Recent advances in anterior chamber angle imaging

Evaluation of changes of anterior segment parameters in patients with pseudoexfoliation syndrome after cataract surgery using anterior segment optical coherence tomography

The aim of the study was to compare the anterior segment parameters after cataract surgery in pseudoexfoliation syndrome (PEX) and control eyes. We conducted a prospective comparative study of 36 eyes (PEX group), 16 eyes (PEXG group) and 46 eyes (control group) of 98 patients after phacoemulsification with intraocular lens implantation. Before surgery, 1 week, 1 month and 3 months postoperatively, anterior chamber parameters were evaluated by swept source anterior segment optical coherence tomography (AS-OCT). Anterior chamber depth (ACD), angle opening distance (AOD500/750), trabecular-iris space area (TISA500/750), trabecular-iris angle (TIA500/750) and lens vault (LV) were assessed at each study visit. Preoperatively, ACD, AOD500/750 and TISA500/750 were significantly smaller, while LV was significantly greater in PEX and PEXG eyes than in controls. 3 months postoperatively all irido-corneal parameters and ACD were significantly greater in all study groups without intergroup differences. ACD and LV significantly increased in PEX group between 1 and 3 months after surgery while being stable in control group. Relative increases in ACD, AOD500, TISA750, TIA500/750 were significantly higher in PEX and PEXG groups than in controls. Our study finds that ACD and iridocorneal parameters in AS-OCT demonstrated significantly greater relative increases 3 months after phacoemulsification in PEX and PEXG groups than in control eyes. Significantly greater deepening of anterior chamber and opening of the irido-corneal angle may be a reason for different refractive outcomes and IOP control in patients with PEX and PEXG after routine cataract surgery.

The value of virtual glaucoma clinics: a review

Virtual clinics are being utilised to tackle the growing demand for glaucoma healthcare. We conducted a literature search on 28 February 2023 using MEDLINE (PubMed), EMBASE and Web of Science databases. We searched for studies on virtual glaucoma clinics, published in the English language between 2000 and 2023. Studies suggest that virtual glaucoma clinics are a safe and effective alternative to traditional face-to-face clinics for patients with stable and early-to-moderate glaucoma. Patient satisfaction is high across all clinics surveyed. Satisfaction appears to be linked to good communication, trust and improved waiting times. The majority of healthcare professionals are also content with virtual glaucoma clinics. There are no dedicated cost-benefit analyses for virtual glaucoma clinics in the UK. However, virtual clinics in other specialties have reported significant cost savings.

Risk factors associated with haptic malposition in eyes implanted with implantable collamer lenses

PURPOSE

To examine the risk factors for haptic malposition in eyes with implantable collamer lens (ICL).

SETTING

Eye and ENT Hospital, Fudan University, Shanghai, China.

DESIGN

Prospective nonrandomized observational study.

METHODS

This study included 134 (77.9%) of 172 initially enrolled patients who underwent ICL implantation and completed a 1-year follow-up. The extent of haptics present in the ciliary sulcus (ICS) was measured. Patients were categorized based on ICS count (0 to 4). The position of the haptics was quantified as the distance between the iris root and the terminal tip of ICL haptics (iris root to haptic tip, IRH). The related factors to the ICS count and its correlation with the central vault were analyzed.

RESULTS

ICS distribution was 0 ICS in 19 eyes (14.2%), 1 in 22 eyes (16.4%), 2 in 32 eyes (23.9%), 3 in 29 eyes (21.6%), and 4 in 32 eyes (23.9%). Parameters like maximum ciliary body thickness (CBTmax, P = .008), iris-ciliary process distance (ICPD, P < .001), and ciliary process length ( P = .034) varied significantly across ICS groups. A multiple linear regression analysis revealed that the iris-ciliary angle ( P = .006), CBTmax ( P = .007), the distance between the sulcus-to-sulcus plane and the anterior crystalline lens surface (STSL, P = .035), and ICL size ( P = .015) were significantly associated with IRH. Spherical equivalents ( P = .042), STSL ( P = .001), and ICS count ( P = .020) significantly correlated with the central vault.

CONCLUSIONS

Shortened ciliary process is a primary risk for haptic malposition. The ICS count significantly relates to the central vault.

Ophthalmic exam and ophthalmology residents' subspecialty preference

AIM

To evaluate residents' perceptions and attitudes toward the various aspects of a comprehensive ophthalmic examination, and to determine if these factors correlate with their choices for fellowship and future career plans.

METHODS

This is a cross-sectional study. A questionnaire on the perception of the ophthalmic exam was sent via SurveyMonkey to ophthalmology residents throughout Israel. Eighty of them (one-half of all ophthalmology residents in 2019) completed it. The first part related to how they perceived each component of the ophthalmic evaluation. The second part related to their future fellowship plans. The Chi-squared test was used to compare categorical variables and Student's t-test and One-way ANOVA were used to compare continuous variables. Multivariate logistic regression analysis was applied as needed to detect interactions between variables and to exclude confounder effects.

RESULTS

Slit-lamp examination of the anterior and posterior segments ranked as the most likeable aspects, whereas gonioscopy, ocular motility examination and visual acuity assessment were least likeable. Anterior segment and retina subspecialties were the ones most sought after. Forty-nine respondents (61.3%) noted a direct correlation between their preferred parts of comprehensive ophthalmic evaluations and their choice of subspecialty. Perceptions of selected components of those evaluations were significantly associated with responders' intentions to pursue anterior segment, retina, or oculoplastic fellowships (P<0.05).

CONCLUSION

Perspectives of residents toward the ophthalmic examination, and most specifically its individual components, play an important role in their choice of subspecialty training.

Progressive Changes in the Anterior Segment and Their Impact on the Anterior Chamber Angle in Primary Angle Closure Disease

PURPOSE

To investigate longitudinal changes in the anterior segment (AS) using serial optical coherence tomography (OCT) images and determine the impact of these changes on the anterior chamber angle (ACA) in eyes with primary angle closure disease (PACD) treated with laser peripheral iridotomy (LPI).

DESIGN

Retrospective clinical cohort study.

METHODS

This study included 103 patients with PACD who underwent LPI and were followed up by a mean 6.7 ± 1.7 AS-OCT examinations for a mean 6.5 ± 2.9 years. Temporal changes in AS-OCT parameters, including anterior chamber depth (ACD), angle opening distance (AOD750), angle recess area (ARA750), iris thickness (IT750), lens vault (LV), and pupil diameter (PD), were analyzed by multivariate linear mixed effects models (LMEMs).

RESULTS

Multivariate LMEMs showed that decrease in AOD750 was not significant (-1.59 µm/y, P = .222); however, ARA750 decreased over time (-2.3 × 103 µm2/y, P = .033) and SSA showed marginal significance (-0.20°/y, P = .098), and LV increased significantly (11.6 µm/y, P < .001) after LPI. Mean LV change was negatively associated with AOD750, ARA750, and SSA, whereas PD was negatively associated with ARA750 (P < .001 each). PD decreased with aging (-13.7 µm/y, P = .036), accompanied by thinning of IT750 (-1.7 µm/y, P = .063).

CONCLUSIONS

LV tends to increase with aging, which contributes to the shallowing of the anterior chamber and narrowing of ACA in PACD eyes treated with LPI. In the meantime, pupillary constriction and subsequent peripheral iris thinning associated with aging could possibly offset the effect of ACA narrowing.

Comprehensive assessment of the anterior segment in refraction corrected OCT based on multitask learning

Anterior segment diseases are among the leading causes of irreversible blindness. However, a method capable of recognizing all important anterior segment structures for clinical diagnosis is lacking. By sharing the knowledge learned from each task, we proposed a fully automated multitask deep learning method that allows for simultaneous segmentation and quantification of all major anterior segment structures, including the iris, lens, cornea, as well as implantable collamer lens (ICL) and intraocular lens (IOL), and meanwhile for landmark detection of scleral spur and iris root in anterior segment OCT (AS-OCT) images. In addition, we proposed a refraction correction method to correct for the true geometry of the anterior segment distorted by light refraction during OCT imaging. 1251 AS-OCT images from 180 patients were collected and were used to train and test the model. Experiments demonstrated that our proposed network was superior to state-of-the-art segmentation and landmark detection methods, and close agreement was achieved between manually and automatically computed clinical parameters associated with anterior chamber, pupil, iris, ICL, and IOL. Finally, as an example, we demonstrated how our proposed method can be applied to facilitate the clinical evaluation of cataract surgery.

Artificial Intelligence for Anterior Segment Diseases: A Review of Potential Developments and Clinical Applications

Artificial intelligence (AI) technology is promising in the field of healthcare. With the developments of big data and image-based analysis, AI shows potential value in ophthalmology applications. Recently, machine learning and deep learning algorithms have made significant progress. Emerging evidence has demonstrated the capability of AI in the diagnosis and management of anterior segment diseases. In this review, we provide an overview of AI applications and potential future applications in anterior segment diseases, focusing on cornea, refractive surgery, cataract, anterior chamber angle detection, and refractive error prediction.

Evaluations of bridging sutures in preventing iris capture in eyes with intrascleral fixation of implanted intraocular lens

PURPOSE

The study aims to determine the effectiveness of bridging sutures in preventing iris capture and a subsequent reverse pupillary block after an intrascleral fixation of an implanted intraocular lens (IOL).

METHODS

We studied 6 eyes that had an iris capture with reverse pupillary block due to a dislocated IOL after an intrascleral fixation. After the dislocated IOL was repositioned, 10-0 polypropylene sutures were inserted 1.5 mm posterior to the limbus and directed to run between the iris and the IOL. The sutures were placed orthogonal to the haptics of the IOL. Anterior segment optical coherence tomography (AS-OCT) was used in 4 eyes to evaluate the degree of iridodonesis before and after the bridging sutures. The heights of the temporal and nasal sectors of the middle iris from the iris plane (the line between anterior chamber angles) were compared for each 0.2-s AS-OCT image taken immediately after the eye moved from a lateral to a primary position.

RESULTS

None of the eyes had a recurrence of the iris capture after the bridging sutures. The refractive error, anterior chamber depth, and vision were not significantly altered after the bridging sutures were placed. The AS-OCT images showed that the height of the nasal iris was decreased more at 0 s postoperatively blocking the excessive downward movement of the nasal iris but not the iridodonesis.

CONCLUSION

Bridging sutures were effective in preventing iris capture and subsequent reverse pupillary block after an intrascleral fixation of an IOL.

Applications of Artificial Intelligence and Deep Learning in Glaucoma

Diagnosis and detection of progression of glaucoma remains challenging. Artificial intelligence-based tools have the potential to improve and standardize the assessment of glaucoma but development of these algorithms is difficult given the multimodal and variable nature of the diagnosis. Currently, most algorithms are focused on a single imaging modality, specifically screening and diagnosis based on fundus photos or optical coherence tomography images. Use of anterior segment optical coherence tomography and goniophotographs is limited. The majority of algorithms designed for disease progression prediction are based on visual fields. No studies in our literature search assessed the use of artificial intelligence for treatment response prediction and no studies conducted prospective testing of their algorithms. Additional challenges to the development of artificial intelligence-based tools include scarcity of data and a lack of consensus in diagnostic criteria. Although research in the use of artificial intelligence for glaucoma is promising, additional work is needed to develop clinically usable tools.

Expansion of patient eligibility for virtual glaucoma clinics: a long-term strategy to increase the capacity of high-quality glaucoma care

AIMS

The virtual glaucoma clinic (VGC) is a well-established diagnostic pathway for delivery of glaucoma care. Current UK national guidance recommends VGCs for patients with ocular hypertension, glaucoma suspects or early glaucoma. This study evaluates whether expanded eligibility criteria, including other glaucoma phenotypes and disease stages, can deliver safe and effective care with a positive patient experience.

METHODS

Records of over 8000 patients were reviewed in order to determine suitability for VGC attendance using expanded eligibility criteria. Patients with three prior consecutive visits within the glaucoma service were included. Follow-up interval, clinic type, visual acuity (VA), intraocular pressure (IOP) and visual field performance were recorded. Patient satisfaction was recorded for a sample of 118 patients.

RESULTS

2017 patients over 31 months were included. Two-thirds of eyes had ocular comorbidities, a fifth of eyes had undergone prior cataract surgery and 10% of eyes had undergone a prior laser treatment for glaucoma. After three visits, 32% of patients remained in the VGC, 42% were seen in face-to-face clinics and 25% were discharged. There were no clinically significant changes in VA, IOP and visual field performance during follow-up. 72% of patients expressed a preference to continue their care within VGCs.

CONCLUSIONS

This study demonstrates that VGCs with expanded patient eligibility criteria can deliver high-quality glaucoma care that is safe, effective and with high levels of patient satisfaction. This approach provides a long-term solution to adapt delivery of glaucoma care to our expanding and ageing population.

Updates on the Diagnosis and Management of Glaucoma

Glaucoma is the leading cause of blindness throughout the world (after cataracts); therefore, general physicians should be familiar with the diagnosis and management of affected patients. Glaucomas are usually categorized by the anatomy of the anterior chamber angle (open vs narrow/closed), rapidity of onset (acute vs chronic), and major etiology (primary vs secondary). Most glaucomas are primary (ie, without a contributing comorbidity); however, several coexisting ophthalmic conditions may serve as the underlying etiologies of secondary glaucomas. Chronic glaucoma occurs most commonly; thus, regular eye examinations should be performed in at-risk patients to prevent the insidious loss of vision that can develop before diagnosis. Glaucoma damages the optic nerve and retinal nerve fiber layer, leading to peripheral and central visual field defects. Elevated intraocular pressure (IOP), a crucial determinant of disease progression, remains the only modifiable risk factor; thus, all current treatments (medications, lasers, and operations) aim to reduce the IOP. Pharmacotherapy is the usual first-line therapy, but noncompliance, undesirable adverse effects, and cost limit effectiveness. Laser and surgical treatments may lower IOP significantly over long periods and may be more cost effective than pharmacotherapy, but they are plagued by greater procedural risks and frequent treatment failures. Traditional incisional procedures have recently been replaced by several novel, minimally invasive glaucoma surgeries with improved safety profiles and only minimal decreases in efficacy. Minimally invasive glaucoma surgeries have dramatically transformed the surgical management of glaucoma; nevertheless, large, randomized trials are required to assess their long-term efficacy.

Deep learning-based classification of the anterior chamber angle in glaucoma gonioscopy

In the proposed network, the features were first extracted from the gonioscopically obtained anterior segment photographs using the densely-connected high-resolution network. Then the useful information is further strengthened using the hybrid attention module to improve the classification accuracy. Between October 30, 2020, and January 30, 2021, a total of 146 participants underwent glaucoma screening. One thousand seven hundred eighty original images of the ACA were obtained with the gonioscope and slit lamp microscope. After data augmentation, 4457 images are used for the training and validation of the HahrNet, and 497 images are used to evaluate our algorithm. Experimental results demonstrate that the proposed HahrNet exhibits a good performance of 96.2% accuracy, 99.0% specificity, 96.4% sensitivity, and 0.996 area under the curve (AUC) in classifying the ACA test dataset. Compared with several deep learning-based classification methods and nine human readers of different levels, the HahrNet achieves better or more competitive performance in terms of accuracy, specificity, and sensitivity. Indeed, the proposed ACA classification method will provide an automatic and accurate technology for the grading of glaucoma.

Moving beyond the Slit-Lamp Gonioscopy: Challenges and Future Opportunities

After almost a century from its introduction in clinical practice, slit-lamp gonioscopy is still considered the reference standard for evaluating the anterior chamber angle (ACA). Gonioscopy is essential for diagnosing angle closure disease, and ACA features are included in glaucoma’s diagnostics and treatments algorithms. However, shortcomings of slit-lamp gonioscopy include a steep learning curve, lack of agreement between examiners and poor documentation. Thanks to advances in miniaturization and computing, new instruments for digital gonioscopy have been developed and marketed. This narrative review focuses on the Gonioscope GS-1, which permits semi-automated circumferential documentation of the ACA in real-colour photographs. Advantages and disadvantages of GS-1 compared with slit-lamp gonioscopy and other ACA imaging technologies such as optical coherence tomography are discussed. Finally, potential opportunities offered by this device for telemedicine, virtual clinics, and automatic classification with deep learning are presented.

Dynamic volume-rendered optical coherence tomography pupillometry

PURPOSE

To assess intrapupillary space (IPS) changes in healthy subjects with regard to decreased iris motility in patients with pseudoexfoliation glaucoma (PEXG) or non-arteritic anterior ischaemic optic neuropathy (NAION) in a feasibility study in a clinical environment.

METHODS

Scotopic and photopic IPS measurements using three-dimensionally rendered swept-source optical coherence tomography (SS-OCT) data were obtained and compared for all subjects. Intrapupillary space (IPS) parameters were evaluated such as absolute volumetric differences, relative light response for volumetric ratios and pupillary ejection fraction (PEF) for functional contraction measurements.

RESULTS

From a total of 122 IPS from 66 subjects, 106 IPS were eligible for comparison providing values for 72 normal, 30 PEXG and 4 NAION eyes. In healthy, PEXG and NAION subjects, scotopic overall mean IPS was 8.90, 3.45 and 4.16 mm³ , and photopic overall mean IPS was 0.87, 0.74 and 1.13 mm³ , respectively. Three-dimensional contractility showed a mean absolute difference of 8.03 mm³ for normals (defined as 100% contractility), 2.72 mm³ for PEXG (33.88% of normal) and 3.03 mm³ for NAION (38.50% of normal) with a relative light response ratio between scotopic and photopic volumes of 10.26 (100%), 4.69 (45.70%) and 3.67 (35.78%), respectively. Pupillary ejection fraction (PEF) showed a contractile pupillary emptying of 88.11% for normals, 76.92% for PEXG and 70.91% for NAION patients.

CONCLUSION

This 3D pupillometry OCT assessment allows for quantitative measurements of pupil function, contractility and response to light. More specifically, PEF is presented as a potential (neuro)-pupillary outcome measure that could be useful in the monitoring of ophthalmic disorders that affect pupillary function.

Assessment of anterior chamber angle changes after phacoemulsification with swept-source OCT

AIM

To assess the changes of anterior chamber angle in patients with shallow anterior chamber after phacoemulsification combined with intraocular lens (IOL) implantation, based on anterior segment swept-source optical coherence tomography (AS-SS-OCT) measurements.

METHODS

This was a prospective case control study; sixty eyes of sixty case were scheduled for cataract surgery with normal intraocular pressure (IOP). Based on anterior chamber depth (ACD) and gonioscopy findings, the eyes were divided into two groups: group of shallow anterior chamber and narrow angle (SAC group, 30 eyes); and group of normal anterior chamber group with wide angle (NAC group, 30 eyes). Measurements of ACD, anterior chamber volume (ACV), iris volume (IV), lens vault (LV), angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), and trabecular iris angle (TIA) were conducted in each group before and 3mo after surgery.

RESULTS

There was no significant difference in age, axial length (AL), corneal curvature, corneal diameter, intraocular pressure, and IV between two groups before surgery, except for the LV (P=0.000). ACD and ACV were prominently larger in the NAC group than the SAC group 3mo after operation (3.69±0.38 vs 3.85±0.39 mm, P=0.025; 161.37±19.47 vs 178.26±20.30 mm³, P=0.002). AOD750, ARA750 in nasal and inferior quadrants, TISA750 in all quadrants except temporal, and TIA750 in all quadrants in SAC group were significantly smaller than those in NAC group after operation (all P<0.05).

CONCLUSION

Cataract surgery can deepen anterior chamber and increase the width of anterior chamber angle in Chinese subjects, but the angle related parameters including AOD750, ARA750, TISA750, TIA, TISA750, and ACV in patients with shallow anterior chamber and narrow angle do not reach the normal level.

Repeatability and Reproducibility of Anterior Chamber Angle Measurement with Swept-Source Optical Coherence Tomography in Patients with Primary Angle Closure Suspect

Purpose: To evaluate the inter- and intra-observer reliability of anterior chamber (AC) angle measurements obtained by swept-source optical coherence tomography (SS-OCT).Methods: Forty-eight consecutive patients diagnosed with primary angle closure suspect (PACS) were included. Three masked observers at different training levels (one glaucoma specialist, one ophthalmology resident, and one pre-medical college student) measured 192 SS-OCT images of the PACS patients. One observer (the glaucoma specialist) repeated measurements 1 week later. SS-OCT parameters included: Anterior segment volume, including corneal, AC, and iris volume; anterior segment dimensions, including AC depth and width (ACD, ACW), and lens vault (LV); and angle parameters, including angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), and the trabecular iris angle (TIA). Intraclass correlation coefficients (ICCs) were used to measure reliability.Results: For inter-observer reproducibility, ICCs of corneal, AC, and iris volumes were 0.952 to 0.998. ICCs of ACD at all axes were above 0.989. ICCs of ACW and LV were smallest in the 90°-270° axis (0.751 and 0.768) but not significantly different from other axes. ARA, TISA, and TIA at all angles had significantly smallest ICCs 250 µm from the scleral spur compared with 500 µm and 750 µm. The ICCs comparing observers with different training levels had similar ranges and followed similar trends. For intra-observer repeatability, the smallest ICC was 0.843. Decreasing AC depth correlated with increased inter-observer reproducibility.Conclusions: We found excellent intra-observer repeatability for all SS-OCT parameters. Angle measurements have more variation among the observers when taken 250 µm from the scleral spur. Shallow AC might lead to more variability for angle parameters. Non-expert observers may be recruited for high-quality image grading with standard training.

Diagnostic accuracy of swept source optical coherence tomography classification algorithms for detection of gonioscopic angle closure

PURPOSE

To evaluate the performance of swept source optical coherence tomography (SS-OCT) to detect gonioscopic angle closure using different classification algorithms.

METHODS

This was a cross-sectional study of 2028 subjects without ophthalmic symptoms recruited from a community-based clinic. All subjects underwent gonioscopy and SS-OCT (Casia, Tomey Corporation, Nagoya, Japan) under dark room conditions. For each eye, 8 out of 128 frames (22.5° interval) were selected to measure anterior chamber parameters namely anterior chamber width, depth, area and volume (ACW, ACD, ACA, and ACV), lens vault (LV), iris curvature (IC), iris thickness (IT) from 750 µm and 2000 µm from the scleral spur, iris area and iris volume. Five diagnostic algorithms-stepwise logistic regression, random forest, multivariate adaptive regression splines, recursive partitioning and Naïve Bayes were evaluated for detection of gonioscopic angle closure (defined as ≥2 closed quadrants). The performance of the horizontal frame was compared with that of other meridians.

RESULTS

Data from 1988 subjects, including 143 (7.2%) with gonioscopic angle closure, were available for analysis. They were divided into two groups: training (1391, 70%) and validation (597, 30%). The best algorithm for detecting gonioscopic angle closure was stepwise logistic regression with an area under the curve of 0.91 (95% CI 0.88 to 0.93) using all parameters, and 0.88 (95% CI 0.82 to 0.93) using only ACA, LV and IC of the horizontal meridian scan.

CONCLUSIONS

A stepwise logistic regression model incorporating SS-OCT measurements has a high diagnostic ability to detect gonioscopic angle closure.

Association Between Anterior Chamber Angle and Corneal Endothelial Cell Density in Chronic Angle Closure

Purpose

To study the association between corneal endothelial cell density (ECD) and degree of anterior chamber angle (ACA) opening in eyes with chronic angle closure glaucoma.

Methods

The study was conducted at JEC Eye Hospitals in Indonesia. Treatment-naïve patients aged ≥40 years with IOP >21 mmHg and peripheral anterior chamber depth (ACD) grade 2 or less by Van Herick's technique were recruited. Trabecular iris angle (TIA; degree) was measured using anterior segment optical coherence tomography (AS-OCT) and classified as: grade 1 ≤10°, grade 2 11-20°, and grade 3 >20°. Noncontact specular microscopy was performed, and the following corneal parameters were obtained:ECD (cells/mm²), coefficient of variation (CV; μm²/cell), percentage of hexagonal cells, and central corneal thickness (CCT; μm).

Results

A total of 52 eyes from 52 subjects were recruited (16 grade 1 TIA, 24 grade 2 TIA, and 12 grade 3 TIA). Presenting IOP was not significantly different between groups. The median central corneal ECD was 2684.5 (1433-2934), 2587.0 (1902-3103), and 2441.0 (1659-3005) cells/mm² in grade 1, 2, and 3 TIA, respectively, with no significant differences across the groups (P = 0.67). The CV was lowest in grade 3 TIA (36.4 ± 7.2 μm2/cell), and highest in grade 1 TIA (38.3 ± 9.6 μm2/cell), but the differences were not significant (P = 0.74). Likewise, the percentage of hexagonality and CCT was not significantly different. TIA was not correlated with IOP but was modestly correlated with age.

Conclusion

The corneal ECD and morphological characteristics such as CV and hexagonality were not significantly different across various TIA grading in chronic angle closure. This may reflect the lack of chronic and gradual IOP insult on corneal endothelial parameters as TIA did not show direct effect towards IOP.

Towards 'automated gonioscopy': a deep learning algorithm for 360° angle assessment by swept-source optical coherence tomography

AIMS

To validate a deep learning (DL) algorithm (DLA) for 360° angle assessment on swept-source optical coherence tomography (SS-OCT) (CASIA SS-1000, Tomey Corporation, Nagoya, Japan).

METHODS

This was a reliability analysis from a cross-sectional study. An independent test set of 39 936 SS-OCT scans from 312 phakic subjects (128 SS-OCT meridional scans per eye) was analysed. Participants above 50 years with no previous history of intraocular surgery were consecutively recruited from glaucoma clinics. Indentation gonioscopy and dark room SS-OCT were performed. Gonioscopic angle closure was defined as non-visibility of the posterior trabecular meshwork in ≥180° of the angle. For each subject, all images were analysed by a DL-based network based on the VGG-16 architecture, for gonioscopic angle-closure detection. Area under receiver operating characteristic curves (AUCs) and other diagnostic performance indicators were calculated for the DLA (index test) against gonioscopy (reference standard).

RESULTS

Approximately 80% of the participants were Chinese, and more than half were women (57.4%). The prevalence of gonioscopic angle closure in this hospital-based sample was 20.2%. After analysing a total of 39 936 SS-OCT scans, the AUC of the DLA was 0.85 (95% CI:0.80 to 0.90, with sensitivity of 83% and a specificity of 87%) to classify gonioscopic angle closure with the optimal cut-off value of >35% of circumferential angle closure.

CONCLUSIONS

The DLA exhibited good diagnostic performance for detection of gonioscopic angle closure on 360° SS-OCT scans in a glaucoma clinic setting. Such an algorithm, independent of the identification of the scleral spur, may be the foundation for a non-contact, fast and reproducible 'automated gonioscopy' in future.

Anterior Chamber Angle Assessment Techniques: A Review

Assessment of the anterior chamber angle (ACA) is an essential part of the ophthalmological examination. It is intrinsically related to the diagnosis and treatment of glaucoma and has a role in its prevention. Although slit-lamp gonioscopy is considered the gold-standard technique for ACA evaluation, its poor reproducibility and the long learning curve are well-known shortcomings. Several new imaging techniques for angle evaluation have been developed in the recent years. However, whether these instruments may replace or not gonioscopy in everyday clinical practice remains unclear. This review summarizes the last findings in ACA evaluation, focusing on new instruments and their application to the clinical practice. Special attention will be given to the comparison between these new techniques and traditional slit-lamp gonioscopy. Whereas ultrasound biomicroscopy and anterior segment optical coherence tomography provide quantitative measurements of the anterior segment’s structures, new gonio-photographic systems allow for a qualitative assessment of angle findings, similarly to gonioscopy. Recently developed deep learning algorithms provide an automated classification of angle images, aiding physicians in taking faster and more efficient decisions. Despite new imaging techniques made analysis of the ACA more objective and practical, the ideal method for ACA evaluation has still to be determined.