Anterior Chamber Angle Measurements Research Articles

Agreement and Reproducibility of Anterior Chamber Angle Measurements between CASIA2 Built-In Software and Human Graders.

This study evaluated the agreement and reproducibility of ACA measurements obtained using the built-in software of the CASIA2 (Version 3G.1) and the measurements derived from expert clinicians. Healthy volunteers underwent ophthalmological evaluation and AS-OCT examination. ACA measurements derived from automated and manual SS location were obtained using the CASIA2 automated software and clinician identification, respectively. The intraobserver, interobserver reproducibility, CASIA2-human grader reproducibility and CASIA2 repeatability were assessed using intraclass correlation coefficients (ICCs). The study examined 58 eyes of 30 participants. The CASIA2 software showed excellent repeatability for all ACA parameters (ICC > 0.84). Intraobserver, interobserver, and CASIA2-human grader reproducibility were also excellent (ICC > 0.87). Interobserver agreement was high, except for nasal TISA500, differing between observers 1 and 2 (p < 0.05). The agreement between CASIA2 measurements and human graders was high, except for nasal TISA500, where observer 1 values were smaller (p < 0.05). The CASIA2 built-in software reliably measures ACA parameters in healthy individuals, demonstrating high consistency. Although a small difference was observed in nasal TISA500 measurements, interobserver and CASIA2-human grader reproducibility remained excellent. Automated SS detection has the potential to facilitate evaluation and monitoring of primary angle closure disease.

Swept-source optical coherence tomography and ultrasound biomicroscopy study of anterior segment parameters in primary angle-closure glaucoma.

To evaluate the agreement between swept-source OCT (CASIA2) and UBM in primary angle-closure glaucoma. Eighty eyes of 40 participants diagnosed with primary angle-closure glaucoma were examined. Parameters measured included angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), trabecular iris angle (TIA), lens vault (LV), anterior chamber depth (ACD), and anterior chamber width (ACW). Angle images of nasal, temporal, superior, and inferior were acquired by the anterior segment mode of CASIA2 and UBM. One-way analysis of variance and paired t-test were used for statistical analysis, and the agreement was analyzed by internal correlation coefficient (ICC) and Bland-Altman method. One-way ANOVA pairwise comparison showed that CASIA2 or UBM had the narrowest superior chamber angle and the widest temporal chamber angle in patients with primary angle-closure glaucoma. The paired t-test showed that inter-device AOD, TIA, ARA, and TISA of superior chamber angle had significant differences (p < 0.001). There was no significant difference in the measured values of LV, ACD, and ACW (p > 0.05). The agreement of all parameters is good through the Bland-Altman method comparison. ICC result showed moderate agreement in other angle parameters except for superior ARA500 (0.739). In the anterior chamber angle measurement process, we should pay more attention to the superior chamber angle covered by eyelids. Although the agreement is acceptable between CASIA2 and UBM, the measurements could not be considered interchangeable due to the tremendous statistical difference between the two devices.

Inter-device agreement between spectral domain optical coherence tomography, ultrasound biomicroscopy, and gonioscopy in evaluating the iridocorneal angle in normotensive dogs.

There has not been a thoroughly reported study of the comparison between spectral domain-optical coherence tomography (SD-OCT) with both ultrasound biomicroscopy (UBM) and gonioscopy on the evaluation of the iridocorneal angle (ICA) in dogs. To investigate the diagnostic value of SD-OCT for the early detection of narrowing ICA by comparing and assessing inter-device agreement in anterior chamber angle (ACA) measurements obtained by SD-OCT and UBM, and ICA evaluations by gonioscopy. A total of 28 eyes from 28 client-owned dogs with normal intraocular pressure were included for examination. The ACA and angle opening distance (AOD) were measured from the SD-OCT and UBM images, and gonioscopy images were analyzed using the ICA grade and ZibWest angle index. The mean ACA and AOD for SD-OCT were 28.31° ± 5.37° and 658.42 ± 219.90 µm, and for UBM, 28.34° ± 5.82° and 859.29 ± 221.80 µm, respectively. The mean difference in ACA between the average values of SD-OCT and UBM measurements was 0.03° with a 95% limit of agreement (LoA) span of 16.2°, indicating positive agreement; that in AOD was 200.85 µm with a 95% LoA span of 1,110.95 µm, indicating poor agreement. The Pearson correlation coefficient of the ACA of SD-OCT and ZibWest indices of gonioscopy was 0.624, indicating strong agreement; that of UBM and gonioscopy was 0.43, indicating moderate agreement. SD-OCT is well tolerated by canine patients due to its non-contact method and might be an alternative option for early screening of ICA narrowing in clinical settings.

Relationship between anterior chamber angle, IOP, corneal curvature and refractive status in young Caucasian adults

AbstractPurpose: To investigate the relationship between anterior chamber angle (ACA) measurement, intraocular pressure (IOP) and refractive status of the eye in a young adult population with good ocular health.Methods: Autorefractor (AR) captured data on corneal curvature and refractive errors in group participants and enabled comparison across refractive groups, gender, and age. Refractive errors were calculated in diopters as the spherical equivalent (SE). IOP was taken by Pulsar non-contact tonometer. All patients underwent the same optometric examinations of anterior eye data on corneal curvature, anterior chamber angle and corneal thickness captured with Topcon Maestro optical coherence tomography (OCT). Slit lamp was used for Van Herick method.Results: Measurements were obtained from 118 eyes (right), of 26 males and 92 females aged 19–40 years with no ocular disease. There was no significant change Relationship between anterior chamber angle, IOP, corneal curvature and refractive status in young Caucasian adults in ocular profile across age range or by sex, apart from slightly steeper corneal profile for females (p=0.03). There was no significant correlation between IOP and ACA (p&amp;gt; 0.05), nor IOP and SE (p&amp;gt;0.05); however, when those with hyperopic SE were examined separately, there was a significant decrease in IOP with higher levels of hyperopic SE (p &amp;lt;0.05).Conclusion: This study reports mean values for ACA were 39,39°, which gives a value of the open anterior chamber angle in young Caucasian adults. There was no significant relation between IOP, ACA or SE in the sample of young adults. However, higher level of hyperopic SE has a significant decrease in IOP and should be further investigated due to small sample of hyperopic subjects.

Reproducibility of deep learning based scleral spur localisation and anterior chamber angle measurements from anterior segment optical coherence tomography images

AimsTo apply a deep learning model for automatic localisation of the scleral spur (SS) in anterior segment optical coherence tomography (AS-OCT) images and compare the reproducibility of anterior chamber angle...

Distribution of anterior chamber angle measurements in South African young adults: an optical coherence tomography study

Assessment of anterior chamber angle (ACA) variables is important to screen, diagnose and monitor ocular anomalies. Even though data on ACA variables, such as angle-opening distance taken at 500µm (AOD500) and trabecular-iris angle (TIA), are available in the literature, limited information is available about these variables in African sub-populations. The purpose of this study is to describe the distribution of ACA measurements (AOD500 and TIA) in a South African young adult population. In this cross-sectional study, 700 young adults were recruited from a university student population using two-stage random sampling. The Optovue iVue 100 optical coherence tomographer was used to measure the ACA variables. The distribution of the AOD500 and TIA measurements was analysed using descriptive and inferential statistics. Data from only the right eyes were analysed because the ACA measurements in the two eyes showed high levels of interocular symmetry. The measurements for the nasal and temporal ACAs were asymmetrically distributed (p < 0.001). The median AOD500 measurements in the nasal and temporal angles were 539µm and 542µm, respectively. The median TIA measurements were similar (~ 36°) in the two horizontal angles. The temporal ACA measurements were slightly higher than the nasal ACA measurements. Females had higher median ACA measurements than males (p ≥ 0.029). The ACA measurements in South African young adults resemble non-Gaussian curves. The ACA measurements are different from that reported in other sub-populations worldwide and most participants had ACA measurements associated with non-occludable ACAs.

Assessment of a Vision-Based Technique for an Automatic Van Herick Measurement System

The adoption of Artificial Intelligence methods within the instrumentation and measurements field is nowadays an attractive research area. On the one hand, making machines learn from data how to perform an activity, rather than hard code sequential instructions, is a convenient and effective solution in many modern research areas. On the other hand, AI allows for the compensation of inaccurate or not complete models of specific phenomena or systems. In this context, this paper investigates the possibility to exploit suitable Machine Learning techniques in a vision-based ophthalmic instrument to perform automatic Anterior Chamber Angle (ACA) measurements. In particular, two CNN&#x2013;based networks have been identified to automatically classify acquired images and select the ones suitable for the Van&#x2013;Herick procedure. Extensive clinical trials have been conducted by clinicians, from which a realistic and heterogeneous image dataset has been collected. The measurement accuracy of the proposed instrument is derived by extracting measures from the images of the aforementioned dataset, as well as the system performances have been assessed with respect to differences in patients&#x2019; eye color. Currently, the ACA measurement procedure is performed manually by appropriately trained medical personnel. For this reason, Machine Learning and Vision&#x2013;Based techniques may greatly improve both test objectiveness and diagnostic accessibility, by enabling an automatic measurement procedure.

Comparison of anterior chamber angle parameters and iris structure of juvenile open-angle glaucoma and pigmentary glaucoma.

Purpose:To compare the quantitative measurements of the anterior chamber angle (ACA) and iris parameters in patients with juvenile open-angle glaucoma (JOAG), pigmentary glaucoma (PG), and healthy controls using anterior segment optical coherence tomography (AS-OCT).Methods:This was a retrospective, cross-sectional study of 25 eyes with JOAG, 25 eyes with PG, and 25 control eyes. Anterior chamber depth, angle-opening distance 500 and 750, trabecular–iris space 500 and 750, scleral spur angle, iris thickness (IT, measured at the thickest part), and iris bowing were obtained using AS-OCT (Visante” OCT 3.0 Model 1000, Carl Zeiss Meditec, Inc).Results:The quantitative ACA parameters were found to be significantly higher in JOAG and PG patients compared to healthy controls (P < 0.001); there was no significant difference between the eyes with JOAG and PG (P > 0.05). In eyes with JOAG and PG, there was significantly backward bowing of the iris in temporal and nasal angles compared to control subjects (P < 0.001). Median iris bowing was not significantly different between the patients with JOAG and PG (P > 0.05). The temporal and nasal angle iris thickness were significantly thinner in eyes with JOAG than the eyes with PG (P < 0.001) and age-matched control subjects (P < 0.001). The median IT did not differ between the patients with PG and control subjects (P > 0.05). In patients with JOAG, the intraocular pressure (IOP) was inversely correlated with IT (r = -0.43, P < 0.05).Conclusion:AS-OCT provided quantitative data on the ACA and iris parameters in JOAG and PG. The evaluation of the ACA and iris structures using AS-OCT revealed higher ACA measurements and posterior bowing of the iris in patients with JOAG and PG. Furthermore, the patients with JOAG were found to have thinner IT than the ones with PG and healthy controls.

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

ABSTRACT 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.

The effects of cyclopentolate 1% versus tropicamide 1% on anterior segment angle parameters in three refractive pediatric groups.

This study aims to assess the effects of topical tropicamide 1% versus cyclopentolate hydrochloride 1% on the main numerical anterior chamber angle parameters using anterior segment optical coherence tomography (AS-OCT) in myopic, emmetropic, and hyperopic pediatric populations. One hundred eight healthy and non-amblyopic children were enrolled in this prospective study. The children were assigned into three refractive groups of myopia, emmetropia, and hyperopia for both tropicamide and cyclopentolate administrations. Half of the children in three groups were instilled tropicamide 1%, and the remaining halves were instilled cyclopentolate hydrochloride 1%. AS-OCT measurements of the anterior chamber angle in three groups were performed at the temporal areas of the right eyes under similar conditions at baseline, 30min after tropicamide, and 45min after cyclopentolate instillations. Main measurements including the angle-opening distance at 500µm anterior to the scleral spur (AOD500), trabecular iris space area at 500µm anterior to the scleral spur (TISA500), and scleral spur angle (SSA) were compared between three refractive groups. The groups were age and gender-matched. The mean baseline spherical equivalents were similar in hyperopia groups of the tropicamide (+2.34 ± 0.44) and cyclopentolate (+2.18 ± 0.32) administrations (p = 0.284), as well as the myopic children administered with tropicamide (-2.68 ± 0.40) and cyclopentolate (-2.74 ± 0.38), (p = 0.406). All baseline measurements of AOD500, TISA500, and SSA measurements were similar in three refractive groups for both tropicamide and cyclopentolate as well as the final measurements and thus measurement changes between two sessions (P >0.05 for all). Both drops induced an increase of AOD500, TISA500, and SSA measurements in three refractive groups (p <0.05 for all). Cycloplegic effects of topical instillations of tropicamide and cyclopentolate lead to a significant increase in anterior chamber angle measurements of AS-OCT. This similar effect of the drops should be considered for proper clinical assessment in children.

An insight into Principle and Practice of Anterior Segment Optical Coherence Tomography

Proper visualization of the eye structures is the hallmark of diagnosis in eye diseases. With advent of newer techniques and instruments, the significance of anterior segment eye structures is further elaborated. This article explores the basic working principle of optical coherence tomography (OCT) and also provides a list of commonly available instruments and their advantages over one another. It then sheds light upon the use of anterior segment OCT in the observation of cornea, conjunctiva, lacrimal gland and other anatomic structures of eye within the living subject. Anterior segment OCT is also helpful in the demonstration of dynamics involving aqueous flow system. The application of this advanced technique in diagnosis of dry eye disease, keratoconus, anterior segment eye tumors and other diseases is also explained. The examination of normal cornea along with all its layers is possible with anterior segment OCT and it can also point out any abnormality in corneal epithelium, edema or any other change that may occur after intra ocular lens placement or corneal transplantation. Anterior chamber angle measurement is an essential step in the diagnosis of angle closure glaucoma and quite accurate results are provided by this technique. The data was searched from PubMed and Google Scholar, from the articles published during 2014 and 2020, using the keywords “optical coherence tomography”, “glaucoma” and “anterior segment of eye”. A few of the limitations of OCT are also discussed along with the future perspectives of this powerful instrument. Keywords: Anterior Eye Segment; Optical Coherence Tomography; Glaucoma; Anterior Chamber Angle.

Iridocorneal Angle Assessment After Laser Iridotomy With Swept-source Optical Coherence Tomography

To investigate the reliability of anterior chamber angle (ACA) measurements in narrow angles and assess the effect of laser peripheral iridotomy (LPI) on these measurements using novel swept-source optical coherence tomography (SS-OCT) technology. In this prospective observational study, patients with gonioscopically narrow angles were enrolled and scheduled for prophylactic LPI. Twelve ACA sections were obtained in each eye using SS-OCT (ANTERION, Heidelberg Engineering, Germany) before and after Nd:YAG LPI. A built-in algorithm calculated ACA measurements after manual identification of the scleral spur and ACA recess. Eight ACA parameters were evaluated: ACA (ACA 500, ACA 750); scleral spur angle (SSA 500, SSA 750); angle opening distance (AOD 500, AOD 750); and trabecular iris space area (TISA 500, TISA 750). The effect of LPI was assessed for each parameter, both nasally and temporally. Ten patients (18 eyes) were enrolled (mean age, 61.8±13.6 y; 60.0% female individuals). On average, the ACA was wider nasally than temporally (P=0.004). LPI significantly widened the ACA (range, 26.7-29.4%; P<0.05). ACA 500 increased by 29.4% (P<0.001), ACA 750 by 29.2% (P=0.002), SSA 500 by 27.3% (P=0.003), SSA 750 by 28.1% (P=0.001), AOD 500 by 28.6% (P=0.009), AOD 750 by 28.6% (P=0.003), TISA 500 by 27.3% (P=0.004), and TISA 750 by 26.7% (P=0.200). SS-OCT ANTERION imaging can be used to reliably measure ACA before and after LPI. ACA, AOD, SSA, and TISA are all valid ACA measurement methods.

Automatic Anterior Chamber Angle Measurement for Ultrasound Biomicroscopy Using Deep Learning.

To develop a software package for automated measuring of the trabecular-iris angle (TIA) using ultrasound biomicroscopy. Ultrasound biomicroscopy images were collected and the TIA was manually measured by specialists. Different models were used as the convolutional neural network for the automatic TIA measurement. The root-mean-squared error, explained variance, and mean absolute percentage error were used to evaluate the performance of these models. The interobserver reproducibility, coefficient of variation, and intraclass correlation coefficient were calculated to evaluate the consistency between the manual measured and the model predicted values. ResNet-18 had the best performance in root-mean-squared error, explained variance, and mean absolute percentage error among all 5 models. The average difference between the angles measured manually and by the model is -0.46±3.97 degrees for all eyes, -1.67±5.19 degrees for open angles, and 0.75±1.43 degrees for narrow angles. The coefficient of variation, intraclass correlation coefficient, and reproducibility of the total TIA measurements are 6.8%, 0.95, and 6.1 degrees for all angles; 6.4%, 0.99, and 7.7 degrees for open angles; and 8.8%, 0.93, and 4 degrees for narrow angles, respectively. Preliminary results show that this fully automated anterior chamber angle measurement method can achieve high accuracy and have good consistency with the manual measurement results, this has great significance for future clinical practice.

Effect of Hemodialysis on Anterior Chamber Angle Measured by Anterior Segment Optical Coherence Tomography.

Purpose To investigate the effect of hemodialysis (HD) on the anterior chamber angle by anterior segment optical coherence tomography (ASOCT) and other ophthalmologic parameters in patients with end-stage kidney disease (ESKD). Methods A prospective observational study was performed on 20 patients who underwent HD for ESKD. Anterior chamber angle images were obtained by 16 mm line scan of ASOCT. The angle opening distance (AOD) and the trabecular-iris space area (TISA) were determined using the ImageJ program. Additional 12 mm horizontal and 9 mm vertical wide-field scans centered on the posterior pole were performed for the measurement of peripapillary retinal nerve fiber layer (pRNFL) thickness and macular ganglion cell-inner plexiform layer (mGCIPL) thickness. Changes in intraocular pressure (IOP), AOD, TISA, pRNFL thickness, and mGCIPL thickness before and after HD were statistically analyzed. Results The IOP decreased significantly from 17.5 ± 3.4 before HD to 16.2 ± 2.3 after HD (P=0.017). There was a statistically significant decrease in AOD 750 and TISA 750 (P=0.005 and P=0.007, respectively). AOD 500 and TISA 500 also decreased, which was almost statistically significant (P=0.061 and P=0.081, respectively). Mean pRNFL thickness and mGCIPL thickness did not show significant change after HD. Conclusion We observed a significant decrease in IOP and anterior chamber angle measurements after HD. Our study suggests that HD can influence the anterior segment structure of eyes.

Comparison of spectral domain and swept source optical coherence tomography for angle assessment of Chinese elderly subjects

BackgroundThis comparative study aimed to demonstrate the differences between swept source OCT (SS-OCT) (1310 nm) and spectral domain OCT (SD-OCT) (840 nm) for the identification and measurement of anterior chamber angle (ACA) structures.MethodsSixty seven eyes from 67 healthy subjects underwent ACA imaging at the nasal and temporal sides using SS-OCT and SD-OCT with different wavelength (Tomey, 1310 nm and RTvue, 840 nm). Images were evaluated for the ability to distinguish angle structures including the Schwalbe’s line (SL), the Schlemm’s canal (SC) and the scleral spur (SS). The length of trabecular meshwork (LTM), the angle-opening distance (AOD500 and AOD750) and the length of Schlemm’s canal (LSC) were also measured.ResultsThe nasal identification rate for SL, SC and SS were 91.04%/89.55%, 50.75%/40.30% and 100.0%/74.63% (SS-OCT/SD-OCT), respectively. The temporal identification rate for SL, SC and SS were 86.57%/91.04%, 68.66%/70.15% and 100.0%/65.67% (SS-OCT/SD-OCT), respectively. Differences between SS-OCT and SD-OCT were found in terms of the visualization of the SS. With respect to the measurements of angle, the evaluation of LTM at the nasal side, LSC at the temporal side and AOD500/750 at both sides showed significant difference between the two devices. However, there existed good correlation between the AOD500/750 measured by SS-OCT and SD-OCT (Spearman’s rank correlation coefficient > 0.8, p < 0.000).ConclusionsSS-OCT displayed a better performance in detecting deeper structures of the angle such as the SS. However, for discriminating structures lying in transparent or semi-transparent tissue such as the SL and the SC, the two devices showed good consistency. Although SS-OCT and SD-OCT demonstrated high correlation for angle measurement (AOD500/750), their agreement was poor.

Identification of eyes at risk of acute primary angle-closure in elderly Japanese patients.

Purpose: To identify from the anterior segment the structural variables of the eyes that can be used to distinguish acute primary angle-closure (APAC) eyes or primary angle-closure suspect (PACS) eyes from normal eyes.Patients and methods: We used a Pentacam scanner to measure participants’ anterior eye segments. We assessed each anterior segment structure variable on the basis of receiver operating characteristic curves using the area under the curve (AUC).Results: AUCs for eyes in men with APAC were 1.000 for central anterior chamber depth (ACD), 0.982 for peripheral ACD, 0.916 for anterior chamber angle (ACA), and 0.992 for anterior chamber volume (ACV). AUCs for eyes in women with APAC were 0.997 for central ACD, 0.942 for peripheral ACD, 0.922 for ACA, and 0.946 for ACV. AUCs for eyes in men with PACS were 0.933 for central ACD, 0.930 for peripheral ACD, 0.887 for ACA, and 0.937 for ACV. AUCs for eyes in women with PACS were 0.960 for central ACD, 0.957 for peripheral ACD, 0.937 for ACA, and 0.937 for ACV. The negative predictive values (%) in men with APAC were 100 for all the four variables (central ACD, peripheral ACD, ACA, and ACV). The negative predictive values (%) in women with APAC were 100 for central ACD, 98.7 for peripheral ACD, 97.1 for ACA, and 97.9 for ACV. The negative predictive values (%) in men with PACS were 98.6 for central ACD, 100 for peripheral ACD, 98.5 for ACA, and 99.4 for ACV. The negative predictive values (%) in women with PACS were 100 for central ACD, 98.7 for peripheral ACD, 97.1 for ACA, and 97.9 for ACV.Conclusions: The central ACD, peripheral ACD, ACA, and ACV measurements seem to be excellent markers to identify eyes without APAC or PACS.

Assessment of angle of anterior chamber with SD-OCT in patients presenting to tertiary health care center

Assessment of angle of anterior chamber with SD-OCT in patients presenting to tertiary health care center - IJCEO- Print ISSN No: - 2395-1443 Online ISSN No:- 2395-1451 Article DOI No:- 10.18231/2395-1451.2019.0016, Indian Journal of Clinical and Experimental Ophthalmology-Indian J Clin Exp Ophthalmol

Identification and Characterization of Imaging Technique Errors and Artifacts Using Anterior-Segment OCT for Irido-Corneal Angle Evaluations in Glaucoma

Anterior-segment OCT (AS-OCT) platforms provide noninvasive and quantifiable evaluations of anterior chamber angle (ACA) anatomy. Although these ACA measurements have been validated with high repeatability and reproducibility, there is a paucity of data previously published regarding the technique errors and artifacts (TEA) that may occur during imaging of the ACA. The purpose of this study was to report on the types and frequency of imaging TEA that are seen in ACA evaluation of a large cohort of patients with open-angle glaucoma. Retrospective, cross-sectional design. Images were obtained with AS-OCT from 5082 eyes of 2541 patients with glaucoma and were reviewed at the Doheny Image Reading Center (DIRC). Images had been captured using AS-OCT devices from 4 different manufacturers (Zeiss Cirrus [Oberkochen, Germany], Heidelberg Spectralis [Heidelberg, Germany], Optovue RTVue [Fremont, CA], or Zeiss Visante). All images were analyzed by 2 independent and certified DIRC image readers for angle opening distance under Schwalbe's line (SL-AOD), and then re-reviewed by a DIRC-certified principal investigator to adjudicate nonconsensus measurements. Images were defined to have TEA when image readers were unable to confidently measure the SL-AOD. Type and frequency of TEA in the AS-OCT image. Of 5082 eyes reviewed, 208 images (4.09%) were found to have TEA that restricted proper visualization of irido-corneal angle structures and measurements of SL-AOD. The most common TEA was that the image readers were unable to identify Schwalbe's line (74% of TEA images). Other common TEA included poor visualization of the anterior iris surface (15%), misaligned scan location (11%), irregular corneal irregularities (5%), and illumination-related pupillary abnormalities (4%). This large-scale study presents the types and frequency of TEA found in AS-OCT-derived angle images. More than 95% of the images reviewed were usable for the quantification of irido-corneal angle measurements. Knowing the common types of TEA may help in enhancing the training of both human image readers and in the design of automated algorithms to improve image acquisition and image interpretation parameters. This will become especially useful as AS-OCT becomes more widely used in clinical practice for anterior chamber assessment.

Predicting the outcome of laser peripheral iridotomy for primary angle closure suspect eyes using anterior segment optical coherence tomography

Develop an algorithm to predict the success of laser peripheral iridotomy (LPI) in primary angle closure suspect (PACS), using pretreatment anterior segment optical coherence tomography (ASOCT) scans. A total of 69 eyes with PACS underwent LPI and time-domain ASOCT scans (temporal and nasal cuts) were performed before and after LPI. After LPI, success is defined as one or more angles changed from closed to open. All the pretreatment ASOCT scans were analysed using the Anterior Segment Analysis Program to derive anterior chamber angle (ACA) measurements. The measurements for each angle were ordered along with angle-independent measurements totalling to 42 measurements which serve as features for the prediction algorithm. Two masked glaucoma fellowship-trained ophthalmologists graded the pre-LPI ASOCT scans to determine whether LPI was likely to successful. There were 42 (60.9%) eyes that fulfilled the criteria for success after LPI. Iris concavity, angle recess area (750μm) and iris concavity ratio showed the highest predictive score and were selected using correlation-based subset selection method. These features were classified into two ('successful' and 'unsuccessful') categories using a Bayes classifier. The algorithm predicted the success of LPI with 79.28% cross validation accuracy, which was superior to the predictive accuracy of the ophthalmologists (kappa 0.497 and 0.636 respectively). Using pretreatment ASOCT scans, our algorithm was superior to ophthalmologists in predicting the success of LPI for PACS eyes. This novel algorithm could aid decision making in offering LPI as a prophylaxis for PACS.

How Does Usage of Serotonin Noradrenaline Reuptake Inhibitors Affect Intraocular Pressure in Depression Patients?

To evaluate anterior segment parameters and intraocular pressure (IOP) modifications in patients using serotonin noradrenaline reuptake inhibitors (SNRIs) due to major depressive disorder. This cross-sectional study included 170 eyes of 85 subjects. All subjects were divided into three groups: group 1 included 44 healthy control subjects, group 2 included 22 patients receiving antidepressants for 1 week to 6 months, and group 3 included 19 patients receiving antidepressants for >6 months. All subjects underwent a detailed ophthalmologic examination, including gonioscopy. Anterior segments of all subjects were evaluated with the Scheimpflug system and pupil diameter (PD), central corneal thickness, anterior chamber depth (ACD), anterior chamber volume, and anterior chamber angle (ACA) measurements were enrolled. The median IOP was significantly lower in patients using antidepressants [16.0 (11.0-21.0) mmHg] than the control group [17.5 (12.0-21.0) mmHg] (P = 0.041). The PD was significantly larger in patients using antidepressants [3.56 (2.29-5.60) mm] than the control group [2.95 (2.00-4.40) mm] (P = 0.000). In the study group, PD was also significantly larger in patients using SNRIs for ≥6 months [3.67 (2.38-5.08) mm] than <6 months [3.31 (2.29-5.60) mm] (P = 0.000). The median ACD was significantly lower in patients using antidepressants for ≥6 months [3.21 (2.52-4.06) mm] than the control group [3.44 (2.63-4.29) mm] (P = 0.000). ACAs were measured between 25° and 55° by Scheimpflug imaging. Treatment of SNRIs causes mydriasis and decrease in width of ACD. These changes may not increase IOP as long as the patient has an open angle. SNRIs lead to decrease in IOP particularly in long-term usage.