Identification and biometry of horizontal extraocular muscle tendons using optical coherence tomography

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.

Anterior segment optical coherence tomography in ocular surface tumours and simulating lesions

This study aims to systematically review the reported literature on the use of anterior segment optical coherence tomography (AS-OCT) in ocular surface tumours and simulating lesions. A systematic literature search was done using PubMed, Scopus, and Web of Science databases between January 2002 and December 2021. On AS-OCT, ocular surface squamous neoplasia typically demonstrate epithelial thickening, epithelial hyperreflectivity, and an abrupt transition between normal and abnormal epithelium. Conjunctival nevi usually show mildly hyperreflective epithelium of normal thickness, internal hyperreflectivity, and intralesional cysts which is the hallmark of this tumour. Primary acquired melanosis presents with normal thickness epithelium, basal epithelial hyperreflectivity, and absence of cysts. Conjunctival melanoma demonstrates hyperreflective normal/thickened epithelium, hyperreflective basal epithelium, internal hyperreflectivity, and absence of intralesional cysts. Conjunctival lymphoma shows homogenous, low-medium reflective subepithelial lesions with smooth borders, and dot-like infiltrates. Benign reactive lymphoid hyperplasia findings are similar to lymphoma but the infiltrates are more hyperreflective compared to lymphoma. Pterygium shows thickened conjunctival epithelium, epithelial hyperreflectivity, and subepithelial wedge-shaped hyperreflective tissue separated from the overlying epithelium by a cleavage plane. Pinguecula demonstrates mildly thickened epithelium and similar findings with pterygium but does not extend beyond the corneal limbus. This review shows that AS-OCT, as a noninvasive tool, has potential uses in the differential diagnosis of ocular surface tumours and simulating lesions. Major limitations of AS-OCT include limited visualization of the posterior border of thick, keratinized, and pigmented tumours and lack of assessment of large conjunctival tumours in a single cut.

In vivo analysis of ciliary muscle in myopic Chinese young adults using ArcScan Insight® 100

OBJECTIVE

To analyse the morphological characteristics of the ciliary muscle (CM) and to explore its relationship with different ocular biometric parameters in myopic young Chinese adults.

METHODS

This observational, cross-sectional study included 50 right eyes from 50 myopic adults. The CM area (CMA), CM thickness (CMT) and CM length (CML) were measured using the ArcScan Insight^® 100. CMT was determined at three points: 1.0 mm (CMT-1), 2.0 mm (CMT-2) and 3.0 mm (CMT-3) posterior to the scleral spur. CML was measured on the scleral (CMLs) and vitreous (CMLv) aspects. The spherical equivalent refraction (SER), axial length (AL) and subfoveal choroidal thickness (SFCT) were examined to determine their associations with CM parameters (CMA, CML and CMT).

RESULTS

The mean SER and AL were -4.39 ± 2.29 D and 25.61 ± 1.15 mm, respectively. Compared with the nasal CMA, CML and CMT (CMT-1, CMT-2 and CMT-3) findings, the temporal CM parameters (CMA, CMLs, CMLv, CMT-1, CMT-2 and CMT-3) were found to be significantly thicker (all p < 0.001, except CMLv and CMT-1; p < 0.01). The nasal CMA was associated with the average corneal curvature (r = 0.30, p = 0.03) and SER (r = -0.30, p = 0.04). Nasal and temporal CMT-2 were negatively correlated with SER (r = -0.33 and -0.32, respectively, both p < 0.05). There was no correlation between CM parameters (except nasal CMLs, r = 0.31, p = 0.03) and SFCT, or between CM parameters and either the AL or anterior chamber depth (all p > 0.05).

CONCLUSION

These results suggest that there is temporal versus nasal asymmetry of the CM. CMA, CMT or CML did not vary with axial growth of the eye. The CM is not simply stretched as the eye elongates in myopic young adults.

Correlation between Thyroid-stimulating Antibody Level Change and Extraocular Muscle Thickness Change in Thyroid Eye Disease

Purpose: To investigate the changes in extraocular muscle thicknesses by variations in the thyroid stimulating antibody (TSAb) level in patients with thyroid eye disease (TED).Methods: A total of 67 TED patients were enrolled. They were divided into two groups: an experimental group with clinically significant elevated TSAb levels (≥140 IU/L) and a control group (TSAb <140 IU/L). All of the lateral, medial, superior, and inferior rectus muscle thicknesses were measured with the aid of anterior segment optical coherence tomography (OCT). The average thicknesses for both eyes were recorded for each patient based on the values measured at the ends of the muscles (which become vertically thinner from the points of tendon attachment). We measured changes in TSAb levels and extraocular muscle thicknesses after two follow-up periods and sought correlations among these parameters.Results: At the initial visits, the inferior rectus muscle thickness was positively correlated with the TSAb level in the experimental group (p = 0.045, r = 0.478). None of the medial, superior, or lateral rectus muscle thicknesses were so correlated. On follow-up, the variation in TSAb level correlated negatively with changes in lateral rectus muscle thickness (p = 0.038, r = -0.357). The superior rectus muscle thickness tended to be negatively correlated with the TSAb level, but statistical significance was not attained (p = 0.146, r = -0.669). The thicknesses of the inferior and superior rectus muscles did not change over time.Conclusions: In TED patients, TSAb variations seem to reflect the extent of periorbital tissue edema, thus correlating negatively with especially lateral rectus muscle thickness changes.

Evaluation of the insertion distance of the medial rectus in consecutive exotropia by means of intraoperative measure and optical coherence tomography

PURPOSE

To assess the agreement between the measurements of the distance from the medial rectus muscles insertion to the limbus measured by intra-operative spectral-domain optical coherence tomography (SD-OCT) in consecutive exotropia (cXT).

METHODS

An analysis was performed on total of 14 medial rectus (MR) muscles of 14 patients who underwent surgery for the treatment of cXT. The limbus-insertion distance of the MR muscles was measured using preoperative SD-OCT and intraoperatively using a calliper. The intraclass correlation coefficient (ICC) and Bland Altman plots were calculated to determine the agreement between the two methods, as well as the correlation.

RESULTS

Mean age was 36.3 ± 16.0 years (range 13-60), with 60% being women. Mean preoperative deviation was 38.7 ± 16.9 prismatic dioptres (PD) (range 16-65), being +1.3 ± 6.3 PD (range -12 to +10 PD) after surgery. Intraoperatively the MR insertion was found at 8.7 ± 2.1 mm (range 5.5-12.0) and by OCT at 7.7 ± 1.2 mm (range 5.3-10.0). The ICC showed a moderate to good agreement (0.659; 95% confidence interval: 0.157-0.885; p < 0.001), with a correlation of R = 0.792 (p = 0.011). A better agreement was observed in those MR that were less retro-inserted.

CONCLUSIONS

SD-OCT is able to measure the insertion to the limbus distance of the medial rectus muscles that have been previously operated on, showing moderate to good agreement with intraoperative measurements. However, the agreement was poor in muscles with a large retro-insertion.

Do rectus muscle parameters vary between emmetropes and myopes?

PURPOSE

This study investigated the thickness, area, and insertion site of the medial (MR) and lateral (LR) rectus muscles in individuals with emmetropia and different degrees of myopia.

METHODS

Swept-source optical coherence tomography images of the MR and LR muscles in 80 participants including emmetropes (spherical equivalent refractive error [SER] ±0.50 D, N = 14) and myopes (≤ -0.75 D, N = 66), were analysed. Custom-designed, semi-automated software was used to measure parameters such as insertion distance from limbus, muscle thickness at every 1 mm interval to 3 mm periphery and muscle area from insertion site to 3 mm.

RESULTS

The median (Q1, Q3) SER error and axial length were -6.00 D (-13.25, -2.12) and 25.78 mm (23.78, 28.61), respectively. The MR was significantly thinner (mean ± SE: 137.7 ± 8.9 vs. 159.7 ± 8.9 µm, p < 0.01) and occupied less area than the LR (0.35 ± 0.01 vs. 0.42 ± 0.01 mm² , respectively, p < 0.01). The thickness of the MR gradually increased from the insertion site to a 3 mm peripheral eccentric location (106.5 3.8 µm at 1 mm, 135.5 ± 4.5 µm at 2 mm and 156.1 ± 5.9 µm at 3 mm, p < 0.01). The overall median thickness of the MR was significantly less in myopes (129 µm [111.5, 152.2]) than emmetropes (158.1 [134.3, 167.7] µm, p = 0.03). However, no such trend was seen in the LR muscle. Muscle area and insertion distance were not different between emmetropes and myopes in both horizontal rectus muscles.

CONCLUSION

Unlike the LR, the parameters of the MR (thin and occupying less area) show significant association with myopia. While the key finding of this study indicates the possible association of MR parameters with myopia, the clinical relevance of this finding and its role in myopiogenesis/progression needs to be investigated further.

Effects of the Gaze Fixation Position on AS-OCT Measurements of the Limbus and Extraocular Muscle Insertion Site Distance

PURPOSE

To investigate the effect of the gaze fixation position on measurement of the limbus and extraocular muscle (EOM) insertion site distance using anterior segment optical coherence tomography (AS-OCT).

METHODS

Patients undergoing horizontal EOM surgeries were enrolled in this prospective experimental study. The distance between the angle recess and the muscle insertion site was measured using AS-OCT while patients fixed their gaze laterally or medially at inner or outer gaze fixation. The distance between the limbus and muscle insertion was intraoperatively measured using calipers.

RESULTS

A total of 46 lateral rectus muscles and 36 medial rectus muscles of 44 patients were evaluated. Significant differences were observed between intra-operative measurements (6.3 ± 0.7 mm) and AS-OCT measurements (5.8 ± 0.7 mm) for the lateral rectus muscle at inner gaze fixation (P = .0017) and medial rectus muscle at outer gaze fixation (P = .0003); no difference was observed when the lateral rectus (6.4 ± 0.5 mm) and medial rectus (4.9 ± 0.6 mm) muscles were measured at outer and inner gaze fixation, respectively. Bland-Altman plots showed better consistency at outer gaze fixation than at inner gaze fixation for the lateral rectus muscle; the opposite was observed for the medial rectus muscle. More than 80% of the AS-OCT measurements were within 1 mm of the intraoperative measurements at outer gaze fixation for the lateral rectus muscle and inner gaze fixation for the medial rectus muscle.

CONCLUSIONS

Gaze fixation at outer gaze fixation for the lateral rectus muscle and inner gaze fixation for the medial rectus muscle was an appropriate technique to assess limbus and EOM insertion using AS-OCT. [J Pediatr Ophthalmol Strabismus. 2021;58(1):28-33.].

Anterior Segment Optical Coherence Tomography in Locating the Insertion of Horizontal Extraocular Muscles After Strabismus Surgery

PURPOSE

To evaluate the accuracy of anterior segment optical coherence tomography (AS-OCT) for locating horizontal extraocular muscle (EOM) insertion after strabismus surgery.

METHODS

The distance from the limbus to the postoperative muscle insertion was measured with calipers intraoperatively and by AS-OCT during the postoperative visit of adults undergoing strabismus surgery. Images were collected by masked technicians. Intraclass correlation coefficients (ICC) were used to evaluate the agreement between measurements.

RESULTS

Twenty-eight patients were recruited. Measurements were taken from 31 eyes, including 17 lateral and 14 medial rectus muscles. EOM insertion was successfully identified by AS-OCT for 14 (45%) cases. The ICC between intra-operative and AS-OCT measurement was 0.886 when the distance from the limbus to the insertion of EOM was less than 8 mm and 0.001 when the distance from the limbus was between 8 and 10 mm. EOM insertion was undetectable if distance to the limbus was greater than 10 mm.

CONCLUSIONS

AS-OCT can accurately identify post-surgical horizontal muscle insertion if the insertion is less than 8 mm from the limbus. [J Pediatr Ophthalmol Strabismus. 2021;58(1):62-65.].

Evaluation of the insertion distance of the medial rectus in consecutive exotropia by means of intraoperative measure and optical coherence tomography

PURPOSE

To assess the agreement between the intraoperative measurements of the distance from the medial rectus muscles insertion to the limbus and preoperative spectral-domain optical coherence tomography (SD-OCT) in consecutive exotropia (cXT).

METHODS

An analysis was performed on total of 14 medial rectus (MR) muscles of 14 patients who underwent surgery for the treatment of cXT. The limbus-insertion distance of the MR muscles was measured using preoperative SD-OCT and intraoperatively using a calliper. The intraclass correlation coefficient (ICC) and Bland Altman plots were calculated to determine the agreement between the two methods, as well as the correlation.

RESULTS

Mean age was 36.3±16.0 years (range 13-60), with 60% being women. Mean preoperative deviation was 38.7±16.9 prismatic dioptres (PD) (range 16 to 65), being +1.3±6.3 PD (range -12 to +10 PD) after surgery. Intraoperatively the MR insertion was found at 8.7±2.1mm (range 5.5 - 12.0) and by OCT at 7.7±1.2mm (range 5.3 - 10.0). The ICC showed a moderate to good agreement (0.659; 95% confidence interval: 0.157-0.885; P<.001), with a correlation of R=0.792 (P=.011). A better agreement was observed in those MR that were less retro-inserted.

CONCLUSIONS

SD-OCT is able to measure the insertion to the limbus distance of the medial rectus muscles that have been previously operated on, showing moderate to good agreement with intraoperative measurements. However, the agreement was poor in muscles with a large retro-insertion.

Pre-, Intra-, and Post-Operative Evaluation of Extraocular Muscle Insertions Using Optical Coherence Tomography: A Comparison of Four Devices

OCT (optical coherence tomography) is widely used in ophthalmology and pediatric ophthalmology, but limited research has been done on the use of OCT in strabismus. This study investigates the use of different OCT machines to image rectus muscle insertions pre-, intra-, and post-operatively in pediatric strabismus patients. The OCT machines used in the study were a Bioptigen (Leica Microsystems Inc., Buffalo Grove, IL, USA), Spectralis HRA+OCT with Anterior Segment Module (Heidelberg Engineering, Heidelberg, Germany), Visante (Carl Zeiss, Oberkochen, Germany), and Zeiss Rescan 700 (Carl Zeiss, Oberkochen, Germany). Measurements from the machines were compared with the caliper distance measured during the strabismus surgery before disinsertion or after reattachment. The OCT machines had moderate (Bioptigen: 0.62) to good intraclass correlation coefficients (Rescan: 0.83, Spectralis: 0.85, Visante: 0.88) with intra-operative measurements. To our knowledge, this is the first study to use an operating microscope with integrated intra-operative OCT to image rectus muscle insertions. OCT is a useful tool in strabismus surgical patients in the pre-, intra-, and post-operative settings, particularly in patients who have had previous surgery, when the muscle insertion is unknown. The ability to accurately image rectus muscle insertions has significant implications for the management of strabismus patients.

Correlation Between Optical Coherence Tomography and Magnetic Resonance Imaging of Rectus Muscle Thickness Measurements in Graves' Ophthalmopathy

PURPOSE

To assess the correlation between optical coherence tomography (OCT) and magnetic resonance imaging (MRI) measurements of extraocular rectus muscle thickness in patients with Graves' ophthalmopathy.

METHODS

This was a cross-sectional observational study conducted in 62 eyes of 31 patients with Graves' ophthalmopathy. The disease phase was inactive in 20 patients and active in the remaining 11. The OCT measurements obtained were: medial rectus thickness at 7.2 and 9.2 mm from the limbus and lateral rectus thickness at 8.5 mm from the limbus. MRI measurements were maximum transversal diameter (T-MRI), craniocaudal diameter (CC-MRI), and muscle area (A-MRI).

RESULTS

For the whole patient cohort, correlation emerged between the OCT-MR and T-MRI measurements (R = 0.428 to 0.576; P ≤ .002), A-MRI (R = 0.562 to 0.674; P < .001), and CC-MRI (R = 0.286 to 0.293; P ≤ .046). In patients with clinically active Graves' ophthalmopathy, correlations with T-MRI (R = 0.576 to 0.604; P ≤ .010) and A-MRI (R = 0.678 to 0.706; P < .001) were higher. No correlations were detected between OCT and MRI measurements of lateral rectus thickness (P ≥ .177), regardless of disease phase.

CONCLUSIONS

The correlations observed suggest OCT could be a complementary assessment or screening method to detect thickening of the anterior portion of the medial rectus muscle in patients with Graves' ophthalmopathy, which may be especially useful when MRI is not available. [J Pediatr Ophthalmol Strabismus. 2019;56(5):319-326.].

One-Year Outcome Predictors of Strabismus Surgery from Anterior Segment Optical Coherence Tomography with Multiple B-Scan Averaging

Strabismologists are eager to identify preoperative or intraoperative strabismus surgery outcome predictors because of the variable effects in each patient. Conjunctival closure position recession after rectus muscle recession is effective for correcting large angle strabismus. The elasticity of the conjunctiva and Tenon’s capsule is important for strabismus surgery management. In this longitudinal study, we evaluated the prognosis of conjunctiva and Tenon’s capsule thickness (CTT) near the limbus 1 year after strabismus surgery with a limbal conjunctival incision using swept-source anterior segment optical coherence tomography with multiple B-scan averaging. Also, we identified preoperative and/or intraoperative parameters associated with corrective effects 1 year after surgery in 15 consecutive treatment-naïve patients with exotropia or esotropia who underwent recession and resection. The 1-year CTT was greater than the preoperative CTT on the resection side (269 ± 111 vs 183 ± 53 μm, P < 0.001) but was smaller on the recession side (137 ± 54 vs 183 ± 71 μm, P = 0.02). The corrective effect of surgery (1.6 ± 0.3°/mm) was most strongly correlated with preoperative CTT on the recession side (P = 0.005, β = −0.73). Hence, CTT on the recession side may provide adjunctive information for strabismus treatment.

Optical Coherence Tomography Thickness Measurements of the Extraocular Rectus Muscle Tendons in Graves' Ophthalmopathy

PURPOSE

To examine extraocular rectus muscle tendons in patients with Graves' ophthalmopathy using optical coherence tomography (OCT).

METHODS

This was a cross-sectional observational study conducted with 55 healthy controls, 45 patients with clinically inactive Graves' ophthalmopathy, and 12 patients with clinically active Graves' ophthalmopathy. Scanning was performed at the 3- and 9-o'clock positions. The medial rectus tendon thickness was measured at 7.2 and 9.2 mm from the limbus and the lateral rectus tendon thickness was measured at 8.5 and 10.5 mm from the limbus.

RESULTS

The 9.2-mm medial rectus, 8.5-mm lateral rectus, and 10.5-mm lateral rectus tendons were thicker in the inactive Graves' ophthalmopathy group than the control group (240 ± 70, 231 ± 63, and 228 ± 54 µm vs 201 ± 71, 199 ± 53, and 200 ± 32 µm, respectively; P ≤ .011), whereas the 8.5-mm lateral rectus and 9.2-mm medial rectus tendons were thicker in patients with active Graves' ophthalmopathy than patients with inactive Graves' ophthalmopathy (274 ± 77 and 283 ± 68 µm vs 231 ± 63 and 240 ± 70 µm, respectively; P ≤ .048). A correlation was detected between lateral rectus and medial rectus tendon thicknesses and the Graves' ophthalmopathy clinical activity score (R = 0.252, P = .035; and R = 0.291, P = .013, respectively).

CONCLUSIONS

OCT emerged as an accurate method for measuring medial rectus and lateral rectus tendon thicknesses in patients with Graves' ophthalmopathy. The imaging tool was able to detect thicker horizontal rectus tendons in patients with inactive Graves' ophthalmopathy than in controls, and in patients with active compared to inactive disease. [J Pediatr Ophthalmol Strabismus. 2018;55(6):356-362.].

Changes in conjunctival-scleral thickness after strabismus surgery measured with anterior segment optical coherence tomography

PURPOSE

To evaluate changes in conjunctival-scleral thickness following strabismus surgery with anterior segment optical coherence tomography (AS-OCT).

STUDY DESIGN

Prospective, observational, consecutive case series.

METHODS

Distances between the conjunctival epithelium and inner scleral wall were measured with AS-OCT before and 3-5 months after strabismus surgery. The measurements were performed at 1.5 mm (limbus), 7.0 mm (insertion), and 8.0 mm (tendon) posterior to the scleral spur on the lateral rectus muscle (LR); and 1.5 mm (limbus), 4.0 mm (insertion), and 5.5 mm (tendon) posterior to the scleral spur on the medial rectus muscle (MR). Thirty-three extraocular muscles (20 LRs and 13 MRs) from 23 subjects were studied.

RESULTS

Thicknesses were significantly less at the insertion (0.95-0.78 mm; p < 0.001) and tendon (0.99-0.78 mm; p < 0.001) after LR recession and at the tendon (1.21-0.92 mm; p = 0.02) after MR recession. Thicknesses were significantly greater at the insertion (0.82-1.07 mm; p = 0.01) and tendon (0.95-1.28 mm; p = 0.01) after MR resection or plication and at the limbus, insertion, and tendon (0.75-0.90 mm, 0.94-1.19 mm, 1.03-1.28 mm, respectively; all p = 0.04) after LR resection or plication.

CONCLUSION

Conjunctival-scleral thicknesses showed various changes after recession and resection or plication. These findings may help detect previous surgical operations when conjunctival scarring and ciliary vessel changes are unclear.

Assessment of extraocular muscle thickness and correlation study using optical coherence tomography

OBJECTIVE

To report reference values for the horizontal rectus muscles thickness using Spectral Domain optical coherence tomography (SD-OCT), and to evaluate whether there are any correlations between the muscle thickness and gender, age, or axial length (AL).

MATERIAL AND METHODS

A cross-sectional study was conducted on 131 right eyes of healthy subjects. The gender and age were recorded, and axial length was measured using an optical biometer. The medial rectus (MR) muscle thickness was measured at 7.2 and 9.2mm from the limbus, and the lateral rectus (LR) at 8.5 and 10.5mm from the limbus using OCT. A multivariate model was adjusted to determine whether gender, age, and axial length could have an impact on the muscle thickness.

RESULTS

Mean age was 43.3±20.9 years (range 6-86), and 59% were women. Mean AL was 24.9±2.7mm (range: 20.4-33.8). Mean thickness was 188.5±51.2μm (range 69-342) for the LR at 8.5 and 186.5±45.9μm (range 75-269) at 10.5mm, and for the MR, 158.1±39.1μm (range 69-273) at 7.2mm and 193.7±55.9μm (range 105-386) at 9.2mm. A correlation was observed between the AL and MR thickness (R=-.255; P=.023) while no correlation was observed for the LR (P≥0.203). No correlations were found between thickness and gender or thickness and age (P≥0.125).

CONCLUSIONS

The reference ranges of the horizontal rectus muscles thickness was described using SD-OCT, observing an association between the AL and the MR thickness.

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.

Agreement Between Three Optical Coherence Tomography Devices to Assess the Insertion Distance and Thickness of Horizontal Rectus Muscles

PURPOSE

To assess the agreement between two different spectral domain (SD-OCT) and one swept source (SS-OCT) optical coherence tomography device to measure the insertion distance and the thickness of the horizontal rectus muscles.

METHODS

Seventy eyes from 35 healthy patients were studied. Three OCT instruments-Spectralis (Heidelberg Engineering Inc., Heidelberg, Germany), Cirrus 5000 (Carl Zeiss Meditec, Dublin, CA), and Triton (Topcon, Inc., Tokyo, Japan)-were used to measure the limbus insertion distance and the thickness of the lateral rectus and medial rectus muscles. The intraclass correlation coefficient (ICC) was calculated to determine the reproducibility and the agreement between the three methods.

RESULTS

Measurement of the limbus insertion distance was possible in 100% of cases with the three OCT devices. The thickness could be measured in 75% or more patients with Spectralis, 74% or more with Cirrus, and 78% or more with Triton. The agreement of the insertion distance measurements between the three devices ranged from an ICC of 0.629 or greater to 0.887; for the muscle thickness, the ICC ranged from 0.495 or greater to 0.854. The best agreement existed between the Spectralis and Topcon devices for insertion distance (ICC = 0.715 to 0.887) and for muscle thickness (ICC = 0.641 to 0.854). The reproducibility of each device was good and was higher for insertion distance (ICC = 0.880) than for muscle thickness (ICC = 0.736). The highest reproducibility values were obtained with Triton.

CONCLUSIONS

The three OCT devices permitted accurate and reproducible measurements of the limbus insertion distance and the thickness of the horizontal rectus muscles, showing moderate to good agreement between the SS-OCT and the two SD-OCT instruments. [J Pediatr Ophthalmol Strabismus. 2017;54(3):168-176.].

Agreement between intraoperative measurements and optical coherence tomography of the limbus-insertion distance of the extraocular muscles

OBJECTIVE

To assess the agreement between intraoperative measurements of the limbus-insertion distance of the extraocular muscles with those measured by spectral domain optical coherence tomography.

METHODS

An analysis was made of a total of 67 muscles of 21 patients with strabismus. The limbus-insertion distance of the horizontal rectus muscles were measured using pre-operative SD-OCT and intra-operatively in 2 ways: 1) direct, after a conjunctival dissection in patients who underwent surgery, or 2) transconjunctival in patients who were treated with botulinum toxin, or in those who were not going to be operated. The intraclass correlation coefficient and Bland-Altman plots were calculated to determine the concordance between the 2 methods.

RESULTS

The mean age was 45.9 ±20.9 years (range 16 to 85), with 52% being women. The percentage of identification by direct intraoperative measurement was 95.6% (22/23), by transconjunctival intraoperative measurement 90.9% (40/44), and by OCT 85% (57/67), with 22 muscles finally being analysed for the agreement study between direct intraoperative measurement and OCT measurements, and 35 muscles for the agreement between transconjuctival intraoperative measurement and OCT. The intraclass correlation coefficient showed good agreement with OCT and direct intraoperative measurements (0.931; 95% confidence interval (95% CI): 0.839-0.972; P<.001), and with transconjunctival intraoperative measurements (0.889; 95% CI: 0.790-0.942; P<.001).

CONCLUSIONS

The SD-OCT is an effective technique to measure the distance from the insertion of the horizontal rectus muscles to the limbus, with a high agreement with intraoperative measurements being demonstrated.

Spectral domain optical coherence tomography to assess the insertion of extraocular rectus muscles

PURPOSE

To determine the distance of the horizontal rectus muscle insertion to the limbus using spectral domain optical coherence tomography (SD-OCT) and to evaluate whether results are correlated with sex, age, or axial length.

METHODS

The right eyes of healthy, white subjects were imaged with SD-OCT. Subjects' sex and age were recorded, and axial length was measured using an optical biometer. The distance from the horizontal rectus insertion to the limbus was measured. The intraclass correlation coefficient (ICC) was used to assess the reproducibility of the measurements with a subset of images. A multivariate model was adjusted to analyze whether sex, age, and axial length was correlated with insertion distance.

RESULTS

A total of 187 right eyes were included. Mean participant age was 43.7 ± 22.1 years (range, 6-85). Of the 187 patients, 129 were female; 25 were children. Mean axial length was 23.9 ± 1.6 mm (range, 20.4-29.3). Mean rectus insertion distance to the limbus was 6.47 ± 0.52 mm (range, 5.2-7.6 mm) for the lateral rectus muscle and 5.22 ± 0.51 mm (range, 4.1-6.1 mm) for the medial rectus muscle. ICC was >0.87 for intra- and interobserver reproducibility. The insertion-limbus distance was correlated with sex, being greater in males (P = 0.040 for the lateral rectus muscle; P = 0.036 for medial rectus muscle). There was no correlation between this distance and axial length or age (P > 0.156).

CONCLUSIONS

In this study cohort, the insertion distance of the horizontal rectus muscles to the limbus on SD-OCT was greater in males than females; however, age and axial length were not correlated with insertion distance.

Anterior Segment Optical Coherence Tomography of the Horizontal and Vertical Extraocular Muscles With Measurement of the Insertion to Limbus Distance

PURPOSE

To assess the possibility of determining the insertion distance from the limbus of horizontal and vertical extraocular rectus muscles with anterior segment optical coherence tomography (AS-OCT).

METHODS

The right eyes of 46 patients underwent AS-OCT. The horizontal and vertical extraocular rectus muscle insertion distances from the limbus were measured in a masked fashion by two pediatric ophthalmologists.

RESULTS

Forty-two lateral rectus, 43 medial rectus, 35 inferior rectus, and 40 superior rectus muscles of the right eyes of 46 patients were included. Insertion to limbus measurements (mean ± SD) were as follows: lateral rectus = mean 6.8 ± 0.7 mm, range = 4.8 to 8.4 mm; medial rectus = mean 5.7 ± 0.8 mm, range = 4.3 to 7.8 mm; inferior rectus = mean 6.0 ± 0.6 mm, range = 4.8 to 7.0 mm; superior rectus = mean 6.8 ± 0.6 mm, range = 5.5 to 8.1 mm. The intraobserver and interobserver correlation coefficients for the insertion to limbus measurements of all four rectus muscles exceeded 0.75 (excellent correlation).

CONCLUSIONS

The study showed that AS-OCT is capable of imaging all four of the rectus muscle insertions and measuring the insertion to limbus distance, and is the second AS-OCT study to image the superior and inferior rectus muscle insertions. The insertion to limbus measurements between examiners and on repeat measurements were consistent and reproducible. The ability to accurately image extraocular rectus muscle insertions may have future implications for the preoperative procedure planning in patients who have had previous surgery. [J Pediatr Ophthalmol Strabismus. 2016;53(3):141-145.].