Shorter scleral spur in eyes with primary open-angle glaucoma

The anterior scleral thickness in primary open-angle glaucoma with high myopia

Purpose

This study aimed to investigate and compare the anterior scleral thickness (AST) among high myopia (HM), primary open-angle glaucoma (POAG), and POAG with HM (HMPOAG) groups.

Methods

Thirty-two HM eyes, 30 POAG eyes, and 31 HMPOAG eyes were included. The Schlemm's canal (SC) area, trabecular meshwork (TM) thickness, scleral spur (SS) length, and AST were measured using swept-source optical coherence tomography. AST was measured at 0 mm (AST0), 1 mm (AST1), 2 mm (AST2), and 3 mm (AST3) from SS.

Results

The HMPOAG group had significantly thinner AST, SS length, and TM thickness than the HM and POAG groups (all p < 0.05). In addition, the SC area of the HMPOAG group was also significantly smaller than that of the HM group (p < 0.001).

Conclusion

The HMPOAG group had the thinnest AST, shortest SS, thinnest TM, and smallest SC. The thinnest AST might contribute to the shortest SS, and further to the thinnest TM and smallest SC in the HMPOAG group. AST might be a novel clinical indicator in the prediction and evaluation of POAG.

Unveiling Novel Structural Biomarkers for the Diagnosis of Glaucoma

Glaucoma, a leading cause of irreversible blindness, poses a significant global health burden. Early detection is crucial for effective management and prevention of vision loss. This study presents a collection of novel structural biomarkers in glaucoma diagnosis. By employing advanced imaging techniques and data analysis algorithms, we now can recognize indicators of glaucomatous progression. Many research studies have revealed a correlation between the structural changes in the eye or brain, particularly in the optic nerve head and retinal nerve fiber layer, and the progression of glaucoma. These biomarkers demonstrate value in distinguishing glaucomatous eyes from healthy ones, even in the early stages of the disease. By facilitating timely detection and monitoring, they hold the potential to mitigate vision impairment and improve patient outcomes. This study marks an advancement in the field of glaucoma, offering a promising avenue for enhancing the diagnosis and possible management.

Position of the ISTENT Inject® Trabecular Micro-Bypass System Visualized with the NIDEK GS-1 Gonioscope-A Postoperative Analysis

Glaucoma is one of the leading causes of irreversible blindness globally and is characterized by the gradual loss of retinal ganglion cells. The primary risk factor for the development and progression of glaucoma is increased intraocular pressure (IOP). Numerous surgical interventions exist to lower IOP should conservative therapy fail. One trend in recent years has been minimally invasive glaucoma surgery (MIGS) as an alternative to traditional methods. The ISTENT inject® is an ab interno trabecular micro-bypass implant designed to be implanted through the trabecular meshwork into the Schlemm's canal to lower IOP. The aim of the study was the postoperative visualization and description of the positioning of the ISTENT inject® using automated circumferential goniophotography. Patients with symptomatic cataracts and mild to moderate primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PEX), and pigment-dispersion glaucoma were included who underwent combined cataract surgery with the ISTENT inject® and received postoperative automated gonioscopy with the NIDEK Gonioscope GS-1 to visualize the location of the implant. Twenty-four implants of 14 eyes in 11 patients could be visualized. Out of the implants, 14.3% were in the trabecular meshwork, 46.4% were at the border between the trabecular meshwork and scleral spur, 25% were below the trabecular meshwork, and 14.3% of the implants were not detectable in the gonioscopy. In the overall cohort, a statistically significant IOP reduction was found over the 12-month postoperative observation period. Even in three eyes, in each of which both stents were located below the trabecular meshwork, an IOP reduction over 12 months was observed compared to the baseline IOP. In this study, vertical two-dimensional positioning of the ISTENT inject® was performed for the first time using NIDKE GS-1 automated 360° goniophotography. The method is suitable for postoperative visualization, control, and documentation of positioning after ISTENT inject® implantation. Further studies are needed to analyze the correlation between positioning of the ISTENT inject® in the chamber angle and postoperative IOP reduction.

PreserFlo™ MicroShunt Versus Ab Externo Canaloplasty in Patients With Moderate to Advanced Open-Angle Glaucoma: 12-Month Follow-Up of a Single-Center Retrospective Study

Purpose To evaluate and compare the efficacy and safety of the PreserFlo MicoShunt and the canaloplasty in patients with moderate to advanced glaucoma. Methods In this retrospective study, 300 patients with moderate to advanced glaucoma underwent either the implantation of the PreserFlo™ MicroShunt (group A) or a canaloplasty (group B). All patients underwent regular follow-up examinations in our department every two days, every two weeks, and every three, six, and 12 months postoperatively. Examinations included measurement of the best corrected visual acuity (BCVA), slit-lamp biomicroscopy of the anterior and posterior segments, intraocular pressure (IOP) measurement using Goldmann applanation tonometry, visual field perimetry, and measurement of the endothelial cell density (ECD). Efficacy was shown by the absolute and qualified success rates calculated with the Kaplan-Meyer analysis. Results  In group A, IOP was significantly reduced at 12 months (13.37 ± 3.94 mmHg, p≤ 0.01) postoperatively in comparison to baseline (23.47 ± 8.39 mmHg). In group B, there was also a reduction in IOP at 12 months (14.32 ± 3.59 mmHg, p≤ 0.01) in comparison to the baseline (18.86 ± 5.82 mmHg). Comparing both groups, the IOP of patients who received the PreserFlo™ MicroShunt was significantly lower than the IOP of patients receiving canaloplasty after 12 months (p=0.049). Patients in both groups were treated with significantly fewer topical agents after 12 months (group A: baseline = 2.53±1.56; 12 months: 0.43 ± 0.83, p≤0.01; group B: baseline 2.62 ± 0.87; 12 months: 1.52 ± 0.99, p≤0.01). Patients receiving the PreserFlo™ MicroShunt applied significantly fewer topical agents than patients who underwent canaloplasty (p≤ 0.01). One year after surgery, the cumulative probability of absolute success was 81.33% in group A and 14.67% in group B. After one year, the cumulative probability of qualified success was 93.33% in group A and 82.00% in group B. Conclusion The PreserFlo™ as well as the canaloplasty offer many advantages and only a few disadvantages for patients with glaucoma. However, the respective patient's history and individual risk profile play an important role in the decision of the glaucoma specialist regarding the most appropriate surgical treatment for each patient. Patients with a high risk of conjunctival scarring and postoperative complications may benefit more from a canaloplasty, whereas patients who need a lower average IOP and show intolerance to any topical agents may require the PreserFlo™ implantation.

The Anterior Segment Biometrics in High Myopia Eyes

INTRODUCTION

The aim of this study was to investigate and compare the anterior segment biometrics in high myopia and control groups.

METHODS

Thirty-four eyes of 34 high myopia patients and 42 eyes of 42 control subjects were included. Schlemm's canal (SC) area, trabecular meshwork (TM) thickness and length, scleral spur (SS) length, and anterior scleral thickness (AST) were measured using swept-source optical coherence tomography. Associations between SC area, TM thickness, TM length, SS length, and AST were also estimated.

RESULTS

SC area, TM thickness, and SS length were significantly associated with AST0 (AST at 0 mm from SS) in both high myopia and control groups. AST0 (702.61 ± 78.05 vs. 729.12 ± 95.87 μm, p = 0.085) and SS length (206.25 ± 52.25 vs. 212.09 ± 51.86 μm, p = 0.556) were not significantly different between high myopia and control groups, whereas SC area (6,622.68 ± 1,130.06 vs. 6,105.85 ± 1,297.84 μm2, p = 0.015) was significantly greater and TM thickness (96.15 ± 34.40 vs. 107.93 ± 29.97 μm, p = 0.048) was significantly thinner in high myopia group than in control group.

CONCLUSION

SC area and TM thickness were significantly associated with AST0, while AST0 and SS length were not significantly different between high myopia and control groups. The changes in SC and TM dimensions in high myopia eyes might be caused by factors other than AST0 and SS length.

The anterior scleral thickness in eyes with primary open-angle glaucoma

Purpose

To investigate the anterior scleral thickness (AST) and its associations with Schlemm’s canal (SC) area, trabecular meshwork (TM) thickness and length, and scleral spur (SS) length in healthy and primary open-angle glaucoma (POAG) groups.

Methods

Thirty-five eyes of 35 healthy subjects and 23 eyes of 23 patients with POAG were included. The AST, SC area, TM thickness and length, and SS length were measured using swept-source optical coherence tomography. AST was measured at 0 mm (AST0), 1 mm (AST1), 2 mm (AST2), and 3 mm (AST3) from SS. Associations between AST and SC area, TM thickness and length, and SS length were also estimated.

Results

AST0 (728.84 ± 99.33 vs. 657.39 ± 67.02 μm, p < 0.001), AST1 (537.79 ± 79.55 vs. 506.83 ± 57.37 μm, p = 0.038), AST3 (571.09 ± 79.15 vs. 532.13 ± 59.84 μm, p = 0.009), SC area (6304.26 ± 1238.72 vs. 4755.64 ± 1122.71 μm2, p < 0.001), TM thickness (107.21 ± 31.26 vs. 94.51 ± 24.18 μm, p = 0.035), TM length (736.20 ± 141.85 vs. 656.43 ± 127.03 μm, p = 0.004), and SS length (219.89 ± 50.29 vs. 174.54 ± 35.58 μm, p < 0.001) were significantly greater in healthy group than in POAG group. In addition, SC area, TM thickness, and SS length were significantly and positively associated with AST0 in the healthy group, whereas no similar associations were observed in the POAG group.

Conclusions

Compared with the healthy group, AST was significantly thinner in the POAG group, which also had smaller SC and TM dimensions. Moreover, the SC area, TM thickness, and SS length were significantly and positively associated with AST in the healthy group. Thus, AST might play an important role in maintaining TM and SC morphology and further in the pathogenesis of POAG.

Reduction in trabecular meshwork stem cell content in donor eyes with primary open angle glaucoma

We previously identified and characterized human trabecular meshwork stem cells (TMSCs) based on high expression of ABCG2/p75 positivity and high nucleus to cytoplasmic ratio. These TMSCs expressing high ABCG2 and p75 were located to the insert region of the human TM. Additionally, we demonstrated an age-related reduction in the TMSC content which was significantly associated with TM cell loss. In continuation, this study was aimed to determine the TMSC content in glaucomatous donor eyes wherein a drastic reduction in TM cellularity has already been reported. Anterior segments from known glaucomatous (n = 6) and age-matched normal (n = 8) donors were dissected into four quadrants. A minimum of three sections from each quadrant were used for histopathological analysis as well as immunostaining. Analysis of hematoxylin and eosin-stained sections from glaucomatous tissues revealed a decrease in total TM cellularity, thickening of trabecular beams, fusion of trabeculae, absence of patent Schlemm's canal compared to age-matched controls. In addition, the TM thickness at various positions of the meshwork and the coronal as well as the meridional diameters of the Schlemm's canal were observed to be significantly reduced in glaucomatous eyes. Further, sections from both the groups were immunostained for universal stem cell marker ABCG2 and neural crest derived stem cell marker p75. The images were acquired using Leica SP8 confocal microscope. Quantification of total TM cellularity based on nuclear counterstain (mean ± SD) using ImageJ identified 69.33 ± 12.77 cells/section in control eyes. In glaucomatous donors, the TM cellularity was found to be reduced significantly to 41.83 ± 9.0 (p = 0.0007). In addition, a reduction in the percentage of TMSCs (cells with high ABCG2 expression and p75 positivity) was evident in glaucomatous donors (0.14 ± 0.17%) compared to age-matched controls (4.73 ± 5.46%) (p = 0.064). Thus, the present study confirmed the significant decline in TM cellularity and a reducing trend in the TMSC content, though this reduction was non-significant in glaucomatous donor eyes. Further studies are essential to elucidate the role of TMSCs in the pathogenesis of primary open angle glaucoma.

Dynamic changes of scleral spur length in different accommodation stimuli states

This study aimed to evaluate the scleral spur length (SSL) in response to different accommodation stimuli states, as well as the correlation with Schlemm’s canal (SC) and trabecular meshwork (TM). 74 children were recruited for this study. The 0D, − 4D, and − 8.0 D accommodation stimuli state was achieved by looking at a variable distance optotype. The ciliary muscle (CM), scleral spur (SS), SC, and TM were imaged by swept-source optical coherence tomography. The SSL (Method III) increased significantly from 221.56 ± 30.74 μm at base state to 234.99 ± 30.11 μm at − 4D accommodation stimuli state (p = 0.028) and increased to 250.09 ± 29.87 μm at − 8D accommodation stimuli state (p = 0.011). Method III had the largest areas under receiver operating characteristic (ROC) curves (0.798, 95% CI 0.721–0.875). Moreover, CM 1, SC, and trabecular meshwork length (TML) were significantly correlated with SSL (Method III) (p < 0.05). These findings suggest that the contractile ability and compliance of the SS play an important role in maintaining the morphology of the SC. Moreover, the force of accommodation regulates the SC size by increasing the length of SS.

Level-Set Method for Image Analysis of Schlemm's Canal and Trabecular Meshwork

Purpose

To evaluate different segmentation methods in analyzing Schlemm's canal (SC) and the trabecular meshwork (TM) in ultrasound biomicroscopy (UBM) images.

Methods

Twenty-six healthy volunteers were recruited. The intraocular pressure (IOP) was measured while study subjects blew a trumpet. Images were obtained at different IOPs by 50-MHz UBM. ImageJ software and three segmentation methods—K-means, fuzzy C-means, and level set—were applied to segment the UBM images. The quantitative analysis of the TM-SC region was based on the segmentation results. The relative error and the interclass correlation coefficient (ICC) were used to quantify the accuracy and the repeatability of measurements. Pearson correlation analysis was conducted to evaluate the associations between the IOP and the TM and SC geometric measurements.

Results

A total of 104 UBM images were obtained. Among them, 84 were adequately clear to be segmented. The level-set method results had a higher similarity to ImageJ results than the other two methods. The ICC values of the level-set method were 0.97, 0.95, 0.9, and 0.57, respectively. Pearson correlation coefficients for the IOP to the SC area, SC perimeter, SC length, and TM width were −0.91, −0.72, −0.66, and −0.61 (P < 0.0001), respectively.

Conclusions

The level-set method showed better accuracy than the other two methods. Compared with manual methods, it can achieve similar precision, better repeatability, and greater efficiency. Therefore, the level-set method can be used for reliable UBM image segmentation.

Translational Relevance

The level-set method can be used to analyze TM and SC region in UBM images semiautomatically.

Comparison of measurements of anterior chamber angle via anterior segment optical coherence tomography and ultrasound biomicroscopy

BACKGROUND

Glaucoma is an irreversible optic neuropathy with the loss of visual field and decrease of vision. The variable clinical manifestations may result in differential diagnostic difficulties. The early screening and diagnosis of glaucoma are currently experiencing a demand for anterior segment analysis tools that can gather more information with one short measurement. Therefore, we analyzed the agreement, difference, and correlation of chamber angle parameters such as angel opening distance at 500 μm (AOD500) and trabeculo-iris space area at 500 μm² (TISA500) measured by anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM).

AIM

To compare the differences, correlation, and agreement in measuring AOD500 and TISA500 by AS-OCT and UBM.

METHODS

Both AS-OCT and UBM were performed to measure AOD500 and TISA500 in 45 subjects (72 eyes). All subjects without glaucoma were collected from October 2015 to August 2016 at the Ophthalmology Department of the Fourth Affiliated Hospital of China Medical University. Data of the two groups (AOD500 and TISA500) were compared by nonparametric tests. Pearson correlative analysis and Bland–Altman analysis were used to compare the correlation and agreement.

RESULTS

There were no significant differences between AS-OCT and UBM in measuring AOD500 (P1 = 0.110, P2 = 0.633, P3 = 0.078, and P4 = 0.474) and TISA500 (P1 = 0.584, P2 = 0.889, P3 = 0.297, and P4 = 0.550) of the four quadrants of the anterior chamber angle. There was a high correlation in measuring AOD500 (r1 = 0.562, r2 = 0.671, r3 = 0.635, and r4 = 0.720; P < 0.001) and TISA500 (r1 = 0.584, r2 = 0.889, r3 = 0.297, and r4 = 0.550; P < 0.001). There was a good agreement in measuring AOD500 and TISA500 by the two modalities.

CONCLUSION

There is a high correlation and agreement between AOD500 and TISA500 measurements by AS-OCT and UBM. They are interchangeable under some circumstances. AS-OCT proves to be a better early screening tool for glaucoma.

Intelligent-assistant system for scleral spur location

A system based on the use of two artificial neural networks (ANNs) to determine the location of the scleral spur of the human eye in ocular images generated by an ultrasound biomicroscopy is presented in this paper. The two ANNs establish a relationship between the distance of four manually placed landmarks in an ocular image with the coordinates of the scleral spur. The latter coordinates are generated by the expert knowledge of a subject matter specialist. Trained ANNs that generate good results for scleral spur location are incorporated into a software system. Statistical indicators and results yield an efficiency performance above 95%.

Diagnostic power of scleral spur length in primary open-angle glaucoma

Purpose

To investigate the diagnostic capability of scleral spur length in discriminating eyes with primary open-angle glaucoma (POAG) from healthy eyes.

Methods

Seventy-eight eyes of 78 patients with POAG and 93 eyes of 93 age-, sex- and axial length-matched healthy subjects were included. The scleral spur length was measured using swept-source optical coherence tomography. Receiver operating characteristic (ROC) curves were derived based on the measurements.

Results

The scleral spur length was significantly shorter in POAG eyes compared with healthy eyes (Method I, 164.91 ± 23.36 vs. 197.60 ± 25.32 μm; Method II, 145.15 ± 16.59 vs. 166.95 ± 19.31 μm; Method III, 162.33 ± 22.83 vs. 185.12 ± 23.58 μm, respectively; all p < 0.001). The areas under ROC curves were 0.841 (Method I), 0.810 (Method II), and 0.753 (Method III) for the scleral spur length. Moreover, Schlemm’s canal area was significantly associated with the scleral spur length (Method I) in both POAG (β = 0.027; p < 0.001) and healthy (β = 0.016; p = 0.009) groups.

Conclusions

The scleral spur length had a good discriminating capability between POAG and healthy eyes, and it could be a novel biomarker for POAG evaluation clinically.

Disease-related and age-related changes of anterior chamber angle structures in patients with primary congenital glaucoma: An in vivo high-frequency ultrasound biomicroscopy-based study

OBJECTIVES

To provide in vivo measurements of anterior chamber angle structures and their relationship with age as evaluated by high-frequency ultrasound biomicroscopy (UBM) in patients with primary congenital glaucoma (PCG).

METHODS

High-frequency UBM was done for 51 PCG eyes from 40 patients (aged from 3 to 96 months) and 11 unaffected contralateral eyes. Parameters, including the proportion of observable abnormal tissue membrane and Schlemm's canal, the largest cross-sectional area (CSA) of Schlemm's canal (SC), SC meridional diameter, trabecular-iris angle (TIA), trabecular meshwork (TM) thickness, iris thickness, ciliary process length, and corneal limbus thickness were compared between the two groups and their relationship with age was explored in PCG eyes.

RESULTS

Abnormal tissue membrane was detected in 27.5% of PCG eyes and none in unaffected eyes. SC was observed in 73.1% of PGC eyes compared to 100% in unaffected eyes (P<0.001). The largest CSA of SC, SC meridional diameter, iris thickness, and corneal limbus thickness were all significantly smaller in PCG eyes compared to unaffected eyes (all P<0.05). TIA and ciliary process length in unaffected eyes were smaller than PCG eyes (both P<0.05). The largest CSA of SC, TM thickness, iris thickness, and ciliary process length were all significantly correlated to age in PCG eyes (P<0.05).

CONCLUSIONS

The anatomical information evaluated by high-frequency UBM may provide glaucoma specialists a useful tool to aid in understanding the dysgenesis and changes with age of anterior chamber angle in PCG.

Progression on canaloplasty for primary open angle glaucoma

As a non-penetrating glaucoma surgery (NPGS), canaloplasty aims to reconstruct the physiological outflow of aqueous humor by dilating the Schlemm's canal. Ab interno canaloplasty (ABiC), which can reconstruct the natural outflow pathways of aqueous humor in mild-to-moderate primary open angle glaucoma (POAG) patients, is a new minimally invasive glaucoma surgery (MIGS) procedure improving from traditional canaloplasty. Canaloplasty can reduce intraocular pressure (IOP) with high efficiency and security. There are no complications such as scar formation and encapsulation for this no-bleb canaloplasty.

Comparison of the trabecular meshwork length between open and closed angle with evaluation of the scleral spur location

This study analysed the trabecular meshwork (TM) length in open and closed angle patients and presented a better method for locating the scleral spur using Schwalbe’s line method in anterior segment optical coherence tomography (AS-OCT). Patients who underwent AS-OCT at Yonsei University Gangnam Severance Hospital we enrolled; 58 and 57 open and closed angle eyes, respectively. We measured the distance from the scleral spur to Schwalbe’s line as the TM length and compared it between open and closed angle patients, and to previous studies. TM length was applied to locate the scleral spur using Schwalbe’s line method. Mean TM lengths were 811 ± 83 μm and 575 ± 96 μm in the open and closed angle groups, respectively (p < 0.001). Comparing the actual TM heights using Schwalbe’s line method with an updated reference distance significantly increased accuracy to locate the scleral spur (open: 811 μm, closed: 575 μm) when compared with the 1000 μm reference distance (p < 0.001). TM length was significantly different between open and closed angle patients. Further, the reference distance for Schwalbe’s line method should be distinguished according to open and closed angle eyes in order that the scleral spur can be located properly.

Relationship Between Post-Exercise Changes in the Lens and Schlemm's Canal: A Swept-Source Optical Coherence Tomography Study

AIM

To observe post-exercise changes in the lens and Schlemm's canal (SC) in healthy individuals using swept-source optical coherence tomography (SS-OCT).

METHODS

Thirty-five healthy, young individuals were recruited and performed aerobic exercise by jogging for 20 minutes. The SC area, SC perimeter, trabecular meshwork (TM) length, TM thickness, lens vault (LV), and lens thickness (LT) were assessed by SS-OCT before and after exercise.

RESULTS

Following aerobic exercise, SC area (4260.85 ± 1476.02 vs. 5158.24 ± 1527.42 μm², p < 0.001), SC perimeter (349.21 ± 62.22 vs. 391.24 ± 71.77 μm, p < 0.001), TM length (781.16 ± 114.83 vs. 816.46 ± 121.26 μm, p < 0.001), and TM thickness (111.52 ± 19.30 vs. 116.96 ± 17.57 μm, p = 0.004) increased significantly, while LV (-0.134 ± 0.198 vs. -0.195 ± 0.198 mm, p < 0.001) decreased significantly and LT showed no significant post-exercise changes (3.86 ± 0.32 vs. 3.85 ± 0.32 mm, p = 0.801). Moreover, post-exercise changes in SC area were significantly associated with post-exercise changes in LV (β = -6487.83; p = 0.040).

CONCLUSIONS

Aerobic exercise induces both backward axial displacement of the lens and SC expansion. This backward axial displacement of the lens could be an important causative factor of the post-exercise SC expansion via the lens-zonular-ciliotrabecular vector and the connecting fibrils between ciliary body and SC.

Revisiting the Cornea and Trabecular Meshwork Junction With 2-Photon Excitation Fluorescence Microscopy

PURPOSE

To investigate the collagen and elastin architecture at the junction of the human cornea and trabecular meshwork (TM).

METHODS

The cornea, TM, and ciliary body (CB) tendons of unfixed human corneal buttons were imaged with an inverted 2-photon excited fluorescence microscope (FluoView FV-1000; Olympus, Central Valley, PA). The laser (Ti:sapphire) was tuned to 850 nm for 2-photon excitation. Backscatter signals of second harmonic generation and autofluorescence were collected through a 425/30-nm emission filter and a 525/45-nm emission filter, respectively. The second harmonic generation signal corresponds to collagen fibers, and the autofluorescence signal corresponds to elastin-containing tissue. Tissue structure representations were obtained through software-generated reconstructions of consecutive and overlapping (z-stack) images through a relevant sample depth.

RESULTS

Collagen-rich CB tendons insert into the cornea between Descemet membrane (DM) and posterior stroma along with elastin fibers originating from the TM. The CB tendons directly abut DM, and their insertion narrows as they course centrally in the cornea, giving a wedge appearance to these parallel collagen fibers. Approximately 260 μm centrally from the edge of DM, the CB tendons fan out and merge with pre-DM collagen. As the CB tendons enter the cornea, they form a dense collagenous comb-like structure orthogonal to the edge of DM and supported by a delicate elastin network of interwoven fibers originating from the TM.

CONCLUSIONS

Two-photon excited fluorescence microscopy has improved our understanding of the peripheral corneal architecture. CB tendon insertions in this region may contribute to the radial tears encountered when preparing DM endothelial keratoplasty grafts.

Mechanism of the reconstruction of aqueous outflow drainage

Glaucoma is the leading cause of irreversible blindness worldwide. The reconstruction of aqueous outflow drainage (RAOD) has recently been proposed to aid in restoring aqueous outflow drainage in primary open-angle glaucoma. However, the mechanism of RAOD remains to be fully understood. Based on literature review and research studies, the potential mechanisms of RAOD are the following: (i) Circumferential dilation of the Schlemm's canal (SC) and surrounding collector channels. (ii) Instant formation of microcracks through RAOD procedures. (iii) Formation of more pores, and local detachment between the SC endothelium (SCE) and basement membrane. (iv) Activation of stem cells by constant mechanical stress caused by the tensional suture placed at the anterior part of the SC. (v) Reversal of trabecular meshwork (TM) herniation. (vi) Mobilization of the reserve of the aqueous drainage. (vii) Change of SCE phenotype. (viii) Mechanosensing and mechanotransducing of TM.

Schlemm's Canal and Trabecular Meshwork in Eyes with Primary Open Angle Glaucoma: A Comparative Study Using High-Frequency Ultrasound Biomicroscopy

We investigated in vivo changes in Schlemm’s canal and the trabecular meshwork in eyes with primary open angle glaucoma (POAG). Relationships between Schlemm’s canal diameter, trabecular meshwork thickness, and intraocular pressure (IOP) were examined. Forty POAG patients and 40 normal individuals underwent 80-MHz Ultrasound Biomicroscopy examinations. The Schlemm’s canal and trabecular meshwork were imaged in superior, inferior, nasal and temporal regions. Normal individuals had an observable Schlemm’s canal in 80.3% of sections, a meridional canal diameter of 233.0±34.5 μm, a coronal diameter of 44.5±12.6 μm and a trabecular meshwork thickness of 103.9±11.1 μm, in POAG patients, Schlemm’s canal was observable in 53.1% of sections, a meridional canal diameter of 195.6±31.3 μm, a coronal diameter of 35.7±8.0 μm, and a trabecular meshwork thickness of 88.3±13.2 μm, which significantly differed from normal (both p <0.001). Coronal canal diameter (r = -0.623, p < 0.001) and trabecular meshwork thickness (r = -0.663, p < 0.001) were negatively correlated with IOP, but meridional canal diameter was not (r = -0.160, p = 0.156). Schlemm’s canal was observable in 50.5% and 56.6% of POAG patients with normal (<21 mmHg) and elevated (>21 mmHg) IOP, respectively (χ = 1.159, p = 0.282). Coronal canal diameter was significantly lower in the elevated IOP group (32.6±4.9 μm) than in the normal IOP group (35.7±8.0 μm, p < 0.001). This was also true of trabecular meshwork thickness (81.9±10.0 μm vs. 97.1±12.0 μm, p < 0.001). In conclusion, eyes with POAG had fewer sections with an observable Schlemm’s canal. Canal diameter and trabecular meshwork thickness were also lower than normal in POAG patients. Schlemm’s canal coronal diameter and trabecular meshwork thickness were negatively correlated with IOP.