Ultrasound Biomicroscopy in Strabismus Surgery: Efficacy in Postoperative Assessment of Horizontal Muscle Insertions

Reliability of the Mendonça Strabismus Forceps in Locating the Insertion of Extraocular Rectus Muscles in Patients Undergoing Strabismus Surgery

PURPOSE

To evaluate the reliability of Mendonça strabismus forceps in locating the extraocular rectus muscles in patients undergoing primary strabismus surgery or reoperation. The study also compared the method's efficacy in primary surgeries versus reoperations. The overall goal was to avoid unnecessary surgical exploration, thereby enabling more effective planning and safer surgery.

METHODS

The study included 41 patients with strabismus undergoing surgical correction. The reliability of the Mendonça strabismus forceps in locating the extraocular rectus muscles was evaluated by comparing preoperative measurements using Mendonça strabismus forceps and Castroviejo forceps to intraoperative measurements made by direct muscle visualization. Differences of 1 mm or less were deemed acceptable.

RESULTS

In patients without prior surgery, Mendonça strabismus forceps reliably located all muscles, with measurements consistently within the 1-mm limit. All muscles with previous surgeries were successfully grasped by the forceps, except for one medial rectus muscle with multiple interventions. In reoperations with satisfactory muscle grasp, 88.8% showed coincident measurements. Non-coincidence cases were attributed to anomalous scarring. The method demonstrated simplicity, cost-effectiveness, and no complications in this study.

CONCLUSIONS

The Mendonça strabismus forceps proved to be a reliable and non-invasive method for locating extraocular rectus muscles insertions without the need for additional imaging. It is a cost-effective, simple, and easily executed method that provides valuable information for surgical decision-making and planning. The method enhances surgical outcomes while reducing risks. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XX-XX.].

Comparison of anterior segment optical coherence tomography and ultrasound biomicroscopy in localizing horizontal rectus muscle insertions

PURPOSE

To evaluate the viability and precision of measuring the distance from the limbus to extraocular muscle insertion using anterior segment optical coherence tomography (AS-OCT) and panoramic ultrasound biomicroscopy (UBM) before and after strabismus surgery.

METHODS

We recruited primary strabismus patients and measured the limbus-insertion distance by AS-OCT and UBM preoperatively, 2 weeks, and 1, 3, and 6 months postoperatively. Values were also measured using callipers intraoperatively before and after the planned procedures. Preoperative AS-OCT and UBM values were compared to intraoperative calliper measurements as the gold standard. Postoperative AS-OCT and UBM values were compared to the new postoperative limbus-insertion distance. The limit of agreement deemed clinically acceptable was defined as 1 mm.

RESULTS

A total of 85 horizontal muscles of 40 patients, including 48 lateral rectus muscles and 37 medial rectus muscles, were analysed. Primary muscles could be successfully detected by AS-OCT (95%) and UBM (100%). At 2 weeks and 1, 3, and 6 months postoperatively, the new rectus muscle attachment site detection rate by AS-OCT was 6%, 32%, 80%, and 89%, respectively, and that by UBM was 24%, 60%, 85%, and 93%, respectively. The Bland-Altman plots revealed better consistency in pairs of AS-OCT, UBM, and calliper measurements of primary muscles than postoperative muscles. For primary muscles, 89% of AS-OCT measurements fell within the permissible range of surgical measurements (1 mm), but this dropped to 67% at 6 months postoperatively (P < 0.001). The accuracy of UBM measurements of primary muscles was 81%, and this decreased to 59% at 6 months postoperatively (P = 0.001).

CONCLUSIONS

AS-OCT and UBM performed well in terms of imaging primary horizontal rectus muscles, but showed decreased accuracy and reproducibility in postoperative muscle measures.

Efforts to improve the surgical outcome for exotropia and investigation of the insertion locations of the extraocular muscles

In our previous retrospective study, we found that using the strabismus surgery dosages established by western strabismus mentors tends to result in undercorrection of Taiwanese exotropia (XT) patients compared with those in western populations. We also discovered that the location of extraocular muscle (EOM) insertion could vary by ethnicity. In this study, using a generalized estimation equation model, we compared the XT surgery outcome between augmented and original strabismus surgery dosages in Taiwanese patients. We also conducted an observational study to investigate the horizontal EOM insertion location in a Taiwanese population and compared the data with Dr. Apt L.'s study. For Taiwanese XT patients, augmented surgical dosages resulted in significantly better outcome at 6 months and 1 year postoperatively compared with original surgical dosages (p = 0.003 and p < 0.001, respectively). The distance from the lateral recuts muscle (LR) insertion location to the limbus was significantly shorter in Taiwanese than in white Americans (6.5 vs. 6.9 mm, respectively, p = 0.0001). Furthermore, the medial rectus muscle and LR insertion locations differed significantly between males and females (p < 0.001 and p = 0.023, respectively). The patients' sex did not affect the surgery outcome. Augmented surgery doses modified from western strabismus mentors produce better surgery outcome for Taiwanese XT patients. Surgeons may require country-specific guidelines for strabismus surgery dosage. We also demonstrated a simple method for young ophthalmologists to establish their own normograms to improve their surgical success rate. Our study confirms that LR insertion locations differ between Taiwanese and White Americans.

Clinical Role of Swept Source Anterior Segment Optical Coherence Tomography in Strabismus Re-Operation with Lost Surgical Details

Background

To characterize the diagnostic role of swept source anterior segment optical coherence tomography (SS-ASOCT) in strabismus re-operations with lost surgical details.

Methods

Patients presenting to our outpatient services for strabismus care from February 2020 to March 15th 2021 were systematically evaluated. Those willing to undergo re-operation were included in the study. A total of 30 patients were identified and out of this a total of 10 eyes of 10 patients with lost surgical details were finally included in the study. Demographic details, preoperative deviation, ocular findings, orthoptic measurements, detailed SS-ASOCT findings, intraoperative measurements, and post-operative outcomes were recorded.

Results

The mean age of 10 patients was 23.7±5.75 years. Seven were male and three were female. The mean pre-operative SS-ASOCT measured distance from angle to insertion was 8.90±1.85 mm and the mean intraoperative distance was 9.12±2.14 mm. A mean difference of 0.21±1.31 mm was noted, and this difference was statistically insignificant (paired t test, p = 0.57). In addition, SS-ASOCT unraveled novel signs to differentiate operated eyes from the un-operated eyes, and recessed muscle from the resected muscle.

Conclusion

In strabismus re-operation with lost surgical details, the pre-operative SS-ASOCT can provide reliable muscle details with respect to its type of surgery and amount surgery.

Comparison of the swept-source anterior segment optical coherence tomography and wide-field ultrasound biomicroscopy for imaging previously operated horizontal extraocular muscles

PURPOSE

To assess the feasibility and accuracy of determining extraocular muscle insertion distance from the limbus of previously operated extraocular muscles with the swept-source anterior segment optical coherence tomography (AS-OCT) compared with wide-field ultrasound biomicroscope (UBM).

METHODS

Patients with a history of previous strabismus surgery for whom additional strabismus surgery was planned were enrolled. The insertion distance was measured by AS-OCT and UBM before reoperation and compared to the caliper measurement at the time of surgery. Observers taking measurements were masked to patient data. Patient comfort for both machines was graded on a scale of 1-10 and timing of both imaging procedures was recorded.

RESULTS

Thirteen previously operated muscles of 6 subjects (age 20.3 ± 4.4 years; range, 11-25) were imaged. The muscle insertion could be identified in 12 cases on AS-OCT and 10 cases on UBM. The difference between the imaging result and the caliper reading was ≤1 mm in 9 cases on AS-OCT and 5 cases on the UBM (69% vs 38%; P = 0.03). The maximum insertion distance on AS-OCT was 13.8 mm; on UBM, 10.4 mm. AS-OCT had a higher grade than UBM for patient comfort (P = 0.0005) and speed (P = 0.001).

CONCLUSIONS

In our cohort, AS-OCT identified the muscle insertion distance more accurately than UBM. AS-OCT measurements were judged more comfortable to the patient, and images were acquired faster. In large recessions, wide-field UBM yields suboptimal results compared with AS-OCT.

Ultrasound biomicroscopy in ophthalmology

This review presents data on the use of the method of ultrasonic biomicroscopy (UBM) of the anterior segment of the eye in ophthalmological practice in adults and children. Ultrasound biomicroscopy (UBM) is a contact non-invasive method for visualizing structures of the anterior segment of the eye using high-frequency ultrasound in the range from 35 to 100 MHz. Literature data indicate that UBM can be used to visualize almost all structures of the anterior segment, including the cornea, iridocorneal angle, anterior chamber, iris, ciliary body and lens, as well as the peripheral parts of the retina, vasculature and vitreous. There is data on the use of this method in the study of pathogenetic aspects of glaucoma, pseudoecfoliative syndrome, various types of cataracts, post-traumatic injuries of the anterior segment of the eye, meimobium gland dysfunction and other ophthalmopathologies. The use of UBM in children, due to the peculiarities of its implementation, is not widespread, but due to the specificity of the data obtained using it, it is promising. The limited information about the use of UBM in retinopathy of prematurity and the diagnostic capabilities of the method makes its use especially relevant in this severe retinal disease of premature newborns.

A systematic review of ultrasound biomicroscopy use in pediatric ophthalmology

Ultrasound biomicroscopy (UBM) is the only available option for noninvasive, high-resolution imaging of the intricate iridociliary complex, and for anterior segment imaging with corneal haze or opacity. While these unique features render UBM essential for specific types of trauma, congenital anomalies, and anterior segment tumors, UBM imaging has found clinical utility in a broad spectrum of diseases for structural assessments not limited to the anterior intraocular anatomy, but also for eyelid and orbit anatomy. This imaging tool has a very specific niche in the pediatric population where anterior segment disease can be accompanied by corneal opacity or clouding, and anomalies posterior to the iris may be present. Pediatric patients present additional diagnostic challenges. They are often unable to offer detailed histories or fully cooperate with examination, thus amplifying the need for high-resolution imaging. This purpose of this systematic review is to identify and synthesize the body of literature involving use of UBM to describe, evaluate, diagnose, or optimize treatment of pediatric ocular disease. The collated peer-reviewed research details the utility of this imaging modality, clarifies the structures and diseases most relevant for this tool, and describes quantitative and qualitative features of UBM imaging among pediatric subjects. This summary will include information about the specific applications available to enhance clinical care for pediatric eye disease.

Accuracy of anterior segment optical coherence tomography for pre-operative localization of insertions of extraocular recti muscles

Introduction:

To study the accuracy of anterior segment optical coherence tomography (AS-OCT) function of Cirrus HD-OCT 500 (Carl Zeiss Meditec, Dublin, CA) in calculating the insertion of rectus muscles from the limbus in patients undergoing primary squint surgery.

Methodology:

A prospective, double-masked, observational study was conducted on 128 muscles of 46 patients with strabismus who were planned for strabismus surgery between January 2019 and December 2019. Insertion distance from limbus was measured using AS-OCT function of Cirrus HD-OCT 500 preoperatively. Intraoperative measurements were taken using Castroviejo caliper. A Bland-Altman analysis was performed to determine the agreement between the readings.

Results:

A total of 128 muscles were successfully imaged and evaluated, including 13 superior recti (10.15%), 23 inferior recti (17.96%), 35 medial recti (27.34%) and 57 lateral recti (44.53%). 124 muscles (96.9%) were within 1mm difference, which was considered clinically acceptable. Bland-Altman plots showed the level of agreement between the two methods was good.

Conclusion:

Anterior segment scan function of Cirrus HD-OCT 500 is an accurate method to detect the insertion of extraocular recti muscles in patients of primary strabismus surgery.

Extraocular muscle insertion shift after disinsertion during strabismus surgery

PURPOSE

To quantify the amount of insertion shift after disinsertion of the rectus muscles and identify factors that may influence the shift.

METHODS

Patients who underwent rectus muscle surgery between November 2018 and April 2019 were included. During surgery, the limbal-insertion distance (LID) distance was measured in millimeters with calipers from the limbus to the center of the insertion at the anterior border of the rectus muscle prior to and after disinsertion. The primary outcome was the shift of the rectus muscle insertion after disinsertion. This was calculated by subtracting the LID after disinsertion from the LID before disinsertion. The secondary outcome was the identification of preoperative and intraoperative factors that influenced insertion shift. Randomization was performed to select one rectus muscle per patient. Patients with a history of prior scleral buckle procedure, glaucoma drainage device, orbital wall fracture and strabismus surgery in the same rectus muscle were excluded.

RESULTS

110 patients were included. The median (Q₁, Q₃) LID before disinsertion was shortest for the medial rectus muscle [5.0 (4.5, 6.0)], followed by lateral rectus muscle [6.0 (6.0, 7.0)] and inferior rectus muscle [6.0 (5.5, 7.0)]. The overall median (Q₁, Q₃) insertion shift was 1.0 (0.8, 1.0) mm (p < .001), which did not significantly differ between each rectus muscle subgroup (p = .158). Factors that influenced the amount of shift were moderate to severe restriction on forced duction testing (FDT) (B = 0.320, SE = 0.105, p = .003) and longer LID before disinsertion (B = 0.172, SE = 0.036, p < .001).

CONCLUSIONS

We found a significant anterior insertion shift after disinsertion of rectus muscles. Moderate to severe restriction on FDT and longer LID before disinsertion can result in larger insertion shifts.

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.].

Comparison of plication and resection in large-angle exotropia

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 30^Δ-50^Δ 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 = 0.81) and abduction limitation (P = 0.169). UBM could identify and quantify plication in all cases with excellent agreement with the operative data (intraclass correlation coefficient = 0.886; P = 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.

The accuracy of wide-field ultrasound biomicroscopy in localizing extraocular rectus muscle insertions in strabismus reoperations

PURPOSE

To compare the accuracy of widefield ultrasound biomicroscopy (UBM) with mechanical intraoperative measurements of the distance between rectus muscle insertions and the corneal limbus in strabismus reoperations.

METHODS

Subjects with a history of horizontal rectus muscle surgery who required further surgery on horizontal rectus muscle(s) were recruited prospectively. All widefield UBM measurements were carried out under topical anesthesia using a 50 MHz linear probe without immersion cup and external caliper. The insertion angle distance was measured using the caliper tool of the UBM device; the actual muscle insertion distance from the limbus was considered to be the measured distance plus 1 mm. The distance from muscle insertion to the limbus was also measured intraoperatively. The results of UBM and surgical measurements were compared.

RESULTS

A total of 28 subjects were recruited, and 53 horizontal muscles (30 medial rectus, and 23 lateral rectus muscles) were included. The longest distance of the muscle insertion from limbus detectable on UBM was 13 mm for the medial rectus muscle and 15 mm for the lateral rectus muscle. In 38 muscles (71.7%) UBM and surgical measurements were within 1 mm of each other. Only in 1 muscle (1.9%) was the difference between measurements >2 mm (2.3 mm). The intraclass correlation coefficient was 0.87, demonstrating excellent agreement between measurements. Limit of agreement analysis demonstrated better agreement between measurements of medial rectus muscles and in consecutive exotropia cases.

CONCLUSIONS

This study demonstrated good agreement between intraoperative and widefield UBM measurements of the muscle insertion-limbus distance in our patient cohort.

The role of imaging in strabismus

PURPOSE OF REVIEW

To review the most recent literature regarding the clinical experience of imaging modalities in strabismus.

RECENT FINDINGS

MRI of extraocular muscles (EOMs) has elucidated the roles of variation in compartmental contraction of EOMs and further evidence of EOM pulley heterotopy in various strabismus patterns, which may contribute to the clinical and surgical management of patients as this mode of imaging becomes more readily available. Ultrasound biomicroscopy (UBM) and anterior-segment optical coherence tomography (AS-OCT) may play a role in determining the location of EOMs which could also aid in devising a preoperative surgical plan, especially in those who have had prior strabismus surgery.

SUMMARY

Although MRI, UBM, and AS-OCT show promise in the formulation of a treatment plan in complex strabismus, more research regarding the role and limitations of these imaging modalities is required before they become the mainstay of strabismus evaluation.

Accuracy of Optical Coherence Tomography Measurements of Rectus Muscle Insertions in Adult Patients Undergoing Strabismus Surgery

PURPOSE

To assess the accuracy of anterior segment optical coherence tomography (AS-OCT) in measuring the distance of extraocular muscle (EOM) insertion to the limbus to improve preoperative assessment of adult patients undergoing strabismus surgery.

DESIGN

Reliability analysis.

METHODS

setting: An institutional practice.

PATIENT POPULATION

Seventy-four adult patients scheduled for strabismus surgery on rectus muscles.

OBSERVATION PROCEDURE

The distance between the EOM insertion and the limbus was measured preoperatively with AS-OCT. The value was compared with the intraoperative measurement obtained with calipers. Additional measurements included the limbus-anterior chamber angle distance with AS-OCT and the axial length with IOLMaster.

MAIN OUTCOME MEASURE

Agreement between preoperative AS-OCT and intraoperative measurements. A difference of ≤1 mm was "clinically acceptable."

RESULTS

A total of 144 muscles were analyzed. Thirty-one of 33 reoperated muscles were successfully imaged. AS-OCT measurements were within 1 mm of intraoperative measurements in 77% of all muscles. The accuracy was higher for muscles with no prior surgery (83%), as compared with reoperated muscles (58%). Although the accuracy decreased when comparing reoperations to primary surgeries for the medial (79% to 63%; P = .09; 95% confidence interval [CI], -1.38 to 0.11) and the lateral rectus (81% to 49%; P = .11; 95% CI, -2.06 to 0.22), the difference was not significant. No correlation between limbus-anterior chamber angle distance and axial length was established.

CONCLUSIONS

AS-OCT is valuable in identifying EOM insertions in primary strabismus surgeries, but the accuracy decreases in reoperations.

Future of the Renal Biopsy: Time to Change the Conventional Modality Using Nanotechnology

At the present time, imaging guided renal biopsy is used to provide diagnoses in most types of primary and secondary renal diseases. It has been claimed that renal biopsy can provide a link between diagnosis of renal disease and its pathological conditions. However, sometimes there is a considerable mismatch between patient renal outcome and pathological findings in renal biopsy. This is the time to address some new diagnostic methods to resolve the insufficiency of conventional percutaneous guided renal biopsy. Nanotechnology is still in its infancy in renal imaging; however, it seems that it is the next step in renal biopsy, providing solutions to the limitations of conventional modalities.