Dynamic Changes in Schlemm Canal and Iridocorneal Angle Morphology During Accommodation in Children With Healthy Eyes: A Cross-Sectional Cohort Study

Evaluation of different OCT systems in quantitative imaging of human Schlemm's canal

We examined the performance of human Schlemm's canal (SC) imaging using different OCT devices: CIRRUS 5000 (840 nm, spectral-domain (SD)-OCT), PLEX Elite 9000 (1060 nm, swept-source (SS)-OCT) and CASIA SS-1000 (1310 nm, SS-OCT), and analyzed potential impact factors on visualization and the quantitative assessment of SC morphology in a pilot study. Ten healthy subjects were imaged using three OCT devices by a single experienced operator on the same day. Each eye underwent two cubic scans by each device, one on nasal and the other on temporal quadrant. The B-scan showing the largest SC was manually selected for processing. Four quantitative metrics, including one morphological metric as cross-sectional area (CSA), and three performance metrics as contrast, continuity, and coverage, were derived from the datasets. Repeated-measures ANOVA was used to investigate the difference between these parameters from the three devices (P < 0.05). We found the CSA measured from CIRRUS was significantly larger than PLEX, followed by CASIA. The contrast was highest in CIRRUS, followed by PLEX and CASIA. The coverage was also higher in CIRRUS as compared to PLEX and CASIA. No significant difference was seen in the continuity from the three devices. In summary, we showed the measurements from the three devices were not interchangeable.

Open-source deep learning-based automatic segmentation of mouse Schlemm's canal in optical coherence tomography images

The purpose of this study was to develop an automatic deep learning-based approach and corresponding free, open-source software to perform segmentation of the Schlemm's canal (SC) lumen in optical coherence tomography (OCT) scans of living mouse eyes. A novel convolutional neural network (CNN) for semantic segmentation grounded in a U-Net architecture was developed by incorporating a late fusion scheme, multi-scale input image pyramid, dilated residual convolution blocks, and attention-gating. 163 pairs of intensity and speckle variance (SV) OCT B-scans acquired from 32 living mouse eyes were used for training, validation, and testing of this CNN model for segmentation of the SC lumen. The proposed model achieved a mean Dice Similarity Coefficient (DSC) of 0.694 ± 0.256 and median DSC of 0.791, while manual segmentation performed by a second expert grader achieved a mean and median DSC of 0.713 ± 0.209 and 0.763, respectively. This work presents the first automatic method for segmentation of the SC lumen in OCT images of living mouse eyes. The performance of the proposed model is comparable to the performance of a second human grader. Open-source automatic software for segmentation of the SC lumen is expected to accelerate experiments for studying treatment efficacy of new drugs affecting intraocular pressure and related diseases such as glaucoma, which present as changes in the SC area.

Disease progression pathways of wet AMD: opportunities for new target discovery

INTRODUCTION

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness among people age 60 years or older in developed countries. Current standard-of-care anti-vascular endothelial growth factor (VEGF) therapy, which inhibits angiogenesis and vascular permeability, has been shown to stabilize choroidal neovascularization and increase visual acuity in neovascular AMD. However, therapeutic limitations of anti-VEGF therapy include limited durability with consequent need for frequent intravitreal injections, and a ceiling of efficacy. Current strategies under investigation include targeting VEGF-C and VEGF-D, integrins, tyrosine kinase receptors, and the Tie2/angiopoietin-2 pathway. A literature search was conducted through November 30, 2021 on PubMed, Medline, Google Scholar, and associated digital platforms with the following keywords: wet macular degeneration, age-related macular degeneration, therapy, VEGF-A, VEGF-C, VEGF-D, integrins, Tie2/Ang2, and tyrosine kinase inhibitors.

AREAS COVERED

The authors provide a comprehensive review of AMD disease pathways and mechanisms involved in wet AMD as well as novel targets for future therapies.

EXPERT OPINION

With novel targets and advancements in drug delivery, there is potential to address treatment burden and to improve outcomes for patients afflicted with neovascular AMD.

The Relationship Between Age and the Morphology of the Crystalline Lens, Ciliary Muscle, Trabecular Meshwork, and Schlemm's Canal: An in vivo Swept-Source Optical Coherence Tomography Study

Purpose: To evaluate the effects of age on the morphologies of the crystalline lens, ciliary muscle (CM), Schlemm’s canal (SC), and trabecular meshwork (TM) using swept-source optical coherence tomography (SS-OCT).

Methods: Images of the crystalline lens and iridocorneal angle were obtained in healthy participants’ eyes using SS-OCT. Morphological parameters of the crystalline lens, CM, and TM/SC were measured, and the relationship between these parameters and age was evaluated.

Results: A total of 62 healthy participants were enrolled, with an age range of 7–79 years. With adjustments for the effects of axial length and sex, both the nasal and temporal SC cross-sectional areas (CSA) and the cross-sectional area of the CM (CMA), distance from the scleral spur to the inner apex of the ciliary muscle (IA-SS), and nasal SC volume were negatively correlated with age (P ≤ 0.041). Meanwhile, the lens thickness (LT) (P < 0.001) and lens vault (LV) (P < 0.001) were positively correlated with age, and the radius of the curvature of the anterior lens (ALR) was negatively correlated with age (P < 0.001).

Conclusion: Increasing age was associated with a thicker crystalline lens, a steeper anterior lens curvature, an anteriorly located and smaller CM, and a narrower SC.

Clinical Trial Registration:https://register.clinicaltrials.gov/prs/app/action/Select Protocol?sid=S000A3JZ&selectaction=Edit&uid=U00019K7&ts=4&cx=-c5xxp8, identifier [NCT04576884].

Changes in Iridocorneal Angle Configuration and Intraocular Pressure during Smartphone Use under Room Light

Purpose: To investigate changes in intraocular pressure (IOP) and iridocorneal angle (ICA) configuration during smartphone use under room light. Methods: We included healthy adults aged 19-35 years with no ophthalmological abnormalities. All read text on a smartphone for 6 minutes under room light. IOP was measured via rebound tonometry at baseline and at 2, 4, and 6 minutes. ICA images were obtained via anterior segment optical coherence tomography after each IOP measurement. After 6 minutes, participants stopped reading text and rested for 2 minutes. IOP was then measured again. Results: The IOP significantly increased at 2, 4, and 6 minutes of reading compared to baseline (<i>p</i> < 0.001) but recovered to baseline after 2 minutes of rest (<i>p</i> = 1.000). The anterior chamber depth decreased significantly, and the anterior chamber angle width increased after 6 minutes of smartphone reading (both <i>p</i> < 0.05). Conclusions: IOP increased when reading smartphone text under room light but the ICA did not change. Prolonged smartphone reading is inappropriate for a patient at risk of glaucoma or glaucoma progression. Such patients should be cautioned.

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.

Progress in the basic and clinical research on the Schlemm's canal

Glaucoma is a leading cause of irreversible blindness in the world. Intraocular pressure (IOP) plays a key role in glaucoma development and progression. Schlemm's canal (SC), an important structure of the anterior chamber angle, regulates the flow of aqueous humor and maintains IOP. Because of its special function of aqueous outflow, the SC has been intensive investigated recently. Several characteristics of SC in anatomy, physiology and pathophysiology have been revealed. Compare to normal, glaucomatous SC cells are more sensitive to substrate stiffness, have higher stiffness and and lower porosity leading to higher outflow resistance. And SC collapse caused by acute IOP increase is partially or totally reversal. With advanced inspection techniques, high-quality images of the SC can be obtained in vivo, which facilitates SC quantitative measurements clinically and allows us to investigate a new therapy paradigm for glaucoma. In this review, we summarize the basic and clinical research that focused on mechanisms of aqueous outflow resistance and SC changes in physiological, pathological, and post-treatment states.

Glaucoma following cataract surgery in the first 2 years of life: frequency, risk factors and outcomes from IoLunder2

Background

We investigated glaucoma related adverse events, predictors and impact at 5 years following surgery in the IoLunder2 cohort

Methods

Population based observational cohort study of children undergoing cataract surgery aged 2 years or under between January 2009 and December 2010. Glaucoma was defined using internationally accepted taxonomies based on the consequences of elevated intraocular pressure (IOP). Glaucoma related adverse events were any involving elevated IOP. Multivariable analysis was undertaken to investigate potential predictors of secondary glaucoma with adjustment for within-child correlation in bilateral cataract. Unilateral and bilateral cataract were analysed separately.

Results

Complete follow-up data were available for 235 of 254, 93% of the inception cohort. By 5 years after primary cataract surgery, 20% of children with bilateral cataract and 12% with unilateral had developed secondary glaucoma. Glaucoma related complications had been diagnosed in 24% and 36% of children, respectively. Independent predictors of glaucoma were younger age at surgery (adjusted OR for reduction of week in age: 1.1, 95%C I 1.1 to 1.2, p<0.001); the presence of significant ocular comorbidity (adj OR 3.2, 95% CI 1.1 to 9.6, p=0.01); and shorter axial length (adj OR for each mm 1.7, 95% CI 10.0 to 1, p=0.05) for bilateral cataract. Shorter axial length was the single independent factor in unilateral disease (adj OR 9.6, 95% CI 1.7 to 52, p=0.009)

Conclusions

Both younger age at surgery (the strongest marker of ocular ‘immaturity’) and smaller ocular size (a marker of both immaturity and developmental vulnerability) can be used to identify those at greatest risk of glaucoma due to early life cataract surgery.

Optical Coherence Tomography Findings After Childhood Lensectomy

Purpose

To explore the impact of childhood lensectomy on posterior segment development.

Methods

Cross-sectional observational study at children's eye clinics at a tertiary referral center in London, UK. We included 45 children age 4 to 16 years with healthy eyes and 38 who had undergone lensectomy. We acquired posterior segment optical coherence tomography scans of both eyes. We used parametric and nonparametric tests in SPSS24 for the comparison of parameters between groups and within individuals; a P value less than 0.05 was considered significant. The main outcome measures were foveal pit depth and subfoveal choroidal thickness (CT). Secondary outcomes were inner and outer ring CT and photoreceptor layer parameters, macular and peripapillary retinal nerve fiber layer thickness.

Results

Foveal pit depth and subfoveal CT are significantly reduced in eyes that have undergone lensectomy compared with nonoperated eyes. Inner ring CT and outer ring CT are reduced. Foveal inner retinal layer thickness is increased. Mean inner retinal and outer nuclear layer thickness are not affected.

Conclusions

Childhood lensectomy is associated with a reduction in developmental foveal pit deepening and lack of developmental thickening of the posterior choroid. Mechanical and optical disruption of foveal and subfoveal choroidal development may affect structural foveal development after childhood lensectomy.

Comparative Intraoperative Anterior Segment OCT Findings in Pediatric Patients with and without Glaucoma

PURPOSE

To compare the angle structures during surgery using anterior segment (AS) OCT in children with and without glaucoma.

DESIGN

Prospective comparative study, with single masked grader evaluating AS OCT images.

PARTICIPANTS

This study included a total of 44 eyes of 8 children with glaucoma and 14 children without glaucoma undergoing ophthalmic surgery with general anesthesia. The median age for the glaucoma group was 6 months (range, 0.5-108 months), and that for the nonglaucoma group was 42 months (range, 14-95 months).

METHODS

An Envisu C2300 handheld OCT with a high-resolution AS lens was used to capture videos of temporal and nasal quadrant anterior chamber angles from each eye. Still images of the temporal and nasal angles were selected and then graded by a masked ophthalmologist examiner to determine whether Schlemm's canal (SC) was visible, if abnormal tissue was present in the angle, and whether intrascleral lumens were present. Clinical correlation with severity of glaucoma was performed after AS OCT images were graded.

MAIN OUTCOME MEASURES

Presence or absence of SC on AS OCT in glaucomatous and nonglaucomatous eyes.

RESULTS

Schlemm's canal was present in 7 of 13 glaucomatous eyes compared with 27 of 27 nonglaucomatous eyes. In patients with unilateral glaucoma, absence of SC was noted only in the affected eye. Eight eyes with glaucoma showed abnormal tissue over the angle and SC. Intrascleral lumen and collector channels were found in both groups. Two patients with severe stenosis of SC during glaucoma angle surgery showed absent SC on AS OCT.

CONCLUSIONS

Intraoperative AS OCT identified differences in the presence and characteristics of SC and the anterior chamber angle in pediatric patients with and without glaucoma. Further studies are needed to determine clinical correlation.