Predictive Value of the Water Drinking Test and the Risk of Glaucomatous Visual Field Progression.

PURPOSE: The purpose of this is to test the hypothesis the intraocular pressure (IOP) peaks during a stress test [the water drinking test (WDT)] can estimate the risk of future visual field progression in treated primary open-angle glaucoma (POAG) patients. PATIENTS AND METHODS: Design: Prospective, longitudinal study. SETTING: Clinical practice. STUDY POPULATION: Treated POAG patients whose IOP was ≤18 mm Hg and who had no IOP-lowering interventions between the date of the WDT and the last eligible visual field. INTERVENTION: At baseline examination, patients underwent the WDT and were then followed at regular intervals with office-based IOP measurements and visual field testing. MAIN OUTCOME MEASURE: Cox-proportional hazards survival analysis testing the predictive value of IOP peaks during the WDT versus IOP measurements during office hours on visual field progression. RESULTS: A total of 144 eyes of 96 patients with baseline visual field damage ranging from mild to severe followed for a mean of 28 months were analyzed. In the multivariable analysis adjusting for potential confounders, higher IOP peaks during the WDT were predictive of future visual field progression (hazard ratio=1.11; 95% confidence interval, 1.02 to 1.21; P=0.013). The average and peak IOP during office hours over the same follow-up period were not significantly associated with progression (P=0.651 and 0.569, respectively). CONCLUSIONS: IOP peaks detected with the WDT were predictive of future visual field progression in a treated POAG population. This stress test could be a useful tool for risk assessment in daily practice.

Association of Baseline Anterior Segment Parameters With the Development of Incident Gonioscopic Angle Closure.

IMPORTANCE: Baseline anterior segment imaging parameters associated with incident gonioscopic angle closure, to our knowledge, are unknown. OBJECTIVE: To identify baseline quantitative anterior segment optical coherence tomography parameters associated with the development of incident gonioscopic angle closure after 4 years among participants with gonioscopically open angles at baseline. DESIGN, SETTING, AND PARTICIPANTS: Three hundred forty-two participants aged 50 years or older were recruited to participate in this prospective, community-based observational study. Participants underwent gonioscopy and anterior segment optical coherence tomography imaging at baseline and after 4 years. Custom image analysis software was used to quantify anterior chamber parameters from anterior segment optical coherence tomography images. MAIN OUTCOMES AND MEASURES: Baseline anterior segment optical coherence tomography measurements among participants with gonioscopically open vs closed angles at follow-up. RESULTS: Of the 342 participants, 187 (55%) were women and 297 (87%) were Chinese. The response rate was 62.4%. Forty-nine participants (14.3%) developed gonioscopic angle closure after 4 years. The mean age (SD) at baseline of the 49 participants was 62.9 (8.0) years, 15 (30.6%) were men, and 43 (87.8%) were Chinese. These participants had a smaller baseline angle opening distance at 750 µm (AOD750) (0.15 mm; 95% CI, 0.12-0.18), trabecular iris surface area at 750 µm (0.07 mm2; 95% CI, 0.05-0.08), anterior chamber area (30 mm2; 95% CI, 2.27-3.74), and anterior chamber volume (24.32 mm2; 95% CI, 18.20-30.44) (all P < .001). Baseline iris curvature (-0.08; 95% CI, -0.12 to -0.04) and lens vault (LV) measurements (-0.29 mm; 95% CI, -0.37 to -0.21) were larger among these participants ( all P < .001). A model consisting of the LV and AOD750 measurements explained 38% of the variance in gonioscopic angle closure occurring at 4 years, with LV accounting for 28% of this variance. For every 0.1 mm increase in LV and 0.1 mm decrease in AOD750, the odds of developing gonioscopic angle closure was 1.29 (95% CI, 1.07-1.57) and 3.27 (95% CI, 1.87-5.69), respectively. In terms of per SD change in LV and AOD750, this translates to an odds ratio of 2.14 (95% CI, 2.48-12.34) and 5.53 (95% CI, 1.22-3.77), respectively. A baseline LV cut-off value of >0.56 mm had 64.6% sensitivity and 84.0% specificity for identifying participants who developed angle closure. CONCLUSIONS AND RELEVANCE: These findings suggest that smaller AOD750 and larger LV measurements are associated with the development of incident gonioscopic angle closure after 4 years among participants with gonioscopically open angles at baseline.

Comparison of the Intraocular Pressure Variation Provoked by Postural Change and by the Water Drinking Test in Primary Open-angle Glaucoma and Normal Patients.

PURPOSE: To evaluate the intraocular pressure (IOP) peak and variability detected by moving the body from sitting to supine position (postural test) and by the water drinking test (WDT) in normal and primary open-angle glaucoma (POAG) subjects. PATIENTS AND METHODS: Prospective, cross-sectional observational analysis of 14 eyes of 14 normal subjects and 31 eyes of 31 patients with POAG. All POAG subjects were under clinical therapy. IOP measurements were all performed on the same day. RESULTS: When the subjects moved to the supine position, there was an IOP increase of 1.36±1.34 and 2.84±2.21 mm Hg in the normal and POAG groups, respectively (P=0.011). During the WDT, mean IOP peak and fluctuation in the POAG group was 19.29±4.10 and 4.13±2.33 mm Hg, respectively. These levels were significantly higher in comparison with the normal group (16.50±3.76 and 2.71±0.99 mm Hg; P=0.018 and 0.022, respectively). The mean peak IOP observed in the WDT was significantly higher than the IOP in the supine position (19.29±4.10 vs. 17.32±4.66 mm Hg, P=0.013). The mean IOP increase during the WDT was also significantly higher when compared with the postural test (4.13±2.33 vs. 2.84±2.21 mm Hg, P=0.019). CONCLUSIONS: POAG eyes demonstrated a significant IOP increase when assuming the supine position and during the WDT. The IOP increase during the WDT was significantly higher than the IOP increase after postural test. Hence, the results of both tests are not interchangeable.

Anterior Segment Imaging Predicts Incident Gonioscopic Angle Closure.

PURPOSE: To investigate the incidence of gonioscopic angle closure after 4 years in subjects with gonioscopically open angles but varying degrees of angle closure detected on anterior segment optical coherence tomography (AS OCT; Visante; Carl Zeiss Meditec, Dublin, CA) at baseline. DESIGN: Prospective, observational study. PARTICIPANTS: Three hundred forty-two subjects, mostly Chinese, 50 years of age or older, were recruited, of whom 65 were controls with open angles on gonioscopy and AS OCT at baseline, and 277 were cases with baseline open angles on gonioscopy but closed angles (1-4 quadrants) on AS OCT scans. METHODS: All subjects underwent gonioscopy and AS OCT at baseline (horizontal and vertical single scans) and after 4 years. The examiner performing gonioscopy was masked to the baseline and AS OCT data. Angle closure in a quadrant was defined as nonvisibility of the posterior trabecular meshwork by gonioscopy and visible iridotrabecular contact beyond the scleral spur in AS OCT scans. MAIN OUTCOME MEASURES: Gonioscopic angle closure in 2 or 3 quadrants after 4 years. RESULTS: There were no statistically significant differences in age, ethnicity, or gender between cases and controls. None of the control subjects demonstrated gonioscopic angle closure after 4 years. Forty-eight of the 277 subjects (17.3%; 95% confidence interval [CI], 12.8-23; P < 0.0001) with at least 1 quadrant of angle closure on AS OCT at baseline demonstrated gonioscopic angle closure in 2 or more quadrants, whereas 28 subjects (10.1%; 95% CI, 6.7-14.6; P < 0.004) demonstrated gonioscopic angle closure in 3 or more quadrants after 4 years. Individuals with more quadrants of angle closure on baseline AS OCT scans had a greater likelihood of gonioscopic angle closure developing after 4 years (P < 0.0001, chi-square test for trend for both definitions of angle closure). CONCLUSIONS: Anterior segment OCT imaging at baseline predicts incident gonioscopic angle closure after 4 years among subjects who have gonioscopically open angles and iridotrabecular contact on AS OCT at baseline.

Changes in anterior segment dimensions over 4†years in a cohort of Singaporean subjects with open angles.

AIM: To evaluate quantitative changes in anterior segment optical coherence tomography (AS-OCT) parameters at 4 years in subjects with open angles on gonioscopy at baseline. METHODS: 339 gonioscopically open-angle subjects aged >50 years underwent AS-OCT imaging (Visante, Carl Zeiss Meditec, Dublin, California, USA) at baseline and at 4 years. Customised software was used to analyse images. Linear regression was performed to assess baseline predictors of change in mean trabecular iris space area (TISA). RESULTS: Of the 339 subjects, 204 (61%) had good images for analysis. The mean age at baseline was 60 (SD 6.42) years; 55.4% were women and 87.7% were Chinese. Overall, there was a decrease in anterior chamber depth (ACD), anterior chamber area (ACA), anterior chamber volume (ACV) and angle opening distance at 500/750 µm, TISA 500/750 µm, iris thickness at 2000 µm and iris area in both nasal and temporal quadrants (p<0.05) at 4 years. There was an increase in iris curvature (ICURV) and lens vault (LV) (p<0.05). With univariate analysis, shorter axial length (AxL), shallower ACD, greater LV, smaller ACA/ACV and larger mean ICURV at baseline were associated with less change in TISA750 at follow-up. On multivariate analysis, only baseline mean ICURV and shorter AxL were predictive of less change in TISA750 at 4 years. CONCLUSIONS: Angle width significantly decreased; ICURV and LV increased in subjects with gonioscopically open angles followed at 4 years. Eyes with shorter AxL and greater ICURV at baseline had lesser decrease in angle width.

Sectoral variations of iridocorneal angle width and iris volume in Chinese Singaporeans: a swept-source optical coherence tomography study.

PURPOSE: To assess variations in the iridocorneal angle width and iris volume in Chinese subjects using swept-source optical coherence tomography (SS-OCT). METHODS: Consecutive subjects, aged 40-80 years, with no previous ophthalmic problems were recruited from a population-based study of Chinese Singaporeans. All subjects underwent 360° SS-OCT (SS-1000 CASIA, Tomey Corporation, Nagoya, Japan) angle imaging and gonioscopy in one randomly selected eye in the dark. For each eye, 16 frames (11.25° apart) were selected for analysis from 128 cross-sectional images, and measurements of the trabecular iris space area 750 µm from the scleral spur (TISA750) and iris volume were made for each image. The measurements from four consecutive frames were further averaged as a sector of 45°. Sector-wise angle width and quadrant-wise iris volume were analyzed. RESULTS: Two hundred and twelve subjects (90 with closed-angles) were examined. The majority of the subjects were female (70.7 %) with mean age 61 (±8.9) years. The TISA750 (mm(2)) of superior [0.101 (0.09)], inferior [0.105 (0.09)], superior-nasal [0.111 (0.09)] and superior-temporal [0.117 (0.09)] sectors were smaller compared with other sectors (P < 0.05). The nasal iris volume (mm(3)) was the smallest compared with other quadrants for the entire cohort [nasal 8.18 (1.2) < inferior 9.13 (1.3) < temporal 9.16 (1.2) < superior 9.33 (1.3), P < 0.001], as well as for open- and closed-angle groups. CONCLUSIONS: The irido-corneal angle was narrower in the superior, inferior, superior-nasal and superior-temporal sectors compared with other sectors. Iris volume in the nasal quadrant was the smallest compared with the other quadrants.

Development of a score and probability estimate for detecting angle closure based on anterior segment optical coherence tomography.

PURPOSE: To develop a score along with an estimated probability of disease for detecting angle closure based on anterior segment optical coherence tomography (AS OCT) imaging. DESIGN: Cross-sectional study. METHODS: A total of 2047 subjects 50 years of age and older were recruited from a community polyclinic in Singapore. All subjects underwent standardized ocular examination including gonioscopy and imaging by AS OCT (Carl Zeiss Meditec). Customized software (Zhongshan Angle Assessment Program) was used to measure AS OCT parameters. Complete data were available for 1368 subjects. Data from the right eyes were used for analysis. A stepwise logistic regression model with Akaike information criterion was used to generate a score that then was converted to an estimated probability of the presence of gonioscopic angle closure, defined as the inability to visualize the posterior trabecular meshwork for at least 180 degrees on nonindentation gonioscopy. RESULTS: Of the 1368 subjects, 295 (21.6%) had gonioscopic angle closure. The angle closure score was calculated from the shifted linear combination of the AS OCT parameters. The score can be converted to an estimated probability of having angle closure using the relationship: estimated probability = e(score)/(1 + e(score)), where e is the natural exponential. The score performed well in a second independent sample of 178 angle-closure subjects and 301 normal controls, with an area under the receiver operating characteristic curve of 0.94. CONCLUSIONS: A score derived from a single AS OCT image, coupled with an estimated probability, provides an objective platform for detection of angle closure.

Assessment of trabecular meshwork width using swept source optical coherence tomography.

PURPOSE: Measurements of the angle width by ultrasound biomicroscopy or anterior segment optical coherence tomography are usually performed 500 µm from the scleral spur, as the anterior part of trabecular meshwork (TM) is assumed to lie within this distance. The aim of this study was to measure TM width using swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan), and to investigate factors influencing this measurement. METHODS: Participants underwent gonioscopy and SS-OCT imaging in the dark. High-definition SS-OCT images were corrected for refractive distortion; and customized software (ImageJ; National Institutes of Health, Bethesda, MD, USA) was utilized to measure TM width (distance between the scleral spur and Schwalbe's line). Linear regression analysis was performed to assess the relationship between TM width with demographic and angle parameters. RESULTS: One hundred and forty eight Chinese subjects were analyzed. The majority was female (62.4 %); the mean age was 59.2 ± 8.68 years. Identification of the scleral spur and Schwalbe's line with SS-OCT was possible in 590 (99.7 %) and 585 angle quadrants (98.8 %) respectively. TM width was wider in the inferior and superior quadrants (mean 889 [SD 138] and 793 [136] µm), compared to the nasal and temporal quadrants (712 [137] and 724 [115] µm, P<0.001). There was a difference in average TM width between open (789 [100]) and closed angle eyes (753 [86]) (P=0.048). There was no significant association between TM width and angle parameters, laterality, or demographic factors. CONCLUSIONS: In SS-OCT HD images, the mean TM width varied from 710 to 890 µm in the different quadrants of the eye, and the inferior quadrant TM was the widest compared to other quadrants.

Relationship between intraocular pressure and angle configuration: an anterior segment OCT study.

PURPOSE: To assess the relationship between intraocular pressure (IOP) and anterior chamber angle (ACA) configuration as assessed by gonioscopy and anterior segment optical coherence tomography (AS-OCT). METHODS: A total of 2045 subjects aged 50 years and older, were recruited from a community clinic and underwent AS-OCT, Goldmann applanation tonometry, and gonioscopy. A quadrant was classified as closed on gonioscopy if the posterior trabecular meshwork could not be seen. A closed quadrant on AS-OCT was defined by the presence of any contact between the iris and angle wall anterior to the scleral spur. Customized software (Zhongshan Angle Assessment Program, Guangzhou, China) was used to measure AS-OCT parameters on AS-OCT scans, including anterior chamber depth, area, and volume; iris thickness (IT) and curvature; lens vault; angle opening distance; and trabecular-iris space area. IOP values were adjusted for age, sex, diabetes and hypertension status, body mass index, central corneal thickness, and presence of peripheral anterior synechiae. RESULTS: Mean age of study subjects was 63.2 ± 8.0 years, 52.6% were female, and 89.4% were Chinese. Mean IOP was 14.8 ± 2.4 mm Hg (range 826). IOP (mean ± SE) increased with number of quadrants with gonioscopic angle closure (none: 14.6 ± 0.2; one: 14.7 ± 0.3; two: 15.0 ± 0.3; three: 15.0 ± 0.3; four: 15.6 ± 0.3 mm Hg; P < 0.001), and on AS-OCT (none: 14.7 ± 0.2; one: 15.0 ± 0.2; two: 14.8 ± 0.2; three: 15.1 ± 0.3; four: 16.0 ± 0.3 mm Hg; P < 0.001). IOP also increased in association with most of the ACA quantitative parameters measured on AS-OCT images, except for IT and lens vault. CONCLUSIONS: There was an association between the extent of angle closure, as assessed on AS-OCT and gonioscopy, with increasing IOP.

Classification algorithms based on anterior segment optical coherence tomography measurements for detection of angle closure.

OBJECTIVE: A recent study found that a combination of 6 anterior segment optical coherence tomography (ASOCT) parameters (anterior chamber area, volume, and width [ACA, ACV, ACW], lens vault [LV], iris thickness at 750 µm from the scleral spur, and iris cross-sectional area) explain >80% of the variability in angle width. The aim of this study was to evaluate classification algorithms based on ASOCT measurements for the detection of gonioscopic angle closure. DESIGN: Cross-sectional study. PARTICIPANTS: We included 2047 subjects aged ≥50 years. METHODS: Participants underwent gonioscopy and ASOCT (Carl Zeiss Meditec, Dublin, CA). Customized software (Zhongshan Angle Assessment Program, Guangzhou, China) was used to measure ASOCT parameters in horizontal ASOCT scans. Six classification algorithms were considered (stepwise logistic regression with Akaike information criterion, Random Forest, multivariate adaptive regression splines, support vector machine, naïve Bayes' classification, and recursive partitioning). The ASOCT-derived parameters were incorporated to generate point and interval estimates of the area under the receiver operating characteristic (AUC) curves for these algorithms using 10-fold cross-validation as well as 50:50 training and validation. MAIN OUTCOME MEASURES: We assessed ASOCT measurements and angle closure. RESULTS: Data on 1368 subjects, including 295 (21.6%) subjects with gonioscopic angle closure were available for analysis. The mean (±standard deviation) age was 62.4±7.5 years and 54.8% were females. Angle closure subjects were older and had smaller ACW, ACA, and ACV; greater LV; and thicker irides (P<0.001 for all). For both, the 10-fold cross-validation and the 50:50 training and validation methods, stepwise logistic regression was the best algorithm for detecting eyes with gonioscopic angle closure with testing set AUC of 0.954 (95% confidence interval [CI], 0.942-0.966) and 0.962 (95% CI, 0.948-0.975) respectively, whereas recursive partitioning had relatively the poorest performance with testing set AUC 0.860 (95% CI, 0.790-0.930) and 0.905 (95% CI, 0.876-0.933), respectively. This algorithm performed similarly well (AUC, 0.957) in a second independent sample of 200 angle closure subjects and 302 normal controls. CONCLUSIONS: A classification algorithm based on stepwise logistic regression that used a combination of 6 parameters obtained from a single horizontal ASOCT scan identified subjects with gonioscopic angle closure>95% of the time. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Determinants of lens vault and association with narrow angles in patients from Singapore.

PURPOSE: To describe the distribution and determinants of lens vault and to investigate the association of lens vault with narrow angles. DESIGN: Prospective cross-sectional study. METHODS: Phakic subjects 50 years and older were evaluated at a primary healthcare clinic with gonioscopy, partial laser interferometry, and anterior segment optical coherence tomography (AS-OCT). Narrow angles were defined as posterior trabecular meshwork not visible for ≥2 quadrants on non-indentation gonioscopy. Lens vault was defined as the perpendicular distance between the anterior pole of the crystalline lens and the horizontal line joining the 2 scleral spurs on horizontal AS-OCT scans. Analysis of covariance, multivariate logistic regression, and area under the receiver operating characteristic curves (AUC) were performed. RESULTS: Of the 2047 subjects recruited, 582 were excluded because of poor image quality or inability to locate scleral spurs, leaving 1465 subjects for analysis. Eyes with narrow angles had greater lens vault compared to eyes with open angles (775.6 µm vs 386.5 µm, P < .0001). Women had significantly greater lens vault than men (497.28 µm vs 438.56 µm, P < .001), and lens vault increased significantly with age (P for trend <.001). Adjusted for age and sex, significant associations with greater lens vault were shorter axial length, shallower anterior chamber depth(ACD), higher intraocular pressure, and more hyperopic spherical equivalent (all P < .001). On multivariate analysis, subjects with lens vault >667.6 µm were more likely to have narrow angles (OR 2.201, 95% CI: 1.070-4.526) compared to those with lens vault ≤462.7 µm. The AUC for lens vault (0.816) and ACD (0.822) for detecting narrow angles were similar (P = .582). CONCLUSIONS: Lens vault was independently associated with narrow angles and may be useful in screening to detect eyes with narrow angles.

Association of narrow angles with anterior chamber area and volume measured with anterior-segment optical coherence tomography.

OBJECTIVES: To describe the measurement of anterior chamber area and anterior chamber volume by anterior-segment optical coherence tomography and to investigate the association of these parameters with the presence of narrow angles. METHODS: This was a cross-sectional study of subjects aged at least 50 years without ophthalmic symptoms recruited from a community clinic. All participants underwent standardized ocular examination and anterior-segment optical coherence tomography. Customized software was used to measure anterior chamber area (cross-sectional area bounded by the corneal endothelium, anterior surface of iris, and lens within the pupil) and anterior chamber volume (calculated by rotating the anterior chamber area 360° around a vertical axis through the midpoint of the anterior chamber area). An eye was considered to have narrow angles if the posterior pigmented trabecular meshwork was not visible for at least 180° on gonioscopy with the eye in the primary position. RESULTS: A total of 1922 subjects were included in the final analyses, 317 (16.5%) of whom had narrow angles. Mean anterior chamber area (15.6 vs 21.1 mm(2); P < .001) and anterior chamber volume (97.6 vs 142.1 mm(3); P < .001) were smaller in eyes with narrow angles compared with those in eyes without narrow angles. After adjusting for age, sex, anterior chamber depth, axial length, and pupil size, smaller anterior chamber area (odds ratio, 53.2; 95% confidence interval, 27.1-104.5) and anterior chamber volume (odds ratio, 40.2; 95% confidence interval, 21.5-75.2) were significantly associated with the presence of narrow angles. CONCLUSION: Smaller anterior chamber area and anterior chamber volume were independently associated with narrow angles in Singaporeans, even after controlling for other known ocular risk factors.

Single versus sequential testing with scanning peripheral anterior chamber depth analyser, IOLMaster and anterior segment optical coherence tomography for the detection of narrow angles.

BACKGROUND: Scanning peripheral anterior chamber depth analyser (SPAC), IOLMaster and anterior segment optical coherence tomography (AS-OCT) are devices that can screen non-invasively for narrow angles (NAs) and may reduce the need for gonioscopy, especially where the availability of ophthalmologists is limited. When used individually to detect NAs, neither SPAC, AS-OCT nor IOLMaster were able to achieve both high sensitivity and specificity when using gonioscopy as a gold standard. AIMS: To assess whether sequential testing improves discrimination of NAs over single testing. METHODS: In a prospective community-based cross-sectional study in Singapore, 2047 phakic right eyes underwent SPAC, IOLMaster and AS-OCT. NA eyes were defined as present when Shaffer scores were 0 or 1 in ≥ 2 quadrants on gonioscopy. Sensitivities and specificities of single and sequential testing were compared. RESULTS: At a fixed specificity of 95%, sensitivities in detecting NA eyes were 57.8% (95% CI 52.7% to 62.7%) for SPAC, 43.3% (95% CI 38.3% to 48.3%) for IOLMaster and 52.1% (95% CI 46.4% to 57.7%) for AS-OCT. After sequential testing using SPAC followed by AS-OCT, the sensitivity rose to 70.3% (95% CI 65.5% to 74.8%) while specificity remained at 94.3% (95% CI 93.1% to 95.4%), with sensitivity significantly higher than single testing alone (p<0.001). CONCLUSION: Sequential testing significantly improves the accuracy of detecting NAs and may be useful in screening settings.

Diagnostic performance of anterior chamber angle measurements for detecting eyes with narrow angles: an anterior segment OCT study.

OBJECTIVE: To assess the diagnostic performance of angle measurements from anterior segment optical coherence tomography (AS-OCT) images for identifying eyes with narrow angles. METHODS: We conducted a community-based cross-sectional study of individuals 50 years or older who had phakic eyes and who underwent AS-OCT imaging in the dark by a single operator and gonioscopy by an ophthalmologist masked to AS-OCT findings. An eye was considered to have narrow angles if the posterior pigmented trabecular meshwork was not visible for at least 180° on gonioscopy. Horizontal AS-OCT images were analyzed for the following measurements using customized software: angle opening distance (AOD) at 250, 500, and 750 µm from the scleral spur; trabecular-iris space area (TISA) at 500 and 750 µm; and angle recess area (ARA) at 750 µm. Areas under the receiver operating characteristic curves (AUCs) were generated for AOD, TISA, and ARA to assess the performance of these measurements in detecting eyes with narrow angles. RESULTS: Of 2047 individuals examined, 582 were excluded mostly because of poor image quality or inability to locate the scleral spur. Of the remaining 1465 participants, 315 (21.5%) had narrow angles on gonioscopy. Mean (SD) age was 62.7 (7.7) years, 54.1% were women, and 90.0% were Chinese. The AUCs were highest for AOD750 in the nasal (0.90 [95% confidence interval, 0.89-0.92]) and temporal (0.91 [0.90-0.93]) quadrants. CONCLUSIONS: The AOD750 is the most useful angle measurement for identifying individuals with gonioscopic narrow angles in gradable AS-OCT images. Poor definition of the scleral spur precludes quantitative analysis in approximately 25% of AS-OCT images.

Novel association of smaller anterior chamber width with angle closure in Singaporeans.

PURPOSE: To describe variations in anterior chamber width (ACW) and investigate its association with the presence of narrow angles. DESIGN: Cross-sectional study. PARTICIPANTS: We recruited 2047 subjects aged 50 years or more from a community polyclinic and 111 subjects with primary angle closure (PAC) or primary angle closure glaucoma (PACG) from an eye hospital in Singapore. METHODS: All participants underwent gonioscopy, anterior chamber depth (ACD) and axial length (AL) measurement (IOLMaster; Carl Zeiss, Jena, Germany), and anterior-segment optical coherence tomography (AS-OCT, Visante, Carl Zeiss Meditec, Dublin, CA). Customized software was used to measure the ACW, defined as the distance between the scleral spurs in the horizontal (nasal-temporal) axis of AS-OCT scans. An eye was deemed to have narrow angles if the posterior trabecular meshwork was not visible for at least 180 degrees on non-indentation gonioscopy with the eye in the primary position. MAIN OUTCOME MEASURES: Anterior chamber width and narrow angles. RESULTS: Data on 1465 community-based subjects were available for analysis. Anterior chamber width was significantly smaller in women compared with men (11.70 mm vs. 11.81 mm, respectively, P<0.001) and decreased significantly with age (P for trend <0.001). Significant predictors of smaller ACW were lower educational level, lower body mass index, shorter AL, shallower ACD, and Chinese race. Of the 1465 subjects, 315 (21.5%) had narrow angles on gonioscopy. Mean ACW was smaller in eyes with narrow angles compared with those without narrow angles (11.60 mm vs. 11.80 mm, P<0.001). The age- and gender-adjusted odds ratio for the highest quartile compared with the lower 3 quartiles of ACW with the presence of narrow angles was 3.4 (95% confidence interval, 2.3-5.0; P for trend <0.001). Hospital-based subjects with PAC/PACG had even smaller ACW than community subjects with narrow angles (11.33 mm vs. 11.60 mm, P<0.001). CONCLUSIONS: In this cross-sectional study, ACW was smaller in women, Chinese persons, and older persons, and was associated with narrow angles in 2 different study populations. These data suggest that a smaller ACW may represent a novel risk indicator for angle closure.

Quantitative iris parameters and association with narrow angles.

PURPOSE: To investigate the relationship between quantitative iris parameters (iris curvature [I-Curv], iris area [I-Area], and iris thickness) and the presence of narrow angles. DESIGN: Cross-sectional, community-based study. PARTICIPANTS: We recruited 2047 subjects >50 years old without ophthalmic symptoms from a community clinic in Singapore. METHODS: All subjects underwent gonioscopy and anterior segment optical coherence tomography (AS-OCT) under dark conditions. An eye was considered to have narrow angles if the posterior pigmented trabecular meshwork was not visible for >/=180 degrees on nonindentation gonioscopy with the eye in the primary position. Customized software was used on horizontal AS-OCT scans to measure I-Curv, I-Area, and iris thickness 750 mum (IT750) and 2000 mum (IT2000) from the scleral spur. The average of both temporal and nasal measured values of the right eye was used for analysis. MAIN OUTCOME MEASURES: The association between iris parameters and narrow angles on gonioscopy. RESULTS: Iris parameters from 1465 eyes (71.6%) were available for analysis. Of these, 315 subjects (21.5%) had narrow angles. The mean I-Curv (0.366 vs 0.259 mm; P<0.020), IT750 (0.476 vs 0.453 mm; P<0.001), and IT2000 (0.491 vs 0.482 mm; P = 0.010) were greater in persons with than without narrow angles. After adjusting for age, gender, anterior chamber depth, axial length, and pupil size, the greater I-Curv, I-Area, IT750, and IT2000 were significantly associated with narrow angles (odds ratio [OR] 2.5 and 95% confidence interval [CI], 1.3-5.1; OR, 2.7 and 95% CI, 1.6-4.8; OR, 2.6 and 95% CI, 1.6-4.1; OR, 2.7 and 95% CI, 1.5-4.7, comparing 4th with 1st quartile for each parameter, respectively). In stratified analysis, women and subjects aged >/=60 years had stronger associations for most iris parameters with narrow angles than men and younger subjects. CONCLUSIONS: Quantitative iris parameters (I-Curv, I-Area, and iris thickness) are independently associated with narrow angles, particularly in women and older subjects. These data provide further insights into the pathogenesis of angle closure in Singaporeans. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Evaluation of scanning protocols for imaging the anterior chamber angle with anterior segment-optical coherence tomography.

PURPOSE: To evaluate different anterior segment-optical coherence tomography (AS-OCT) scanning protocols for detecting eyes with angle closure. METHODS: This cross-sectional study enrolled 2104 subjects from a community clinic in Singapore. All participants underwent AS-OCT imaging in the dark (Visante, Carl-Zeiss, Meditec, Dublin, CA), and gonioscopy with a Goldmann 2-mirror and a Sussman lens by an experienced examiner. The anterior chamber angle in a particular quadrant was considered closed on gonioscopy if the posterior trabecular meshwork could not be seen; and on AS-OCT by the presence of contact between the iris and angle wall anterior to the scleral spur. Protocols using combinations of AS-OCT scans of different quadrants of the eye were compared. RESULTS: A total of 1853/2104 right eyes could be graded in all 4 quadrants. In all, 380 (20.5%) eyes had closed angles in at least 2 quadrants on gonioscopy. The AS-OCT scanning protocol that only imaged the inferior quadrant showed the best area under the receiving operating characteristic curve (AUC 0.76, sensitivity 84%, specificity 69%) for detecting angle closure. Although technically easier to obtain, the protocol that only included the nasal-temporal quadrants had the lowest AUC (AUC 0.67, sensitivity 47%, specificity 88%), whereas scanning the superior-inferior quadrants showed high sensitivity for detecting angle closure (92%), but low specificity (54%). CONCLUSIONS: Using the results obtained in a research setting, the diagnostic performance of AS-OCT varied according to the adopted scanning protocol. The inferior quadrant-only protocol showed the best diagnostic performance but the low specificity would limit its use for population screening.

Comparison of slitlamp optical coherence tomography and scanning peripheral anterior chamber depth analyzer to evaluate angle closure in Asian eyes.

OBJECTIVE: To evaluate the effectiveness of slitlamp optical coherence tomography (SL-OCT) and Scanning Peripheral Anterior Chamber depth analyzer (SPAC) in detecting angle closure, using gonioscopy as the reference standard. METHODS: A total of 153 subjects underwent gonioscopy, SL-OCT, and SPAC. The anterior chamber angle (ACA) was classified as closed on gonioscopy if the posterior trabecular meshwork could not be seen; with SL-OCT, closure was determined by contact between the iris and angle wall anterior to the scleral spur; and with SPAC by a numerical grade of 5 or fewer and/or a categorical grade of suspect or potential. RESULTS: A closed ACA was identified in 51 eyes with gonioscopy, 86 eyes with SL-OCT, and 61 eyes with SPAC (gonioscopy vs SL-OCT, P < .001; gonioscopy vs SPAC, P = .10; SL-OCT vs SPAC, P < .001; McNemar test). Of the 51 eyes with a closed ACA on gonioscopy, SL-OCT detected a closed ACA in 43, whereas SPAC identified 41 (P = .79). An open angle in all 4 quadrants was observed in 102 eyes with gonioscopy, but SL-OCT and SPAC identified 43 and 20 of these eyes, respectively, as having angle closure. The overall sensitivity and specificity for SL-OCT were 84% and 58% vs 80% and 80% for SPAC. CONCLUSION: Using gonioscopy as the reference, SL-OCT and SPAC showed good sensitivity for detecting eyes at risk of angle closure.