onset esotropia, stereopsis abnormalities, anisometropia, oblique dysfunction, convergence insufficiency appeared but did not reach statistical significance.

Conclusion:

Amblyopia is a major risk factor that should be taken into consideration during surgery of an esotropia.

Effects of the Rho-Kinase Inhibitor Y-27632 on Extraocular Muscle Surgery in Rabbits

Purpose

To evaluate the effect of the Rho-kinase inhibitor Y-27632 on postoperative inflammation and adhesion following extraocular muscle surgery in rabbits.

Methods

The superior rectus muscle reinsertion was performed on both eyes of 8 New Zealand white rabbits. After reinsertion, the rabbits received subconjunctival injections of the Rho-kinase inhibitor and saline on each eye. To assess acute and late inflammatory changes, Ki-67, CD11β+, and F4/80 were evaluated and the sites of muscle reattachment were evaluated for a postoperative adhesion score and histopathologically for collagen formation.

Results

F4/80 antibody expression was significantly different in the Rho-kinase inhibitor-injected group at both postoperative day 3 and week 4 (p = 0.038, 0.031). However, Ki-67 and CD11β+ were not different the between two groups. The difference in the SRM/conjunctiva adhesion score between the two groups was also significant (p = 0.034). Conclusion. Intraoperative subconjunctival injection of the Rho-kinase inhibitor may be effective for adjunctive management of inflammation and fibrosis in rabbit eyes following extraocular muscle surgery.

Intraoperative Findings in Consecutive Exotropia with and without Adduction Deficit

PURPOSE

Consecutive exotropia may be associated with limited adduction, which has been reported to be caused by 1 or more anatomic abnormalities of rectus muscles or their insertions. We studied the relative frequency of grades of adduction deficit and the relative frequency of abnormal anatomic findings.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients undergoing surgery for consecutive exotropia.

METHODS

Preoperative duction deficits were graded on a -5 (severe limitation) to 0 (normal) scale. Operative reports were reviewed to classify intraoperative factors: (1) medial rectus muscle attachment type (normal, abnormal [slipped or stretched scar], attached to pulley, behind pulley, or mixed [a tenuous normal attachment, but with muscle fibers also attached to the pulley or behind the pulley]), (2) medial rectus muscle distal fiber location (millimeters from original insertion), and (3) lateral rectus muscle tightness (normal, mild restriction, moderate restriction).

MAIN OUTCOME MEASURES

Relationship of grade of adduction deficit to each intraoperative factor.

RESULTS

Of 143 eyes, 124 (87%) had an adduction deficit. Eyes with abnormal (n = 23), pulley (n = 9), behind pulley (n = 8), or mixed (n = 7) attachments had worse adduction deficits than normal attachments (n = 96; P < 0.02). There was a significant correlation between distal medial rectus muscle fiber location (0-19.5 mm recessed) and grade of adduction deficit (P < 0.0001). Eyes with mild or moderate lateral rectus muscle tightness on forced duction testing (n = 48/143 eyes) had worse adduction deficits than eyes without tightness (P < 0.001). Nevertheless, despite overall correlation, there was considerable individual variability. For example, for -1 and -2 adduction deficits, medial rectus muscle attachment could be at the pulley, behind the pulley, or include the pulley (19/87 eyes [22%]), and the lateral rectus muscle was tight in 36 of 87 eyes (41%).

CONCLUSIONS

Adduction deficits are common in patients with consecutive exotropia. Overall, more severe preoperative adduction deficits are associated with medial rectus muscle insertion abnormalities and abnormal forced ductions, but frequently there are exceptions. Severe medial rectus muscle insertion abnormalities, including lost muscles, may be found despite mild preoperative adduction deficits.

Surgical results for consecutive exotropia

PURPOSE:

To evaluate the surgical results of medial rectus (MR) muscle advancement with or without recession of the antagonist muscle for consecutive exotropia.

METHODS:

Medical records of patients with consecutive exotropia (n = 27) were retrospectively reviewed. All patients received one-eye surgery with MR advancement, lateral rectus (LR) recession, or combined surgery. The pre- and post-operative angle of deviation was recorded. Characteristics were compared between groups. The follow-up period was at least 3 months.

RESULTS:

The overall successful rate was 62.96%, with 50% in MR advancement group, 60% in LR recession group, and 71.4% in combined group. Patients in combined group had larger preoperative deviation. There were comparable surgical results between patients with inferior oblique (IO) muscle overaction receiving correction simultaneously and patients without IO muscle overaction.

CONCLUSIONS:

The overall surgical successful rate for consecutive exotropia in this study was 62.96%. Combined MR advancement and LR recession yielded better results than MR advancement or LR recession alone although it was not statistically significant.

Orbital surface coil imaging predicts surgical anatomy of medial rectus muscle in consecutive exotropia: a case report

A 51-year-old woman with consecutive exotropia after surgery for esotropia underwent magnetic resonance imaging (MRI) of her orbits by orbital surface coil. Imaging demonstrated an 8.0 mm segment of very thin tissue that spanned the distance from a normal-looking medial rectus muscle proximally to the sclera distally. Surgical treatment revealed anatomic pathology of the medial rectus muscle consistent with spatial relationships of stretched scar and muscle that were predicted by MRI.

Clinical risk factors for the development of consecutive exotropia: a comparative clinical study

AIM

To compare a group of patients with consecutive exotropia with patients who had ≤10 prism diopters (PD) esotropia or no deviation postoperatively in terms of probable clinical risk factors for the development of consecutive exotropia.

METHODS

The study recruited fourteen patients who developed consecutive exodeviation during follow-up period after the correction of esotropia who were categorized as group 1 and thirty-one patients who had still ≤10 PD esotropia or no deviation at the final visit that were considered as group 2. Clinical risk factors leading the development of consecutive deviation were analyzed as the main outcome measures.

RESULTS

The mean age of patients was 4.57±3.11y in group 1 and 5.10±3.52y in group 2 (P=0.634). There was no significant difference of preoperative near and distant deviations among two groups (P=0.835, 0.928 respectively). The mean amount of medial rectus recession and lateral rectus resection was similar in both groups (P=0.412, 0.648 respectively). Convergence insufficiency and neurological diseases were more frequent in group 1 (P=0.007, 0.045). Accompanying neurological disease was found to be as a significant factor increasing the risk of the development of consecutive exotropia significantly [odds ratios (OR): 5.75 (1.04-31.93)].

CONCLUSION

Accompanying neurological disease appears to be a significant clinical risk factor for the development of consecutive exodeviation during postoperative follow-up after the correction of esotropia. However, larger studies are needed in order to interpret the results to the clinical practice and to ascertain other concurrent risk factors.

Classifying medial rectus muscle attachment in consecutive exotropia

PURPOSE

To evaluate interexaminer agreement in classifying medial rectus muscle attachment in patients with consecutive exotropia.

METHODS

A series of intraoperative photographs of 26 eyes in 25 patients who underwent surgery for consecutive exotropia were retrospectively studied. Two examiners independently classified the medial rectus attachment as either normal, stretched scar, slipped muscle, or lost muscle. Agreement between examiners was evaluated using the weighted kappa (κ) statistic, and causes of disagreement were assessed.

RESULTS

Agreement was found in 15 of 26 eyes (58%), signifying "moderate" agreement (κ = 0.41). Approximately two-thirds of the disagreements, 7 of 11 eyes (64%), were between stretched scar and slipped muscle, with characteristics of each entity being present in the same muscle.

CONCLUSIONS

The clinical distinction between stretched scar and slipped muscle appears to be obscure. We propose that they should be considered a single entity, which could be referred to as "abnormal scleral attachment."

Complications of Strabismus Surgery

All surgeries carry risks of complications, and there is no way to avoid ever having a complication. Strabismus surgery is no different in this regard. There are methods to reduce the risk of a complication during or after surgery, and these steps should always be taken. When a complication occurs, it is important to first recognize it and then manage it appropriately to allow for the best outcome possible. This article will discuss some of the more common and/or most devastating complications that can occur during or after strabismus surgery as well as thoughts on how to avoid them and manage them should they happen.

Complications of strabismus surgery: incidence and risk factors

PURPOSE

To perform a systematic review of the complications of strabismus surgery, focusing on incidence and risk factors.

MATERIAL AND METHODS

A systematic literature search was performed using the Medline and Cochrane databases.

RESULTS

Local complications, such as conjunctival injection and mild scarring, are almost universal but only rarely have long-term clinical significance. There are several important complications that are uncommon but associated with significant long-term sequelae, including slipped muscles, lost muscles, stretched scars, incarcerated muscles, pulled-in-two syndrome, periocular infections, orbital cellulitis, scleral perforations, retinal detachments, endophthalmitis, anterior segment ischemia, and surgical errors.

DISCUSSION

Strabismus surgery is associated with a number of common and serious complications, and it is important for both surgeons and patients to be aware of the risks.

Consecutive exotropia: why does it happen, and can medial rectus advancement correct it?

PURPOSE

To investigate whether consecutive exotropia following medial rectus muscle recession is associated with muscle slippage and to assess the effectiveness of treating the condition with medial rectus advancement.

METHODS

The records of patients with consecutive exotropia after medial rectus recession were reviewed to determine medial rectus muscle insertion location at the time of advancement surgery. Measurements before and after medial rectus advancement were compared. Success was defined as alignment within 10(Δ) of orthotropia. The dose effect of medial rectus advancement was determined by nonlinear regression.

RESULTS

A total of 20 patients were included. The mean age (± standard deviation) at time of surgery was 19 ± 19 years (range, 1.1-65.4). The mean preoperative exotropia was 28(Δ) ± 16(Δ) (range, 12(Δ)-60(Δ)). Medial rectus slippage of 2.5 ± 1.7 mm (range, 1.0-5.0 mm) was found in 14 patients (36%) who had previously undergone medial rectus recession. Surgery corrected about 4(Δ) of exotropia per mm total medial rectus advancement. Although 95% of patients were aligned successfully immediately after surgery, averaging 2(Δ) ± 4(Δ) esotropia, there was significant late exodrift, averaging 17(Δ) at final follow-up. At final follow-up, 1.6 ± 1.8 (range, 0.10-6.2) years after surgery, 50% of patients maintained alignment within 10(Δ) of orthotropia (mean, 3(Δ) ± 4(Δ) exotropia); the rest experienced recurrent exotropia of 25(Δ) ± 8(Δ).

CONCLUSIONS

Medial rectus slippage is common in consecutive exotropia. Medial rectus advancement effectively treated consecutive exotropia, whether or not there was muscle slippage. It is however, associated with late exodrift; hence patients should be warned about potential for further XT recurrence.

Changes in sagging extraocular muscle following surgical recession of the superior rectus muscle in rabbit eyes

PURPOSE

To verify whether central muscle sag actually induces excessive recession after recession of the rectus muscle in rabbit models.

METHODS

Twenty-four eyes of 12 rabbits were divided into two groups. In the right eyes (the muscle sagging group), half of the width of the original insertion was used to create a scleral suture during a 4-mm superior rectus muscle (SRM) recession and a central muscle sag of 2 mm was generated. Conventional 4-mm SRM recessions were performed in the left eyes (control group). At postoperative weeks 1, 2, and 4, the distances between the locations of the new insertion and the original insertion were measured at the center and nasal and temporal poles.

RESULTS

At postoperative week 4, the difference between the two groups at center was 1.38 ± 1.17 mm (P = .008). The mean extent of the recession at the nasal edge of the insertion was 5.21 ± 0.94 mm in the muscle sagging group, which showed posterior migration and slippage relative to the mean extent of the recession in the control group (4.29 ± 0.50 mm; P = .014). The mean extent of the recession at the temporal edge of the insertion was 5.50 ± 0.74 mm in the muscle sagging group and 4.50 ± 0.77 mm in the control group (P = .005).

CONCLUSIONS

Overcorrection that occurred in cases of central muscle sag in the rabbit models resulted from posterior migration of recessed muscle that occurred in conjunction with slippage of its nasal and temporal edges.

Incomitant strabismus: does extraocular muscle form denote function?

The paradigm that an underacting extraocular muscle (EOM) is always atrophic or hypoplastic, and an overacting EOM should always be enlarged, leads to inconsistencies with clinical observations. It is inconsistent with the findings of normal extraocular muscle diameters in patients with apparent superior oblique muscle palsy, "overacting" inferior oblique muscles, and the superior rectus muscle overaction / contracture syndrome, among other clinical entities. These inconsistencies can be reconciled if one accepts the possibility that EOM contractile activity may reflect a change in neural input to an anatomically normal muscle, and / or that muscle contractile activity may be altered by a shift in fiber type and distribution within a normal-sized muscle. This remodeling may occur as a result of vergence adaptation or any change in neural stimulus to the muscle. There is substantial evidence to suggest that both these theoretical possibilities may likely occur.

Three horizontal muscle surgery for large-angle infantile esotropia: validation of a table of amounts of surgery

PURPOSE

To validate a table of amounts of three horizontal muscle surgery in patients with large-angle infantile esotropia (≥60 prism dioptres, PD).

METHODS

A prospective interventional case series reporting the postoperative alignment of 51 patients (27 male, 24 female) over a 15-year period was conducted. Surgery amounts were according to a published table developed on a previous patient cohort (n=49), using bilateral medial rectus recession with graded unilateral lateral rectus resection. Kaplan-Meier life-table survival curves were formulated for success to orthotropia (±10 PD) after one and subsequent horizontal muscle surgeries for up to 8 years follow-up.

RESULTS

The median preoperative deviation was 65 PD (range 60-80 PD) and median age at surgery was 11.8 months (range 5.1 months-3.6 years). Surgical success to orthotropia (±10 PD) after one surgery was 100% at 2 months, 95.7% at 6 months, 91.3% at 12 months, 77.8% at 4 years, and 73.6% at 8 years. Postoperative failure requiring further horizontal surgery occurred in 17.6% (residual esotropia 4, consecutive exotropia 5).

CONCLUSIONS

Our second cohort has reproduced the success rate of the previous cohort (77.8% vs 77.1% at 4 years). If the published table of surgical amounts is used, three horizontal muscle surgery in large-angle infantile esotropia (≥60 PD) appears to have a good long-term success rate, and does not lead to the high rates of either residual esotropia or consecutive exotropia reported by others in the literature.

Efficacy of marlex mesh on posterior fixation suture: an experimental study in a rabbit model

PURPOSE

To develop a novel method of posterior fixation suture augmented by the application of Marlex mesh and to evaluate the surgical results in a rabbit model.

DESIGN

Animal study.

METHODS

SETTING

Prospective, masked-observer, controlled experimental study.

STUDY POPULATION

Sixty superior rectus muscles of 30 rabbits.

INTERVENTION

Each superior rectus muscle was randomly subjected to posterior fixation suture at a distance of 6 mm from the muscle insertion. The rabbits were divided into 3 groups: conventional posterior fixation suture (Conventional group), and modified posterior fixation suture using a silicone sponge (Silicone group) or using Marlex mesh (Marlex group). Nonabsorbable sutures were used for muscle-sclera (Conventional group) or muscle-implant fixation (Silicone and Marlex group) and absorbable sutures were used for implant-sclera fixation (Silicone and Marlex group).

MAIN OUTCOME MEASURES

The efficacy of posterior fixation suture was determined by forced duction testing toward the operated-on muscle immediately after the operation and at 8 weeks postoperatively. Eyes were enucleated at 8 weeks after surgery to measure the stability of the bond using a push pull gauge, and finally the histologic findings were evaluated.

RESULTS

Immediately after posterior fixation suture and at 8 weeks postoperatively, the restrictive motion during duction toward the operated-on muscle was greater in the Marlex group compared to the other groups (P < .001). The resistance to separation of the myoscleral union was greatest in the Marlex group (P < .001).

CONCLUSIONS

Posterior fixation suture can be effectively reinforced and stabilized using Marlex mesh.

A pilot study of the value of prism adaptation in planning strabismus reoperations

PURPOSE

To evaluate the value of prism adaptation in planning strabismus reoperations.

METHODS

Of 15 patients with persistent strabismus, 9 underwent prism adaptation prior to strabismus reoperation and 6 underwent strabismus reoperation without preoperative prism adaptation. Corrective surgery was performed on the same or new muscles. Follow-up ranged from 3 months to 2 years. A horizontal deviation of 10 prism diopters or less was considered a successful outcome. Statistical analysis of the results was done.

RESULTS

Of the 9 patients who had prism adaptation, 3 (33%) were responders and 6 (67%) were nonresponders. A successful outcome was achieved in 6 patients (67%) who had prism adaptation and 3 patients (50%) who did not. The difference between groups was statistically insignificant (P > .05).

CONCLUSION

These results suggest that the benefits of prism adaptation are not significant enough to justify the time consumption and expenses of this test when planning strabismus reoperations, but a larger group of patients should be studied.

Strabismus associated with thyroid eye disease

PURPOSE OF REVIEW

We discuss the evaluation and treatment of strabismus related to thyroid eye disease with special attention to the literature published in 2006.

RECENT FINDINGS

The etiology of thyroid eye disease is complex, although a recent review article evaluated the causative relationship between smoking and thyroid eye disease. The treatment of thyroid eye disease is also complex and involves a multidisciplinary approach including endocrinology and ophthalmology. Several recent articles have evaluated the role of medications in the treatment of thyroid eye disease. We discuss the current surgical strategies for the treatment of strabismus related to thyroid eye disease, including the use of adjustable suture techniques. New techniques in nonadjustable surgery are also examined.

SUMMARY

Strabismus related to thyroid eye disease presents many challenges to the ophthalmologist. Successful treatment of strabismus is rewarding however, and has a significant impact on improving a patient's quality of life.

Adjustment of the surgical nomogram for surgery on slipped extraocular muscles

PURPOSE

A slipped muscle is an underdiagnosed complication of strabismus surgery. Surgery necessitates intraoperative diagnosis, measurement, and resection of the empty sheath. We analyzed the results of empty sheath surgery for slipped medial and lateral rectus muscles in a large cohort of patients.

METHODS

Eighty-five patients who underwent empty sheath surgery at a secondary referral center by a single strabismologist were included in the study. We retrospectively analyzed the preoperative and postoperative change in angle of deviation 6 weeks after surgery. All cases were reoperations in which an unexpected or unsatisfactory outcome followed primary surgery. Consecutive exotropias with slipped medial rectus muscles were noted in 68 patients. There were 17 esotropia cases with lateral rectus muscles slip, of which 2 were consecutive exotropias that became consecutive esotropias. Bilateral medial rectus muscle slips were found in 6 patients with consecutive exotropias. Adjustable suture surgery was performed in 27 patients.

RESULTS

Resection of the empty sheath of the slipped medial or lateral rectus muscle with advancement to the original site of insertion was done in all cases; in addition, the antagonist muscle was recessed only if it was tight. The total muscle advancement was calculated in millimeters from the total amount of sheath resected, muscle advanced, and the antagonist recessed. The greater the preoperative deviation, the more surgical muscle advancement was required and the greater the change in postoperative angle of deviation. Mean change in angle of deviation was 3.13(delta) for each millimeter of muscle advancement (median = 3.00, SD = 1.72).

CONCLUSIONS

The diagnosis of slipped muscle should be confirmed during strabismus surgery. The empty sheath was measured, resected, and the muscle advanced to the original site of insertion. An approximate 3(delta) change in angle of deviation was observed for every millimeter of muscle of advancement. For very large and very small deviations, surgeons should modify this to an accustomed measurement dictated by their experience.

An evaluation of the semiadjustable suture strabismus surgical procedure

BACKGROUND

Muscle slippage is an adverse outcome of strabismus surgery. Its incidence is increased if adjustable sutures are used or if surgery is performed on the inferior or medial rectus muscles. Although there are no firm numbers for this complication, studies have suggested incidence rates between 7% and 41% when adjustable suture surgery is performed on the inferior rectus muscle. In theory, the semiadjustable suture procedure should decrease this adverse outcome. This procedure involves suturing the corners of the muscle firmly to the sclera and placing the center of the muscle on an adjustable suture. This study evaluates semiadjustable suture surgery with respect to muscle slippage.

METHODS

The primary treatment group consisted of 57 patients who underwent semiadjustable suture surgery on a total of 61 muscles that either had never previously undergone surgery or had undergone surgery and had not previously slipped postoperatively. Fifty-five were inferior rectus muscles and 6 were medial rectus muscles. An additional 7 patients had semiadjustable suture surgery on muscles that had slipped after prior surgery and were analyzed separately. The outcome evaluation was at least 6 months after surgery.

RESULTS

None of the 57 patients in the primary treatment group demonstrated muscle slippage after semiadjustable suture surgery. One of the 7 patients who had history of prior muscle slippage also had slippage after semiadjustable suture surgery.

CONCLUSION

The semiadjustable suture procedure appears to decrease the incidence of muscle slippage.