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

The measurement and correlation analysis of scleral and choroid thickness in branch retinal vein occlusion

To use Optical Coherence Tomography (OCT) to measure scleral thickness (ST) and subfoveal choroid thickness (SFCT) in patients with Branch Retinal Vein Occlusion (BRVO) and to conduct a correlation analysis. A cross-sectional study was conducted. From May 2022 to December 2022, a total of 34 cases (68 eyes) of untreated unilateral Branch Retinal Vein Occlusion (BRVO) patients were recruited at the Affiliated Eye Hospital of Nanchang University. Among these cases, 31 were temporal branch vein occlusions, 2 were nasal branch occlusions, and 1 was a superior branch occlusion. Additionally, 39 cases (39 eyes) of gender- and age-matched control eyes were included in the study. Anterior Segment Optical Coherence Tomography (AS-OCT) was used to measure ST at 6 mm superior, inferior, nasal, and temporal to the limbus, while Enhanced Depth Imaging Optical Coherence Tomography (EDI-OCT) was used to measure SFCT. The differences in ST and SFCT between the affected eye, contralateral eye, and control eye of BRVO patients were compared and analyzed for correlation. The axial lengths of the BRVO-affected eye, contralateral eye, and control group were (22.92 ± 0.30) mm, (22.89 ± 0.32) mm and (22.90 ± 0.28) mm respectively, with no significant difference in axial length between the affected eye and contralateral eye (P > 0.05). The SFCT and ST measurements in different areas showed significant differences between the BRVO-affected eye, contralateral eye in BRVO patients (P < 0.05). The CRT of BRVO-affected eyes was significantly higher than that of the contralateral eyes and the control eyes (P < 0.001). In comparison between BRVO-affected eyes and control eyes, there were no statistically significant differences in age and axial length between the two groups (P > 0.05). However, significant differences were observed in SFCT and temporal, nasal, superior, and inferior ST between the two groups (P < 0.05). The difference in temporal ST between the contralateral eyes and the control eyes was not statistically significant (t = - 0.35, P = 0.73). However, the contralateral group showed statistically significant increases in SFCT, nasal, superior and inferior ST compared to control eyes (t = - 3.153, 3.27, 4.21, 4.79, P = 0.002, 0.002, < 0.001, < 0.001). However, the difference between the CRT of the contralateral and control eyes was not statistically significant (P = 0.421). When comparing SFCT and ST between BRVO-affected eyes with and without macular edema, no statistically significant differences were found (t = - 1.10, 0.45, - 1.30, - 0.30, 1.00; P = 0.28, 0.66, 0.21, 0.77, 0.33). The thickness of SFCT and temporal ST in major BRVO group is higher than the macular BRVO group and the difference was statistically significant (t = 6.39, 7.17, P < 0.001 for all). Pearson correlation analysis revealed that in BRVO patients, there was a significant positive correlation between SFCT/CRT and temporal ST (r = 0.288, 0.355, P = 0.049, 0.04). However, there was no correlation between SFCT/CRT and nasal ST, superior ST, and inferior ST (P > 0.05). In BRVO patients, both SFCT/CRT and ST increase, and there is a significant correlation between SFCT/CRT and the ST at the site of vascular occlusion.

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.

Medial Rectus Muscle Resection Versus Plication: A Comparison of Conjunctival-Scleral Thickness Measured by AS-OCT

PURPOSE

To compare conjunctival-scleral thickness measured with anterior segment optical coherence tomography before and after medial rectus muscle resection and plication for exotropia.

METHODS

In this prospective observational study, patients with exotropia aged 5 years and older who underwent medial rectus muscle resection or plication through limbal incision of the conjunctiva between April 2016 and June 2018 were enrolled. Conjunctivalscleral thickness was measured with anterior segment optical coherence tomography before and 3 and 6 months after surgery at 1.5 mm (limbus), 4 mm (insertion), and 5.5 mm (tendon) posterior to the scleral spur. One examiner made measurements twice blinded for the initial data. Conjunctival-scleral thickness was compared between groups using the Mann-Whitney U test.

RESULTS

Twenty participants were divided into two groups: resection (n = 11) and plication (n = 9). The respective conjunctival-scleral thicknesses before and 3 and 6 months after surgery in the resection group were as follows: 0.76, 0.90, and 0.86 mm at the limbus; 0.86, 1.18, and 1.12 mm at the insertion; and 1.04, 1.41, and 1.33 mm at the tendon. Corresponding values in the plication group were as follows: 0.74, 0.87, and 0.81 mm at the limbus; 0.84, 1.16, and 1.08 mm at the insertion; and 1.00, 1.39, and 1.27 mm at the tendon. No between-group differences were observed at any location or time.

CONCLUSIONS

No differences in conjunctival-scleral thickness were observed between the resection and plication groups before surgery or at 3 months and 6 months postoperatively. [J Pediatr Ophthalmol Strabismus. 2022;59(4):274-278.].

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.].

Shape analysis of rectus extraocular muscles with age and axial length using anterior segment optical coherence tomography

Purpose

This study aimed to evaluate the shape of the extraocular muscles (EOMs) in normal subjects using the en-face images of anterior segment optical coherence tomography (AS-OCT). The EOM insertion and the direction of the muscle fibers were investigated.

Subjects and methods

A total of 97 healthy normal subjects (194 eyes) at Okayama University Hospital (age, 47.1±21.5 years; range, 8–79 years) participated in the study. A series of 256 tomographic images of the rectus EOMs were captured using the C-scan function of the AS-OCT (CASIA2, TOMEY Co., Japan), and the images were converted to en-face images in multi-TIFF format. The anterior chamber angle to EOM insertion distance (AID) and the angle of the muscle fibers from the insertion site (angle of muscles) were measured from the images. The correlations of AID and angle of muscles with age and axial length were investigated and evaluated.

Results

AID and angle of muscles were significantly correlated with age or axial length in some EOMs. The AIDs of medial rectus (MR) (P = 0.000) and superior rectus (SR) (P = 0.005) shortened with age. The AIDs of MR (P = 0.001) and inferior rectus (IR) (P = 0.035) elongated with axial length, whereas lateral rectus (LR) (P = 0.013) shortened. The angles of MR (P = 0.001) and LR (P = 0.000) were found to have a more downward direction toward the posterior in older subjects.

Conclusion

En-face images can be created by AS-OCT, and the shape of the EOMs in normal subjects using these image measurements was available. With the ability to assess the EOMs, AID and angle of muscles are expected give useful information for treating and diagnosing strabismus-related diseases.

Interocular difference associated with myopic progression following unilateral lateral rectus recession in early school-aged children

PURPOSE

To compare refractive changes in operated eyes and fellow unoperated eyes following unilateral lateral rectus recession in early school-aged children.

STUDY DESIGN

A retrospective case control study.

METHODS

The medical records of children under ten years of age with intermittent exotropia who underwent unilateral lateral recession surgery were reviewed. The operated eyes were reviewed and the fellow unoperated eyes were used as control. The rate of myopic progression was calculated by spherical equivalent (SE) changes per year, and by the rate of refractive growth (RRG) equation.

RESULTS

SE showed a myopic shift one week after surgery and in the following months, from -1.43 ± 1.84 diopters (D) at 1 week post operation to -1.57 ± 2.22 D at one year and, finally -2.95 ± 2.97 D at the average 4.62 years following surgery. However, the SE shift was not significantly different from the unoperated eye. The low myopia group (under -3.0 D) showed a significantly higher myopic change in the operated eye until one year post operation (p = 0.022). The average myopic shift ratio was -0.53 ± 0.46 D yearly in the operated eye.

CONCLUSIONS

This study presents data of a large series of refractive changes secondary to lateral rectus recession, and of long-term myopia progression in Korean population.

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.