Qualitative evaluation of anterior segment in angle closure disease using anterior segment optical coherence tomography

Automated classification of angle-closure mechanisms based on anterior segment optical coherence tomography images via deep learning

Purpose

To develop and validate deep learning algorithms that can identify and classify angle-closure (AC) mechanisms using anterior segment optical coherence tomography (AS-OCT) images.

Methods

This cross-sectional study included participants of the Handan Eye Study aged ≥35 years with AC detected via gonioscopy or on the AS-OCT images. These images were classified by human experts into the following to indicate the predominant AC mechanism (ground truth): pupillary block, plateau iris configuration, or thick peripheral iris roll. A deep learning architecture, known as comprehensive mechanism decision net (CMD-Net), was developed to simulate the identification of image-level AC mechanisms by human experts. Cross-validation was performed to optimize and evaluate the model. Human-machine comparisons were conducted using a held-out and separate test sets to establish generalizability.

Results

In total, 11,035 AS-OCT images of 1455 participants (2833 eyes) were included. Among these, 8828 and 2.207 images were included in the cross-validation and held-out test sets, respectively. A separate test was formed comprising 228 images of 35 consecutive patients with AC detected via gonioscopy at our eye center. In the classification of AC mechanisms, CMD-Net achieved a mean area under the receiver operating characteristic curve (AUC) of 0.980, 0.977, and 0.988 in the cross-validation, held-out, and separate test sets, respectively. The best-performing ophthalmologist achieved an AUC of 0.903 and 0.891 in the held-out and separate test sets, respectively. And CMD-Net outperformed glaucoma specialists, achieving an accuracy of 89.9 % and 93.0 % compared to 87.0 % and 86.8 % for the best-performing ophthalmologist in the held-out and separate test sets, respectively.

Conclusions

Our study suggests that CMD-Net has the potential to classify AC mechanisms using AS-OCT images, though further validation is needed.

Changes in Anterior Segment Parameters After Laser Peripheral Iridotomy in Caucasian Eyes With Different Primary Angle Closure Mechanisms

PRCIS

Subgrouping of angle closure mechanisms based on the swept-source optical coherence tomography images may help to identify the predominant underlying anatomic mechanism, evaluate personal treatment, and improve the better outcomes.

PURPOSE

The purpose of this study was to evaluate changes in anterior segment parameters in Caucasian eyes with different angle closure mechanisms before and after laser peripheral iridotomy (LPI).

METHODS

Sixty-six subjects underwent swept-source optical coherence tomography (CASIA, Tomey Corporation) angle imaging in the dark before and 7 days after LPI. On the basis of the baseline swept-source optical coherence tomography images, the eyes were categorized into 4 angle closure mechanisms, namely pupillary block (PB), plateau iris configuration (PIC), thick peripheral iris (TPI), and large lens vault (LLV). Sixteen out of 128 cross-sectional images (11.25 degrees apart) per volume scan were selected for analysis. We used a generalized estimating equation to compare quantitative parameters among angle closure mechanisms and between before and after LPI after adjusting the intereye correlation.

RESULTS

The mean age of subjects was 67.7±9.2 years, with the majority being female (82.2%). One hundred twenty-nine eyes (67 primary angle closure suspects, 34 primary angle closure, and 28 primary angle closure glaucoma) were categorized into PB (n=71, 55%), PIC (n=40, 31%), TPI (n=14, 10.9%), and LLV (n=4, 3.1%). Anterior chamber depth was the shallowest in the LLV, followed by TPI, PB, and PIC group at baseline. Widening of the angle and reduction of the iris curvature (IC) due to LPI were observed in all groups (all P <0.01). When compared to the PB group, the LPI-induced angle widening in the TPI group was significantly less even though the iris curvature reduction in the TPI group was greater (all P <0.05).

CONCLUSIONS

In patients with angle closure, anterior segment morphology and LPI-induced angle widening were different among the various angle closure mechanisms.

Classification of Angle Closure Severity by Hierarchical Cluster Analysis of Ocular Biometrics in the Dark and Light

Purpose

The purpose of this study was to investigate the classification of angle closure eyes based on hierarchical cluster analysis of ocular biometrics measured in the dark and light using anterior segment optical coherence tomography (AS-OCT).

Methods

Participants of the Chinese American Eye Study received complete eye examinations to identify primary angle closure suspects (PACS) and primary angle closure without/with glaucoma (PAC/G). AS-OCT was performed in the dark and light. Biometric parameters describing the angle, iris, lens, and anterior chamber were analyzed. Hierarchical clustering was performed using Ward's method. Post hoc logistic regression models were developed to identify biometric predictors of angle closure staging.

Results

Analysis of 159 eyes with PACS (N = 120) or PAC/G (N = 39) produced 2 clusters in the dark and light. In both analyses, cluster 1 (N = 132 in the dark and N = 126 in the light) was characterized by smaller angle opening distance (AOD)750 and trabecular iris space area (TISA)750, greater iris curvature (IC), and greater lens vault (LV; P < 0.001) than cluster 2. The proportion of PAC/PACG to PACS eyes was significantly higher in cluster 1 than 2 in the light (36:90 and 3:30, respectively; P = 0.02), but not the dark (36:96 and 3:24, respectively; P = 0.08). On multivariable regression analyses, smaller TISA750 (odds ratio [OR] = 0.84 per 0.01 mm2) and AOD750 (OR = 0.93 per 0.01 mm) in the light and smaller TISA750 (OR = 0.86 per 0.01 mm2) in the dark conferred higher risk of PAC/G (P ≤ 0.02).

Conclusions

Unsupervised cluster analysis of ocular biometrics can classify angle closure eyes by severity. Static biometrics measured in the light and dark are both predictive of PAC/G.

Translational Relevance

Clustering of biometrics measured in the light could provide an alternative source of information to risk-stratify angle closure eyes for more severe disease.

One-year outcomes of combined phacoemulsification and viscogoniosynechialysis with and without endoscopic cyclophotocoagulation in primary angle-closure glaucoma

PURPOSE

To compare the outcomes of combined phacoemulsification and viscogoniosynechialysis (VGSL) with and without endoscopic cyclophtocoagulation (ECP) in primary angle-closure glaucoma (PACG).

METHODS

In this prospective interventional case series 52 eyes of 50 patients were enrolled. Twenty-seven eyes underwent combined phacoemulsification and VGSL (PV group) and 25 eyes underwent the same procedure plus circumferential ECP (PVE group). All eyes were followed 1 day, 1 week, 3 months, 6 months, and 1 year after the procedure. Intraocular pressure and antiglaucoma medications were compared between and within groups using generalized estimating equations. Kaplan-Meier survival analysis was carried out to compare intensity to failure between groups.

RESULTS

The mean ± SD age was 63.23 ± 6.87 years and 50% of the cases were male in the entire group. Intraocular pressure (IOP) and antiglaucoma medications were significantly reduced at all time points in comparison with the baseline in both groups (p < 0.05). There was no significant difference between groups in either IOP or medications at specific time points (p > 0.05). One eye in each group developed a fibrinous reaction in the postoperative period. There was no statistically significant difference between groups regarding the intensity to failure (P = 0.169).

CONCLUSION

There were no significant differences in IOP and medication reduction between groups. Also, the complications were comparable between groups.

Assessment of Iridotrabecular Contact and Its Association With Intraocular Pressure After Phacoemulsification in Primary Angle Closure

PURPOSE

To investigate the association between the quantitative assessment of iridotrabecular contact (ITC), measured by swept-source anterior segment optical coherence tomography (SS AS-OCT), and intraocular pressure (IOP) control after phacoemulsification in patients with primary angle closure disease (PACD).

DESIGN

Retrospective, clinical cohort study.

METHODS

Preoperative and postoperative anterior chamber angle parameters were measured using SS AS-OCT. IOP was measured preoperatively and until 6 months postoperatively. Percent IOP reduction and fluctuation after surgery were calculated, and their relationships with SS AS-OCT parameters were assessed by correlation analyses and locally weighted scatterplot smoothing (LOWESS) regression with change-point analysis.

RESULTS

A total of 51 eyes of 51 PACD patients were included. Preoperative ITC index and area (r = 0.626, r = 0.551), as well as changes in ITC index and area (r = 0.632, r = 0.543) after surgery, were significantly correlated with postoperative IOP reduction, after adjusting for age and gender (all P <.001). Higher postoperative ITC index (r = 0.405, P = .005) and ITC area (r = 0.460, P = 0.001) were associated with greater postoperative IOP fluctuations. Change points on LOWESS curves were observed for preoperative ITC index (33.0%) and change in ITC index (27.0%) and percent IOP reductions were significantly correlated with them above (β = 0.386, β = 0.664, all P < .001) but not below the change points.

CONCLUSIONS

Quantitative assessment of circumferential ITC can predict postoperative IOP control after phacoemulsification, and thus it may be used as a reference for determining lens extraction in PACD eyes.

Classifications of Qualitative Characteristics on Angle Configurations via Ultrasound Biomicroscopy in Acute Primary Angle Closure

Purpose

To study the classifications of qualitative characteristics on the angle configurations in the acute primary angle closure (APAC) and fellow eyes by ultrasound biomicroscopy (UBM).

Methods

A total of 131 patients (262 eyes) were researched retrospectively. The qualitative parameters from UBM images were classified into iris form (IF), ciliary body configuration (CBC), basal iris thickness (BIT), iris convexity (IC), iris insert (II), iris angulation (IA), ciliary body size (CBS) and ciliary body position (CBP). Comparative analyses between the APAC (case group) and fellow (control group) eyes were performed.

Results

There were significant differences in IF, CBC, IC, II, CBS, CBP between the case group and control group in all quadrants (P<0.001). The IA of the case group and control group presented significant difference in all quadrants (P=0.001). However, there was not a significant difference in BIT between the case group and control group in all quadrants (P=0.495). The case group had fewer parallelogram-like and mushroom-like and more cone-like and hook-like CBCs than the control group (P<0.001).

Conclusion

Multiple ciliary body configurations can influence the stability of the lens and the anatomic configuration of the anterior chamber angle indirectly. New qualitative classification system of UBM may be more intuitionistic and refined to reflect the angle configurations to help clinical practice.

Evaluation of the Diagnostic Performance of Swept-Source Anterior Segment Optical Coherence Tomography in Primary Angle Closure Disease

PURPOSE

To evaluate the diagnostic performance of swept-source anterior segment optical coherence tomography (SS-OCT) in differentiating eyes with primary angle closure disease (PACD) from eyes of control subjects, as well as eyes with PAC and PAC glaucoma (PACG) from eyes with PAC suspect (PACS) disease.

DESIGN

Multicenter cross-sectional study.

METHODS

Chinese patients were classified into control, PACS, and PAC/PACG groups. The area under the receiving operating characteristic curve (AUC) from logistic regression models was used to evaluate discriminating ability. Sensitivity and specificity were calculated, and performance of the models was validated using an independent dataset.

RESULTS

A total of 2928 SS-OCT images from 366 eyes of 260 patients were recruited to develop diagnostic models. The validation dataset included 1176 SS-OCT images from 147 eyes of 143 patients. For distinguishing PACD from control eyes, average anterior chamber depth had the highest AUC (0.94). With a cutoff of 2.2 mm for average anterior chamber depth, the sensitivity and specificity were 90.2% and 85.2% in the training set. For distinguishing PAC/PACG from PACS, a multivariate model had an AUC of 0.83, with sensitivity and specificity of 82.0% and 62.8% in the training set. The validation set confirmed the findings.

CONCLUSIONS

SS-OCT of the anterior segment showed excellent diagnostic performance distinguishing PACD from normal eyes and moderate diagnostic ability distinguishing eyes with PAC/PACG from eyes with PACS. ACD alone may provide a simple and effective way to diagnose PACD from control subjects. As ACD can be obtained using other more available modalities, this has implications for the early diagnosis of PACD.

Lens-vault analysis and its correlation with other biometric parameters using swept-source OCT

PURPOSE

To measure lens vault (LV) and to assess its correlation with various ocular parameters in healthy eyes, using for all measurements the same high-resolution swept-source optical coherence tomographer (SS-OCT).

METHODS

We prospectively recruited 67 Caucasian healthy patients whose mean age was 41.9 ± 12.4 years; only their right eye was included in the study. Data were all recorded with the ANTERION SS-OCT and comprised, for each patient, 5 consecutive measurements of LV, anterior chamber depth (ACD), lens thickness (LT), axial length (AL), white-to-white (WTW) distance, central corneal thickness (CCT), anterior chamber volume (ACV) and spur-to-spur (STS) distance.

RESULTS

Mean LV was 0.26 ± 0.23 mm (ranging from -0.24 to 0.78 mm). Data analysis revealed a statistically significant negative correlation between LV and ACD (R=-0.80, p < 0.001), AL (R = -0.36, p = 0.002), and ACV (R = -0.68, p < 0.001), and a positive correlation between LV and LT (R = 0.67, p < 0.001), and age (R = 0.53, p < 0.001). In contrast, no statistically significant correlation was found between LV and WTW (R=-0.17, p = 0.15), CCT (R = 0.11, p = 0.36) or STS (R=-0.10, p = 0.41).

CONCLUSIONS

Taking into account our findings about intra-parameter correlation levels, we believe that LV should be measured and analyzed together with other ocular parameters in clinical routine practice both for diagnosis and for some refractive surgeries.

Analyzing Anatomical Factors Contributing to Angle Closure Based on Anterior Segment Optical Coherence Tomography Imaging

PURPOSE

To analyze anatomical factors contributing to angle closure based on anterior segment optical coherence tomography (AS-OCT) imaging.

METHODS

A total of 238 patients with angle closure and 1122 normal controls were consecutively recruited for this study. Participants' eyes were imaged using AS-OCT under the same darkened ambient light conditions. The following parameters were analyzed: central anterior chamber depth (ACD); anterior chamber area (ACA); anterior chamber volume (ACV), anterior chamber width (ACW); corneal diameter (CD); posterior cornea curvature (PCC); anterior cornea curvature (ACC); maximum iris thickness (ITM); iris thickness at 750 um (IT750) and 2000 um (IT2000) from the scleral spur; iris curvature (IC); iris area (IA); lens vault (LV); angle opening distance (AOD); trabecular iris space area at 500 um (TISA500) and 750 um (TISA750) from the scleral spur; angle recess area (ARA). Lasso regression models were used to detect the collinearity of parameters. The multivariable logistic regression was performed to determine the independent association between angle closure and those parameters included in Lasso regression model. Also Factor analysis was performed to extract a few underlying factors (components) from these parameters.

RESULTS

Lasso regression showed that ACD, ACV, PCC, IT750, IT2000 and LV were screened in the model. The multivariable logistic regression indicated that ACV, PCC, IT750 and LV were significantly associated with angle closure. Factor analyses revealed that 4 factors, each with its closely associated clusters of variables, produced the best results: ACA, ACV and ACD (Factor 1); LV, tIC and nIC, (Factor 2); ACW, CD and PCC (Factor 3); and tITM, tIT2000, tIT750, nIT2000 and nIT750 (Factor 4).

CONCLUSIONS

Four separate mechanisms were showed to be involved in the pathogenesis of angle closure, from anterior chamber dimensions, lens, iris and cornea respectively. The parameters ACV, PCC, IT750, and LV are more predominant in determining angle closure.

Association of peripheral anterior synechiae with anterior segment parameters in eyes with primary angle closure glaucoma

To investigate the association of peripheral anterior synechiae (PAS) with intraocular pressure (IOP) and anterior-segment parameters in subjects with primary angle-closure glaucoma (PACG). A total of 267 subjects with PACG were recruited and underwent gonioscopy and anterior-segment optical coherence tomography (ASOCT). Customized software was used to measure ASOCT parameters, including angle opening distance (AOD750) and trabecular-iris-space-area (TISA750) at 750 µm from the scleral spur, anterior chamber depth, width, area and volume (ACD, ACW, ACA, ACV), iris thickness (IT750), iris area (IAREA), and lens vault (LV). Presenting IOP was defined as the first IOP reading before the initiation of IOP-lowering treatment. The mean age of the 267 subjects was 67.0 ± 8.9 years, 140 (52.4%) were male, and 246 (92.1%) were of Chinese ethnicity. PAS was present in 122 (45.7%) subjects, and was most frequently found in the superior quadrant (79.5%). Subjects with PAS had greater presenting IOP (28.7 ± 12.9 vs 22.4 ± 9.7 mmHg, p < 0.001), narrower AOD750 (p < 0.001), smaller TISA750 (p < 0.001), ACD (p = 0.04), ACA (p = 0.02), ACV (p = 0.01) and larger LV (p = 0.01) compared to PACG eyes without PAS. No significant differences were noted for iris parameters. A multivariate logistic regression analysis showed that higher presenting IOP (β = 0.20, p < 0.001), worse visual field mean deviation (β = - 0.20, p = 0.01) and narrower AOD750 (β = - 0.25, p = 0.03) were the only parameters that significantly correlated with the extent of PAS in clock hours. Almost one-half of the subjects with PACG demonstrated PAS; these eyes were associated with higher presenting IOP, smaller anterior segment dimensions and more severe disease.

Using Anterior Segment Optical Coherence Tomography (ASOCT) Parameters to Determine Pupillary Block Versus Plateau Iris Configuration

PRéCIS:: The potential parameters for differentiating pupillary block (PB) from plateau iris configuration (PIC) on anterior segment optical coherence tomography (ASOCT) are lens/pupil size parameters and angles. Further study is needed to determine a landmark peripheral to the centroid of the iris.

PURPOSE

Investigate anterior segment parameters to distinguish between 2 mechanisms of angle closure, PB and PIC, using swept-source Fourier domain ASOCT.

PATIENTS AND METHODS

Retrospective ASOCT images from narrow angle eyes were reviewed. PIC was defined either by ultrasound biomicroscopy and/or clinically when an iridoplasty was performed. Images were read by a masked reader using Anterior Chamber Analysis and Interpretation software to identify scleral spur landmarks and calculate anterior chamber, peripheral angle, iris size, iris shape, and lens/pupil size parameters. ASOCT parameters were summarized and compared using the 2-sample t test. Thresholds and area under receiver operating characteristic curve were calculated using logistic regression analysis.

RESULTS

One hundred eyes (66 PB and 34 PIC) of 100 participants were reviewed. Of all ASOCT parameters, iris length in each quadrant, pupil arc, lens/pupil parameters (pupil arc, lens vault, and pupil diameter), all pupillary margin-center point-scleral spur landmark (PM-C-SSL) parameters, and all except superior central iris vault parameters were significantly different between PB and PIC. On threshold evaluation, lens/pupil parameters had the greatest area under receiver operating characteristic curve values (0.77 to 0.80), followed by PM-C-SSL angles (0.71 to 0.75).

CONCLUSIONS

We propose that the pupil size parameters and PM-C-SSL angle are the most reliable novel ASOCT parameters to distinguish between PB and PIC eyes. These parameters do not rely on the visibility of the posterior iris surface, which is difficult to identify with ASOCT, but may be ambient lighting dependent.

Posture-Related Changes of Intraocular Pressure in Patients With Acute Primary Angle Closure

Purpose

To evaluate the posture-related change in intraocular pressure (IOP) of eyes with angle-closure disease and the associated factors.

Methods

Eyes were prospectively enrolled and divided into three groups: eyes with acute primary angle-closure (APAC), fellow eyes of acute primary angle-closure (FAPAC), and eyes with nonacute primary angle-closure disease (PACD). All of them had been treated with laser peripheral iridotomy. IOP was measured in the sitting, supine, and lateral decubitus positions (LDP) five minutes after posture change. Anterior chamber angle parameters and angle-closure mechanism were evaluated by anterior segment optical coherence tomography.

Results

Forty-four eyes were enrolled into each group. APAC eyes showed more LDP-Sitting IOP increase than fellow eyes (5.7 ± 2.7 vs. 2.2 ± 1.4 mm Hg, P < 0.001) and nonacute PACD eyes (3.6 ± 2.0 mm Hg, P < 0.001). LDP-sitting IOP change was higher in eyes with exaggerated lens vault (having shallow anterior chamber and volcano-like iris-lens configuration) than in those without it (APAC: 6.3 ± 2.6 vs. 3.9 ± 2.1 mm Hg, P = 0.011). Linear regression revealed that LDP-sitting IOP change in the APAC group was negatively associated with angle opening distance (AOD), trabecular iris space area, scleral spur angle, and anterior chamber depth (ACD1000). With multivariable stepwise regression analysis, AOD750 remained statistically significant (beta-coefficient = −8.36, P = 0.014).

Conclusions

APAC eyes had significant posture-related IOP changes, associated with narrower angle structures and exaggerated lens vault.

Anatomic Changes and Predictors of Angle Widening after Laser Peripheral Iridotomy: The Zhongshan Angle Closure Prevention Trial

PURPOSE

To assess anatomic changes after laser peripheral iridotomy (LPI) and predictors of angle widening based on anterior segment (AS) OCT and angle opening based on gonioscopy.

DESIGN

Prospective observational study.

PARTICIPANTS

Primary angle-closure suspects (PACSs) 50 to 70 years of age.

METHODS

Participants of the Zhongshan Angle Closure Prevention (ZAP) Trial underwent gonioscopy and AS-OCT imaging at baseline and 2 weeks after LPI. Primary angle-closure suspect was defined as the inability to visualize pigmented trabecular meshwork in 2 or more quadrants on static gonioscopy. Laser peripheral iridotomy was performed on 1 eye per patient in superior (between 11 and 1 o'clock) or temporal or nasal locations (at or below 10:30 or 1:30 o'clock). Biometric parameters in horizontal and vertical AS-OCT scans were measured and averaged. Linear and logistic regression modeling were performed to determine predictors of angle widening, defined as change in mean angle opening distance measured at 750 μm from the scleral spur (AOD₇₅₀); poor angle widening, defined as the lowest quintile of change in mean AOD₇₅₀; and poor angle opening, defined as residual PACS after LPI based on gonioscopy.

MAIN OUTCOME MEASURES

Anatomic changes and predictors of angle widening and opening after LPI.

RESULTS

Four hundred fifty-four patients were included in the analysis. Two hundred nineteen underwent superior LPI and 235 underwent temporal or nasal LPI. Significant changes were found among most biometric parameters (P < 0.006) after LPI, including greater AOD₇₅₀ (P < 0.001). One hundred twenty eyes (26.4%) showed residual PACS after LPI. In multivariate regression analysis, superior LPI location (P = 0.004), smaller AOD₇₅₀ (P < 0.001), and greater iris curvature (P < 0.001), were predictive of greater angle widening. Temporal or nasal LPI locations (odds ratio [OR], 2.60, P < 0.001) was predictive of poor angle widening. Smaller mean gonioscopy grade (OR, 0.34, 1-grade increment) was predictive of poor angle opening.

CONCLUSIONS

Superior LPI location results in significantly greater angle widening compared with temporal or nasal locations in a Chinese population with PACS. This supports consideration of superior LPI locations to optimize anatomic changes after LPI.

Quantification of Iridotrabecular Contact in Primary Angle-Closure Disease

PRECIS

Iridotrabecular contact (ITC), a measure of angle closure, can be quantified along with other angle parameters on anterior segment optical coherence tomography (ASOCT). Hence, angle changes and angle closure mechanisms can be detected predicting the efficacy of iridotomy.

PURPOSE

To assess 360-degree ITC and ocular parameter changes, after laser peripheral iridotomy (LPI), in primary angle-closure disease (PACD) subgroups.

METHODOLOGY

This was a prospective observational study including 90 subjects, 30 each of primary angle-closure suspect (PACS), primary angle closure (PAC), and primary angle-closure glaucoma (PACG). Anterior segment OCT parameters were measured before and 3 weeks after LPI ITC: central anterior chamber depth, lens vault, angle-opening distance, angle recess area, trabecular iris space area, trabecular iris angle at 500 and 750 μm from scleral spur.

RESULTS

ITC was highest in PACG, 81.43%±22.39%, followed by PAC, 28.53%±21.30%, and PACS, 10.76%± 8.54% (P=0.011). There was a significant decrease in ITC in all 3 groups after iridotomy (P<0.001), with a residual ITC of 68.56%±26.44% in PACG, 18.23%±15.98% in PAC, and 5.13%±5.11% in PACS. A significant positive correlation was seen between the extent of ITC, baseline intraocular pressure, and visual field index. ITC was highest in eyes with exaggerated lens vault (77.3%±32.03%), as compared with eyes having a plateau iris configuration or relative pupillary block configuration (P<0.001).

CONCLUSIONS

Iridotomy at any stage of PACD shows a significant decrease in ITC, with areas of residual ITC. Even in PACG, the iridotomy is effective in exposing parts of the trabecular meshwork that had contact earlier. Greater baseline ITC and postlaser ITC are a biomarker for higher intraocular pressure and greater visual field damage, which need lifelong review and appropriate management.

Deep learning algorithms to isolate and quantify the structures of the anterior segment in optical coherence tomography images

BACKGROUND/AIMS

Accurate isolation and quantification of intraocular dimensions in the anterior segment (AS) of the eye using optical coherence tomography (OCT) images is important in the diagnosis and treatment of many eye diseases, especially angle-closure glaucoma.

METHOD

In this study, we developed a deep convolutional neural network (DCNN) for the localisation of the scleral spur; moreover, we introduced an information-rich segmentation approach for this localisation problem. An ensemble of DCNNs for the segmentation of AS structures (iris, corneosclera shell adn anterior chamber) was developed. Based on the results of two previous processes, an algorithm to automatically quantify clinically important measurements were created. 200 images from 58 patients (100 eyes) were used for testing.

RESULTS

With limited training data, the DCNN was able to detect the scleral spur on unseen anterior segment optical coherence tomography (ASOCT) images as accurately as an experienced ophthalmologist on the given test dataset and simultaneously isolated the AS structures with a Dice coefficient of 95.7%. We then automatically extracted eight clinically relevant ASOCT measurements and proposed an automated quality check process that asserts the reliability of these measurements. When combined with an OCT machine capable of imaging multiple radial sections, the algorithms can provide a more complete objective assessment. The total segmentation and measurement time for a single scan is less than 2 s.

CONCLUSION

This is an essential step towards providing a robust automated framework for reliable quantification of ASOCT scans, for applications in the diagnosis and management of angle-closure glaucoma.

Pseudophakic glaucoma and angle closure in a patient with an anterior chamber intraocular lens

Purpose

To report use of ultrasound biomicroscopy (UBM) and anterior segment ocular coherence tomography (AS-OCT) in a case of pseudophakic glaucoma in a patient with an anterior chamber intraocular lens.

Observations

UBM and AS-OCT were critical in determining a non-drug related etiology of angle closure. Images indicated anterior obstruction of the pupil secondary to anterior chamber intraocular lens, but also posterior obstruction of the pupil secondary to the anterior hyaloid face.

Conclusions

When evaluating a patient with suspected angle closure, it is important to perform a full ophthalmologic examination, including gonioscopy, as well as a thorough review of past medical history and medications so as not to miss systemic-related etiologies. Imaging with B-scan, UBM, and, more recently in the last decade, AS-OCT is a key component of evaluation of a patient in angle closure, especially one with a complex medical and ocular history.

Trends in the characteristics of acute primary angle closure in Korea over the past 10-years

Purpose

To investigate the changes in the demographic, clinical, and biometric characteristics of APAC patients in South Korea during the last decade.

Methods

Medical records of patients with APAC who visit the emergency department or the glaucoma clinic of Chonnam National University Hospital, a tertiary referral center in Gwangju, South Korea in 2007 and 2017 were analyzed. Demographics, clinical characteristics, and treatment modality were compared between the APAC patients in 2007 and 2017.

Results

The number of patients with APAC increased from 54 in 2007 to 68 in 2017. Female patients in their 60s were most common in both groups and there was no significant difference in IOP, cataract grade, gonioscopic grading, PAS, or optic nerve damage between the two groups at baseline visit (all P > 0.05). However, APAC eyes in 2017 had a shallower ACD (1.74 ± 0.28 mm vs 1.87 ± 0.35 mm; P = 0.024) and greater LV (1.05 ± 0.26 mm vs 0.93 ± 0.19 mm; P = 0.001) than those of APAC eyes in 2007. During one year follow-up, 25 patients (51.02%) received LPI only, and 18 patients (36.73%) required LE, and 6 patients (12.24%) required phacotrabeculectomy or sequential LE and trabeculectomy. However, in 2017, LPI alone was sufficient in 23 patients (38.33%), 29 patients (48.33%) required further LE, and 8 patients (13.33%) required phacotrabeculectomy or sequential LE and trabeculectomy for the treatment of APAC (P = 0.015).

Conclusions

Compared to older cases of APAC, recent cases received LE more frequently, which suggests an increasing trend of LE as a treatment option for APAC. In addition, recent cases had a greater LV and shallower ACD than older cases and these biometric differences may be one of the reasons for increasing rate of LE in this study.

Diurnal Variation of Optical Coherence Tomography Measurements of Static and Dynamic Anterior Segment Parameters

PURPOSE

To examine the diurnal variation of static and dynamic anterior segment parameters in young, healthy eyes by comparing anterior segment optical coherence tomography (AS-OCT) measurements obtained in the morning and evening and also in the light and dark.

METHODS

Twenty-two subjects ranging from 19 to 47 years of age with no past ocular history were selected. Imaging was performed with the Tomey CASIA2 AS-OCT device in 2 fixed lighting environments, light and dark, between the hours of 08:30 to 10:00 and 17:30 to 19:00. Four AS-OCT images were analyzed per eye. Pupil diameter (PD), iris area (IA), iris curvature (IC), anterior chamber depth (ACD), lens vault (LV), anterior chamber width (ACW), anterior chamber area (ACA), angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), and trabecular iris angle (TIA) were measured.

RESULTS

Pupil diameter was similar between the AM and PM groups in the light (P=0.89) and dark (P=0.51). There was no significant difference between AM and PM measurement values for any of the static or dynamic parameters in the light (P>0.39) and dark (P>0.31). Intraclass correlation coefficients (ICC) demonstrated excellent agreement between AM and PM measurement values in the light (ICC>0.81) and dark (ICC>0.93). In addition, there was no significant difference between AM and PM angle opening distance at 500 µm measurement values in the light (P>0.34) and dark (P>0.40) when each of 8 angle sectors was analyzed individually.

CONCLUSIONS

No significant diurnal variation of static or dynamic anterior segment parameter measurements was detected in the light and dark. Diurnal variation of these parameters does not regularly occur in young, healthy eyes.

Characteristic Manifestations regarding Ultrasound Biomicroscopy Morphological Data in the Diagnosis of Acute Angle Closure Secondary to Lens Subluxation

Purpose

To investigate the mechanisms underlying the occurrence of acute angle closure (AAC) and to further explore the sensitive indicators for clinical diagnosis of acute angle closure secondary to lens subluxation (AACSLS) through qualitative and quantitative analysis of ultrasound biomicroscopy (UBM) imaging features of eyes with AAC to provide a theoretical basis for the selection of treatment schemes.

Methods

A retrospective analysis was conducted from 2013 to 2018 on 160 eyes (160 patients) with uniocular acute angle closure crisis (AACC) complicated by cataract. The case group consisted of 29 eyes (29 patients) with lens subluxation and the control group consisted of 131 eyes (131 patients) without lens subluxation. Before the operation, computer optometry, best corrected visual acuity, intraocular pressure, slit lamp, gonioscopy, preset lens, A-mode ultrasonography, and UBM were performed. All the enrolled subjects underwent cataract surgery with or without other operations. The pupil was fully dilated, and the position of the lens was recorded before the operation. The zonular rupture and lens subluxation were further confirmed during operation. SPSS version 20.0 was used to analyze UBM imaging data from the lens subluxation group and non-lens subluxation group.

Results

The iris span (IS) value in the whole quadrant of the lens subluxation group was significantly higher than that of the non-lens subluxation group (P=0.033, 95%CI 0.01 to 0.31). The iris lens angle (ILA) in the lens subluxation group was significantly lower than that in the non-lens subluxation group in the upper, lower, nasal, temporal, and whole quadrants (P<0.001, 95%CI -8.79 to -2.78; P=0.001, 95%CI -8.36 to -2.27; P<0.001, 95%CI -9.85 to -4.98; P=0.015, 95%CI -6.67 to -0.72; P<0.001, 95%CI -8.74 to -5.83, respectively). However, the ILA of the maximum difference among the four quadrants in the lens subluxation group was significantly higher than that in the non-lens subluxation group (P<0.001, 95%CI 4.74 to 9.86). The ILA and iris lens contact distance (ILCD) showed significant negative correlations in both the lens subluxation group and non-lens subluxation group (Y=20.984-7.251X, R=0.520, and P<0.001; Y=19.923-3.491X, R=0.256, and P<0.001, respectively). The risk ratio of lens subluxation in exposed eyes with ILA=0 in one quadrant at least was significantly higher than that in nonexposed eyes without ILA=0 in all quadrants (X²=87.859, P<0.001, and odds ratio (OR)=79.200, 95% CI 23.063 to 271.983). The risk ratio of zonular rupture in exposed quadrants with ILA=0 was significantly lower than that in nonexposed eyes without ILA=0 (X²=33.884, P<0.001, OR=0.122, and 95% CI 0.053 to 0.278). The risk ratio of zonular rupture in exposed quadrants with nonforward convexity of iris was significantly lower than that in nonexposed quadrants with forward convexity of iris (X²=6.413, P=0.011, and OR=0.381; 95% CI 0.176 to 0.825).

Conclusions

ILA=0 and nonforward convexity of iris as UBM sensitive and characteristic indicators for screening lens subluxation and zonular rupture can provide new ideas and hints for clinical diagnosis of acute angle closure secondary to lens subluxation.

Differences in Anterior Chamber Angle Assessments Between Gonioscopy, EyeCam, and Anterior Segment OCT: The Chinese American Eye Study

Purpose

To quantify interquadrant differences in anterior chamber angle (ACA) configuration assessed on gonioscopy, EyeCam, and anterior segment optical coherence tomography (AS-OCT) in a cohort of Chinese Americans.

Methods

Subjects aged 50 years or older were recruited from the Chinese American Eye Study (CHES), a population-based epidemiologic study in Los Angeles, CA. Each subject underwent a complete ocular exam, including gonioscopy, EyeCam, and AS-OCT, under dark ambient lighting. Gonioscopy and AS-OCT imaging and EyeCam image grading were performed by trained ophthalmologists.

Results

Seven hundred nine eyes from 709 subjects were analyzed. Less anatomic variation among the quadrants was detected on gonioscopy and EyeCam compared with AS-OCT (P < 0.05). The mean gonioscopy grade, EyeCam grade, and AS-OCT measurement for each quadrant varied by up to 10.3%, 6.4%, and 46.2% of the superior quadrant value, respectively. There were significant interquadrant differences (P < 0.05) among mean AOD750 measurements when grouping by quadrant and gonioscopy or EyeCam grade. Mean AOD750 measurements were smallest for the superior quadrant by between 14.3% and 38.1% and 17.4% and 37.9% on gonioscopy and EyeCam, respectively, compared with other quadrants.

Conclusions

Gonioscopy and EyeCam significantly underrepresent anatomic variations of the ACA compared with AS-OCT. Gonioscopy or EyeCam grades from different quadrants do not appear to be comparable or interchangeable, which supports reconsideration of current definitions and methods used to diagnose and manage primary angle closure disease.

Translational Relevance

AS-OCT imaging raises concerns about current clinical definitions and methods that rely gonioscopy or EyeCam to assess the ACA.

Post-phacoemulsification iris changes in eyes with glaucoma or glaucoma suspect status

Purpose

This prospective study used anterior segment optical coherence tomography (AS-OCT) to determine how phacoemulsification (phaco) changes iris parameters in eyes with glaucoma or glaucoma suspect status.

Methods

Using Visante AS-OCT (Carl Zeiss Meditec AG), the following pre- and post-phaco parameters were measured: IT750 = iris thickness at 750 μm from the scleral spur; IT2000 = iris thickness 2000 μm from the scleral spur; ITCM = the maximum iris thickness at the middle one third of the iris; ICURV = iris curvature; IAREA = iris area; and pupil size = pupil diameter (mm). Only high-quality images with an identifiable scleral spur were included, and only the nasal quadrant was analyzed. A single glaucoma specialist analyzed the parameters according to the Zhongshan Angle Assessment Program (ZAAP, Guangzhou, China). Multivariate analysis was performed using mixed effects regression correcting for age, gender, and ethnicity.

Results

89 subjects and 110 eyes were included in this study. The mean age of subjects was 74.83 {+/-} 8.69 years old. Most common diagnoses were POAG and glaucoma suspect (23% and 52%, respectively), and 16% of subjects had an LPI. In multivariate analysis of AS-OCT parameters, decreases in IT750, IT2000, ITCM, ICURV, and pupil size were statistically significant (p<0.05).

Conclusions

After phacoemulsification, eyes with glaucoma as well as glaucoma suspect eyes have thinner irises and smaller pupils. This may lead to less iris-mediated aqueous outflow obstruction, providing support for early phacoemulsification glaucoma treatment.

Translational relevance

Our AS-OCT imaging findings may guide clinical practice as iris parameters become increasingly relevant in preoperative phaco planning.

Correlation between Intraocular Pressure and Angle Configuration Measured by OCT: The Chinese American Eye Study

PURPOSE

To characterize the relationship between angle configuration measured by anterior segment optical coherence tomography (AS-OCT) and intraocular pressure (IOP).

DESIGN

Cross-sectional study.

PARTICIPANTS

Subjects aged 50 years or older were identified from the Chinese American Eye Study (CHES), a population-based epidemiological study in Los Angeles, CA.

METHODS

Each subject underwent a complete ocular exam including Goldmann applanation tonometry, gonioscopy, and AS-OCT imaging. Four AS-OCT images were analyzed per eye and parameters describing angle configuration were measured, including angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), trabecular iris angle (TIA), and scleral spur angle (SSA). The relationship between AS-OCT measurements and IOP was assessed using locally-weighted scatterplot smoothing (LOWESS) regression and change-point analyses.

MAIN OUTCOME MEASURES

Correlation between AS-OCT measurements and IOP.

RESULTS

702 eyes (382 closed angle and 320 open angle) from 555 subjects were analyzed. Mean IOP for angle closure eyes was 16.3 ± 3.9 mmHg and open angle eyes was 15.3 ± 2.7 mmHg. Mean IOP increased as AS-OCT measurements decreased for all parameters except TIA750. Once measurement values dropped below parameter-specific threshold values, AS-OCT measurements and IOP were significantly correlated (p < 0.05) for AOD500 (r = -0.416), AOD750 (r = -0.213), ARA500 (r = -0.669), ARA750 (r = -0.680), TISA500 (r = -0.655), TISA750 (r = -0.641), SSA500 (r = -0.538), and SSA750 (r = -0.208). There was no correlation between AS-OCT measurements and IOP in open angle eyes (p > 0.40).

CONCLUSIONS

There is an anatomic threshold for angle configuration below which IOP is strongly related to the degree of angle closure. This finding suggests reconsideration of current definitions of angle closure and may be relevant for developing new OCT-based methods to identify patients at higher risk for elevated IOP and glaucoma.

Classification of primary angle closure spectrum with hierarchical cluster analysis

PURPOSE

To classify subjects with primary angle closure into clusters based on features from anterior segment optical coherence tomography (ASOCT) imaging and to explore how these clusters correspond to disease subtypes, including primary angle closure suspect (PACS), primary angle closure glaucoma(PACG), acute primary angle closure (APAC) and fellow eyes of APAC and reveal the factors that become more predominant in each subtype of angle closure.

METHOD

A cross-sectional study of 248 eyes of 198 subjects(88 PACS eyes, 53 PACG eyes, 54 APAC eyes and 53 fellow eyes of APAC) that underwent complete examination including gonioscopy, A-scan biometry, and ASOCT. An agglomerative hierarchical clustering method was used to classify eyes based on ASOCT parameters.

RESULTS

Statistical clustering analysis produced three clusters among which the anterior segment parameters were significantly different. Cluster 1(43 eyes) had the smallest anterior chamber depth(ACD) and area, as well as the greatest lens vault (p<0.001 for all). Cluster 2(113 eyes) had the thickest iris at 2000 microns(p = 0.048), and largest iris area(p<0.001), and the deepest ACD (p<0.001). Cluster 3(92 eyes) was characterized by elements of both clusters 1 and 2 and a higher iris curvature(p<0.001). There was a statistically significant difference in the distribution of clusters among subtypes of angle closure eyes(p<0.001). Although the patterns of clusters were similar in PACS and PACG eyes, with the majority of the eyes classified into cluster 2(55%, and 62%, respectively), the highest proportion of APAC and fellow eyes were assigned to clusters 1(44%) and 3 (51%), respectively.

CONCLUSION

Hierarchical cluster analysis identified three clusters with different features. Predominant anatomical components are different among subtypes of primary angle closure.

Differences between fellow eyes of acute and chronic primary angle closure (glaucoma): An ultrasound biomicroscopy quantitative study

PURPOSE

To compare various biometric parameters between fellow eyes of acute primary angle closure (glaucoma) [APAC(G)] and fellow eyes of chronic primary angle closure (glaucoma) [CPAC(G)].

METHODS

Ultrasound biomicroscopy examinations were performed on 47 patients with unilateral APAC(G) and 41 patients with asymmetric CPAC(G) before laser peripheral iridotomy and pilocarpine treatment. Anterior chamber depth and width (ACD and ACW), lens vault (LV), iris curvature (IC), iris root distance (IRD), trabecular-ciliary process distance (TCPD), iris-ciliary process distance (ICPD), trabecular-ciliary angle (TCA), and other biometric parameters were compared between fellow eyes of APAC(G) and fellow eyes of CAPC(G).

RESULTS

Compared with fellow eyes of CPAC(G), fellow eyes of APAC(G) had smaller ACD (P < 0.001), ACW (P = 0.007), TCPD (P = 0.016), ICPD (P = 0.008), and TCA (P = 0.006), as well as larger LV (P = 0.002), IC (P = 0.012), and IRD (P = 0.003). On multivariate logistic regression analyses, a 0.1 mm decrease in ACD (odds ratio [OR]: 0.705, 95%CI: 0.564-0.880, P = 0.002), ICPD (OR: 0.557, 95%CI: 0.335-0.925, P = 0.024), and a 0.1 mm increase in IRD (OR: 2.707, 95%CI: 1.025-7.149, P = 0.045), was significantly associated with occurrence of acute angle closures.

CONCLUSIONS

Fellow eyes of APAC(G) had smaller anterior segment dimensions, higher LV, more posterior iris insertion, greater IC, and more anteriorly rotated ciliary body compared with fellow eyes of CPAC(G). ACD, ICPD, and IRD were the three most important parameters that distinguish eyes predisposed to APAC(G) or CPAC(G).

Anterior Segment Dimensions Following Laser Iridotomy in Acute Primary Angle Closure and Fellow Eyes

PURPOSE

To compare the change in anterior segment morphology after laser peripheral iridotomy (LPI) in acute primary angle closure (APAC) and their fellow eyes.

DESIGN

Prospective, fellow eye-matched case series.

METHODS

In this study 42 individuals with unilateral episode of APAC were enrolled and the anterior segment optical coherence tomography (ASOCT) images were obtained in both eyes at baseline and at 6 weeks after LPI. A linear mixed-effects model was used to compare changes in anterior chamber and angle variables with consideration of laterality as the random effect and pupil diameter as the fixed effect.

RESULTS

APAC eyes had smaller angle parameters (P = .013 for all), less central anterior chamber depth (cACD) (P < .001), and lower anterior chamber area (ACA) (P < .001), as well as greater lens vault (LV) (P = .007), compared with fellow eyes. LPI resulted in angle widening with a significant increase in opening distance (P < .01 for all) in both APAC and fellow eyes. cACD (P = .003) and ACA (P < .001) increased and LV (P = .002) decreased in APAC eyes. However, there was no significant change in cACD (P = .190) and LV (P = .430) in fellow eyes. In both APAC eyes and fellow eyes, iris curvature decreased after LPI (P < .001). The changes in angle parameters, ACA, and iris curvature were not significantly different between the 2 groups.

CONCLUSION

In APAC eyes and their fellow eyes, LPI resulted in significant anterior chamber angle widening and increased anterior chamber area. In APAC eyes, the iris flattened, cACD deepened, and the lens shifted posteriorly after resolution of the attack. However, in fellow eyes, the increase in ACA was mainly owing to decreased iris curvature.

Associated factors of acute primary angle closure glaucoma in a sub-group of Chinese people: comparison between attack eyes and normal controls

Acute primary angle closure glaucoma (APACG) is an ophthalmic emergency that may lead to irreversible blindness. Although efforts were made to control intraocular pressure, disease progression still existed. Anterior segment optical coherence tomography (AS OCT) may provide a new insight into mechanism of APACG. In order to seek out associated factors by AS OCT, We compared anterior segment parameters between 74 APACG and 48 normal eyes. Analysis of variance, principle component analysis and logistic regression were used. APACG group had more women (75.7% vs 47.9%, p = 0.002), smaller anterior chamber (anterior chamber depth, ACD; anterior chamber area, ACA; all p = 0.001), narrower angle (AOD500, AOD750, angle opening distance at 500um and 750um; TISA500, TISA750, trabecular-iris space area at 500um and 750um; ARA500, ARA750, angle recess area at 500um and 750um; all p < 0.001), thinner iris (iris thickness at 750um, IT750; maximum of iris thickness, ITMAX; all p < 0.001), larger iris area (IA, p < 0.001) and lens vault (LV, p = 0.005). Principle component extracted were AOD500, AOD750, TISA500, TISA750, ARA500, ARA750, IA, PD (pupillary diameter), ACD, ACA and IT750. After adjusting for confounding factors, AOD750 (b = 12.40 ± 2.56, p < 0.001), IT750 (b = 10.50 ± 3.45, p = 0.002) and IA (b = −1.56 ± 0.77, p = 0.044) were significantly associated with occurrence of APACG.

Predictors of Intraocular Pressure After Phacoemulsification in Primary Open-Angle Glaucoma Eyes with Wide Versus Narrower Angles (An American Ophthalmological Society Thesis)

PURPOSE

To assess if narrower-angle status and anterior segment optical coherence tomography (AS-OCT) parameters can predict intraocular pressure (IOP) drop in primary open-angle glaucoma (POAG) patients after cataract surgery.

METHODS

This was a prospective case series of consecutive cataract surgery patients with POAG and no peripheral anterior synechiae (PAS) using a standardized postoperative management protocol. Preoperatively, patients underwent gonioscopy and AS-OCT. The same glaucoma medication regimen was resumed by 1 month. Potential predictors of IOP reduction included narrower-angle status by gonioscopy and angle-opening distance (AOD500) as well as other AS-OCT parameters. Mixed-effects regression adjusted for use of both eyes and other potential confounders.

RESULTS

We enrolled 66 eyes of 40 glaucoma patients. The IOP reduction at 1 year was 4.2±3 mm Hg (26%, P<.001) in the narrower-angle group vs 2.2±3 mm Hg (14%, P<.001) in the wide-angle group (P=.027 for difference), as classified by gonioscopy. By AOD500 classification, the narrower-angle group had 3.4±3 mm Hg (21%, P<.001) reduction vs 2.5±3 mm Hg (16%, P<.001) in the wide-angle group (P=.031 for difference). When the entire cohort was assessed, iris thickness, iris area, and lens vault were correlated with increasing IOP reduction at 1 year (P<.05 for all).

CONCLUSIONS

In POAG eyes, cataract surgery lowered IOP to a greater degree in the narrower-angle group than in the wide-angle group, and parameters relating to iris thickness and area, as well as lens vault, were correlated with IOP reduction. These findings can guide ophthalmologists in their selection of cataract surgery as a potential management option.