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PurposeTo evaluate the biomechanical properties of the iris by evaluating iris movement during pupil constriction and to compare such properties between healthy and primary angle-closure glaucoma (PACG) subjects.MethodsA total of 140 subjects were recruited for this study. In a dark room, the anterior segments of one eye per subject were scanned using anterior segment optical coherence tomography (AS-OCT, SS-1000 CASIA, Tomey Corporation, Nagoya, Japan) imaging during induced pupil constriction with an external white light source of 1700 lux. Using a custom segmentation code, we automatically isolated the iris segments from the AS-OCT images, which were then discretized and transformed into a three-dimensional point cloud. For each iris, a finite element (FE) mesh was constructed from the point cloud, and an inverse FE simulation was performed to match the clinically observed iris constriction in the AS-OCT images. Through this optimization process, we were able to identify the elastic modulus and permeability of each iris.ResultsFor all 140 subjects (95 healthy and 45 PACG of Indian/Chinese ethnicity, Age: 60.2±8.7 for PACG subjects and 57.7±10.1 for healthy subjects), the simulated deformation pattern of the iris during pupil constriction matched well with OCT images. We found that the iris stiffness was higher in PACG than in healthy controls (24.5±8.4 kPa vs 17.1±6.6 kPa with 40 kPa of active stress specified in the sphincter region; p < 0.001), whereas iris permeability was lower (0.41±0.2 mm2/kPa.s vs 0.55±0.2 mm2/kPa.s; p = 0.142).ConclusionThis study suggests that the biomechanical properties of the iris in PACG are different from those in healthy controls. An improved understanding of the biomechanical behavior of the iris may have implications for the understanding and management of angle-closure glaucoma.

Purpose To define the shape of the anterior surface of the peripapillary sclera (PPS) and evaluate its relationship with age and ocular determinants in a population-based Chinese cohort. Methods The optic nerve heads of 619 healthy Chinese subjects were imaged with spectral-domain optical coherence tomography. To assess the shape of the PPS/Bruch's membrane (BM), we measured the angle between a line parallel to the nasal anterior PPS/BM boundary and one parallel to the temporal side. A negative value indicated that the PPS/BM followed an inverted v-shaped configuration (peak pointing toward the vitreous), whereas a positive value indicated that it followed a v-shaped configuration (peak pointing toward the orbital tissues). A linear regression model was used to evaluate the relationship between the PPS angle and other ocular parameters. Results The mean PPS angle was 3.68° ± 6.73° and the BM angle was 9.69° ± 5.05°. The PPS angle increased on average by 0.233 deg/y. A v-shaped PPS was significantly associated with age (β = 0.087, P = 0.004), peripapillary choroidal thickness (β = −0.479, P < 0.001), lamina cribrosa depth (β = 0.307, P < 0.001), and BM angle (β = 0.487, P < 0.001) after adjusting for best corrected visual acuity, central corneal thickness, and axial length. Conclusions The anterior surface of PPS of an elderly adult population had a v-shaped configuration and was more pronounced with increasing age, thin peripapillary choroid, and a deep cup. Such a change in shape with age could have an impact on the biomechanical environment of the optic nerve head.

Purpose To compare in vivo lamina cribrosa (LC) strains (deformations) following acute IOP elevation in healthy, glaucoma, and ocular hypertensive subjects. Methods There were 20 healthy, 20 high-tension primary open-angle glaucoma (POAG), 16 primary angle-closure glaucoma (PACG), and 20 ocular hypertensive (OHT; with normal visual fields) eyes studied. For each test eye, the optic nerve head was imaged three times (at baseline IOP, following an acute elevation of IOP to approximately 35 then 45 mm Hg using an ophthalmodynamomter) using optical coherence tomography (OCT). A three-dimensional (3D) strain-mapping algorithm was applied to both sets of baseline and IOP-elevated OCT volumes to extract IOP-induced 3D strains. Octant-wise LC strains were also extracted to study the pattern of local deformation. Results The average LC strain in OHT subjects (3.96%) was significantly lower than that measured in healthy subjects (6.81%; P < 0.05). On average, POAG subjects experienced higher strain than the PACG subjects (4.05%), healthy subjects experienced higher strains than the POAG and PACG subjects, but these difference were not statistically significant. Local LC deformations showed lowest strain in the infero-temporal and temporal octant in the POAG and OHT subjects. Conclusions We demonstrate measurable LC strains in vivo in humans as a response to acute IOP elevation. In this population, our data suggest that OHT LCs experience lower IOP-induced strains than healthy LCs.

PURPOSE. Primary open-angle glaucoma (POAG) can be associated with abnormal ocular motor behavior, possibly as a compensatory strategy following visual field loss. The aim of this study was to explore the characteristics of saccadic eye movements in patients with early-stage POAG without any detectable glaucomatous visual field loss (i.e., preperimetric POAG). METHODS. Binocular eye movements were explored in 16 patients with bilateral preperimetric POAG and 16 age-matched healthy controls in a cross-sectional, observational study. Visually guided horizontal prosaccades (58, 108, 158, and 208 amplitude) and antisaccades (128 amplitude) were measured using infrared oculography. The latency, average and peak velocities, amplitude and gain of prosaccades as well as the percentage of errors in the antisaccades task were compared between groups. RESULTS. POAG patients exhibited a reduced average velocity of saccades compared to controls across all amplitudes of peripheral visual target presentation (P = 0.03). Saccades performed by POAG patients were hypometric, and with reduced amplitude (P = 0.007) and gain (P = 0.01) compared to controls. On average, POAG patients displayed more antisaccade errors (40.6%), as compared to controls (23.4%; P = 0.04). CONCLUSIONS. Here, we show that patients with POAG without detectable glaucomatous visual field loss exhibit altered saccadic eye movements. These abnormalities may indicate disordered cortical and subcortical saccadic regulation, either on the basis of subthreshold visual impairment, or as a result of wider disease-associated neurodegeneration. Additional studies, controlling for glaucoma medications, are required to delineate the neural basis of eye movement abnormalities associated with POAG.

Purpose To measure lamina cribrosa (LC) strains (deformations) following abduction and adduction in healthy subjects and to compare them with those resulting from a relatively high acute intraocular pressure (IOP) elevation. Methods A total of 16 eyes from 8 healthy subjects were included. Among the 16 eyes, 11 had peripapillary atrophy (PPA). For each subject, both optic nerve heads (ONHs) were imaged using optical coherence tomography (OCT) at baseline (twice), in different gaze positions (adduction and abduction of 20°) and following an acute IOP elevation of approximately 20 mm Hg from baseline (via ophthalmodynamometry). Strains of LC for all loading scenarios were mapped using a three-dimensional tracking algorithm. Results In all 16 eyes, LC strains induced by adduction and abduction were 5.83% ± 3.78% and 3.93% ± 2.57%, respectively, and both significantly higher than the control strains measured from the repeated baseline acquisitions (P < 0.01). Strains of LC in adduction were on average higher than those in abduction, but the difference was not statistically significant (P = 0.07). Strains of LC induced by IOP elevations (on average 21.13 ± 7.61 mm Hg) were 6.41% ± 3.21% and significantly higher than the control strains (P < 0.0005). Gaze-induced LC strains in the PPA group were on average larger than those in the non-PPA group; however, the relationship was not statistically significant. Conclusions Our results confirm that horizontal eye movements generate significant ONH strains, which is consistent with our previous estimations using finite element analysis. Further studies are needed to explore a possible link between ONH strains induced by eye movements and axonal loss in optic neuropathies.

Purpose To compare ocular biometric and anterior segment parameters between the affected and fellow eye in subjects with acute primary angle closure (APAC). Methods We evaluated 76 subjects with unilateral APAC who had undergone bilateral laser peripheral iridotomy before enrollment. Imaging was done using anterior segment optical coherence tomography and a customized software was used to measure the following: angle opening distance (AOD750); trabecular-iris space area (TISA750); iris thickness (IT750); iris curvature (ICURV); iris area (IAREA); anterior chamber depth; area and volume (ACD; ACA and ACV); anterior chamber width (ACW); anterior vault (ACD+LV); lens vault (LV); and pupil diameter (PD). We used A-scan ultrasonography to measure axial length (AL) and lens thickness (LT). Mean differences in ocular biometric and anterior segment parameters were assessed using linear mixed model adjusting for PD. Results A total of 53 subjects (36 females, 67.9%) with a mean age of 62.7 ± 8.1 years were analyzed after excluding 17 unanalyzable images in at least one eye. Affected eyes had shallower ACD, smaller ACA, ACV, anterior vault, TISA750, AOD750, and ICURV (all P < 0.05). Axial length, ACW, LV, LT, IAREA, and IT750 did not differ between the eyes. In the affected eyes, IT750 was significantly associated AOD750 (P < 0.05); whereas in the fellow eyes, IT750 and AL was predictive of AOD750 (all P < 0.05). Conclusions Eyes with previous APAC had smaller anterior segment dimensions when compared with their fellow eyes. Iris thickness was the strongest predictor of angle width in both affected and fellow eyes.

Purpose The purpose of this study was to estimate and compare changes in anterior lamina cribrosa (LC) morphology in normal, ocular hypertensive (OHT), and glaucomatous eyes following acute elevations in intraocular pressure (IOP). Methods The optic nerve heads (ONHs) of 97 subjects (17 OHT, 19 primary open-angle glaucoma [POAG], 31 primary angle-closure glaucoma [PACG], and 30 normal subjects) were imaged using optical coherence tomography (OCT). Intraocular pressure was raised twice by applying forces to the anterior sclera, using an ophthalmodynamometer. After each IOP elevation, IOP was held constant and measured; each ONH was rescanned with OCT. In each OCT volume, the anterior LC was enhanced, delineated, and its global shape index (GSI) calculated and compared across groups. Results The baseline IOP was 17.5 ± 3.5 mm Hg and was increased to 38 ± 5.9 mm Hg and then to 46.5 ± 5.9 mm Hg. At the first IOP increment, mean GSI was significantly smaller than that at baseline in normal subjects and glaucoma subjects (P < 0.05) but not in OHT subjects (P = 0.12). For the second IOP increment, the mean GSI was significantly smaller than that at baseline in normal subjects and in OHT eyes (P < 0.05). After adjusting for age, sex, and baseline IOP, the LC of POAG eyes was found to be significantly more posteriorly curved than that of normal subjects (P = 0.04). Conclusions Acute IOP elevations altered anterior LC shape in a complex nonlinear fashion. The LC of POAG eyes was more cupped following acute IOP elevations compared to that of normal subjects.

Purpose We combined finite element (FE) analysis and dynamic magnetic resonance imaging (MRI) to estimate optic nerve head (ONH) strains during horizontal eye movements, and identified factors influencing such strains. We also compared ONH strains (prelamina, lamina cribrosa, and retrolamina strains) induced by eye movements to those induced by IOP. Methods The ocular globes and orbits of a healthy subject were visualized during horizontal eye movements (up to 13°), using dynamic MRI. A baseline FE model of one eye was reconstructed in the primary gaze position, including details from the orbital and ONH tissues. Finite element-derived ONH strains induced by eye movements were compared to those resulting from an IOP of 50 mm Hg. Finally, a FE sensitivity study was performed, in which we varied the stiffness of all ONH connective tissues, to understand their influence on ONH strains. Results Our models predicted that, during horizontal eye movements, the optic nerve pulled the ONH posteriorly. Optic nerve head strains following a lateral eye movement of 13° were large and higher than those resulting from an IOP of 50 mm Hg. These results held true even with variations in connective tissue stiffness. We also found that stiff sclerae reduced lamina cribrosa and prelamina strains during eye movements, but stiff optic nerve sheaths significantly increased those strains. Conclusions Our models predicted high ONH strains during eye movements, which were aggravated with stiffer optic nerve sheaths. Further studies are needed to explore links between ONH strains induced by eye movements and axonal loss in glaucoma.

To characterize an optical coherence tomography (OCT)-derived parameter, Bruch's membrane opening-minimum rim width (BMO-MRW), and its association with demographic and clinical parameters in normal Chinese subjects.Right eyes of 466 consecutive healthy subjects from a population-based study of Singaporean Chinese underwent Cirrus OCT imaging. The retinal internal limiting membrane (ILM) and BMO were automatically delineated using the built-in Cirrus algorithm. The standard 36 interpolated radial B-scans (72 BMO points, 5° increments) of each optic nerve head were manually extracted from the central circle (3.46-mm diameter). We used Matlab to measure the shortest distance from the BMO points to the ILM. Associations of BMO-MRW with demographic and clinical parameters were evaluated using marginal general estimating equations analysis.There was a slight preponderance of male subjects (50.9%), with a mean age of 54.8 ± 7.63 years. Mean BMO-MRW was 304.67 ± 58.96 μm (range, 173.32-529.23 μm), which was highly associated with OCT-derived disc area (DA) (β = -91.78, P0.001) and rim area (RA) (β = 194.31, P0.001), followed by spherical refractive error (SRE) (β = -2.23, P = 0.02) and retinal nerve fiber layer (RNFL) thickness (β = 0.5, P = 0.04), after adjusting for the associated factors such as age, sex, intraocular pressure (IOP), and vertical cup-disc ratio (VCDR).Disc area and RA had the strongest association with BMO-MRW, followed by SRE and RNFL thickness. The availability of this normative database will facilitate optic nerve head assessment using the BMO-MRW parameter in Chinese subjects.

PURPOSE We evaluated changes in choroidal thickness (ChT), IOP, ocular biometry, and serum osmolality after the water drinking test (WDT) in subjects with previous acute primary angle closure (APAC) and primary angle closure glaucoma (PACG). METHODS We evaluated 38 subjects, including 21 with APAC and 17 with PACG. Each subject underwent IOP measurement, A-scan biometry, spectral domain-optical coherence tomography (SDOCT), anterior segment-optical coherence tomography (ASOCT), and osmolality measurements at baseline, 30, and 60 minutes after consuming at least 10 mL/kg of water. The ChT at the macula was measured from SDOCT images using the 7-line scan protocol. The fellow-eyes of APAC (FE-APAC) were compared to eyes with PACG. RESULTS The mean age ± SD of the study subjects was 62.8 ± 8.6 years and 21 (55.3%) were females. At baseline, serum osmolality was significantly lower (P < 0.001) in the FE-APAC group, whereas ChT was similar in both groups (P = 0.56). At 30 minutes after WDT, both groups demonstrated a significant increase in IOP (FE-APAC, 3.0 [95% confidence interval {CI}, 1.52, 4.48] mm Hg; PACG, 5.06 [95% CI, 3.68, 6.26] mm Hg; P < 0.001 for both) and decrease in serum osmolality (P < 0.001 for both), but no significant change in ChT. The magnitude of change in IOP was significantly greater in PACG eyes (P = 0.04). After multivariate analysis, a lower mean baseline serum osmolality (β = -0.44, P = 0.003) was associated with a greater change in ChT at 30 minutes after WDT. CONCLUSIONS The increase in IOP after WDT was higher in PACG eyes compared to FE-APAC; however, the latter had lower serum osmolality at baseline. Change in mean ChT following WDT was associated with a lower baseline serum osmolality.

PURPOSE To evaluate a novel software capable of automatically grading angle closure on EyeCam angle images in comparison with manual grading of images, with gonioscopy as the reference standard. METHODS In this hospital-based, prospective study, subjects underwent gonioscopy by a single observer, and EyeCam imaging by a different operator. The anterior chamber angle in a quadrant was classified as closed if the posterior trabecular meshwork could not be seen. An eye was classified as having angle closure if there were two or more quadrants of closure. Automated grading of the angle images was performed using customized software. Agreement between the methods was ascertained by κ statistic and comparison of area under receiver operating characteristic curves (AUC). RESULTS One hundred forty subjects (140 eyes) were included, most of whom were Chinese (102/140, 72.9%) and women (72/140, 51.5%). Angle closure was detected in 61 eyes (43.6%) with gonioscopy in comparison with 59 eyes (42.1%, P = 0.73) using manual grading, and 67 eyes (47.9%, P = 0.24) with automated grading of EyeCam images. The agreement for angle closure diagnosis between gonioscopy and both manual (κ = 0.88; 95% confidence interval [CI), 0.81-0.96) and automated grading of EyeCam images was good (κ = 0.74; 95% CI, 0.63-0.85). The AUC for detecting eyes with gonioscopic angle closure was comparable for manual and automated grading (AUC 0.974 vs. 0.954, P = 0.31) of EyeCam images. CONCLUSIONS Customized software for automated grading of EyeCam angle images was found to have good agreement with gonioscopy. Human observation of the EyeCam images may still be needed to avoid gross misclassification, especially in eyes with extensive angle closure.

PURPOSE Recently, three genetic susceptibility loci for primary angle closure glaucoma (PACG) were identified: COL11A1 rs3753841, PCMTD1-ST18 rs1015213, and PLEKHA7 rs11024102. The purpose of this study was to investigate whether these single nucleotide polymorphisms (SNPs) affect the phenotype of PACG patients. METHODS A retrospective analysis was performed for 700 Singaporean Chinese PACG patients who had been genotyped. The associations between the three SNPs and clinical features related to severity of glaucoma were studied. For a subgroup of patients who had ≥ 5 years of follow-up and ≥ 5 reliable visual field (VF) tests, differences in glaucoma progression, as measured by the proportion of VF progression and blindness, were compared among groups with different genotypes. RESULTS The minor allele frequencies at COL11A1 rs3753841, PCMTD1-ST18 rs1015213, and PLEKHA7 rs11024102 were 36%, 2.1%, and 41.5%, respectively. There were no significant differences in sex, diagnosis (acute primary angle closure [APAC] versus non-APAC), age at diagnosis, laterality of glaucoma, or need for filtration surgery among patients with different genotypes (all P > 0.05). We also found no significant difference between genotypes and the IOP at presentation, and other clinical characteristics at DNA collection (vertical cup-to-disc ratio, best corrected visual acuity, baseline VF mean deviation, or pattern standard deviation). For the subgroup analysis, we did not observe significant associations between VF progression and the proportion of blindness with any of the PACG susceptibility loci. CONCLUSIONS The three genetic susceptibility loci for PACG did not underlie any major phenotypic diversity in terms of disease severity or progression.

Purpose To determine the prevalence and types of glaucoma in an urban Singaporean Indian population. Methods The Singapore Indian Eye Study (SINDI) was a population-based, cross-sectional survey that examined 3400 (75.6% response) persons aged 40 to 80 years. Participants underwent a standardized examination including slit-lamp biomicroscopy, Goldmann applanation tonometry, and dilated optic disc assessment. Participants suspected to have glaucoma also underwent visual field examination (24-2 SITA standard, Humphrey Visual Field Analyzer II), gonioscopy, and repeat applanation tonometry. Glaucoma was defined according to International Society for Geographical and Epidemiologic Ophthalmology criteria. Results Of the 3400 participants, 78 (2.29%) had diagnosed glaucoma, giving an age-standardized prevalence of 1.95% (95% confidence interval [CI], 1.5%-2.5%). The age-standardized prevalence of primary open-angle glaucoma (POAG) was 1.25% (95% CI, 0.89%-1.73%), primary angle-closure glaucoma (PACG) 0.12% (95% CI, 0.04%-0.33%), and secondary glaucoma 0.55% (95% CI, 0.35%-0.86%). The mean IOP among the participants in the normal group in the study population was 15.6 ± 2.6 mm Hg and 17.7 ± 6.1 mm Hg in subjects with glaucoma (P = 0.003). The mean central corneal thickness (CCT) in the normal study population was 540.31 ± 33.79; the mean CCT in subjects with POAG (529.8 ± 30.8 μm) was statistically different from the normal study group (P = 0.003). Conclusions The prevalence of glaucoma among Singaporean Indians 40 years of age and older in Singapore was 1.95%, approximately half that of the Chinese and the Malay persons in Singapore. As in other Asian studies, POAG was the main form of glaucoma accounting for nearly 60% of cases.

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.

PURPOSE. To evaluate the acceleration of pupil constriction (APC) in response to illumination using video anterior segment optical coherence tomography (AS-OCT) in angle closure and normal eyes. METHODS. This was an observational study of 342 Chinese subjects. Iris and angle changes in response to illumination were captured with real-time video recordings of AS-OCT and analyzed frame by frame. APC was calculated using a quadratic function, fitting pupil diameter to a time series. APC was divided into two vector components: acceleration of pupil block (APB) acting perpendicular to the lens surface and acceleration of iris stretch (AIS) acting toward the iris root. RESULTS. Of 342 eligible patients, 306 (89.5%) were available for analysis; of whom 136 (41.7%) had angle closure. After adjusting for age, sex, baseline pupil diameter, and iris thickness, APC was significantly lower in angle closure eyes (0.61 mm/s 2 ) than in open-angle eyes (0.90 mm/s 2 )( P < 0.0001) as was AIS (0.58 mm/ s 2 vs. 0.89 mm/s 2 )( P < 0.001). APB was significantly higher in angle closure eyes compared to open-angle eyes (0.14 mm/s 2 vs. 0.09 mm/s 2 )( P < 0.001). After adjusting for age and sex in logistic regression, the magnitude and direction of all vector parameters were significantly associated with presence of angle closure. CONCLUSIONS. Angle closure eyes have smaller AIS and larger APB in response to illumination as measured using AS-OCT videography. This shows that, comparatively, the iris of angle closure eyes stretches less and develops a more convex configuration in response to illumination. (Invest Ophthalmol Vis Sci. 2012;53:6756‐6762) DOI:10.1167/iovs.12-10415

PURPOSE: To compare two spectral domain optical coherence tomography (SD-OCT) devices for the identification of angle structures and the presence of angle closure. METHODS: This was a prospective comparative study. Consecutive patients underwent gonioscopy and anterior segment imaging using two SD-OCT devices (iVue and Cirrus). Images were evaluated for the ability to detect angle structures such as Schwalbe's line (SL), trabecular meshwork (TM), Schlemm's canal (SC), and scleral spur (SS), and the presence of angle closure. Angle closure was defined as iris contact with the angle wall anterior to the SS on SD-OCT, and nonvisibility of the posterior TM on gonioscopy. Angle closure in an eye was defined as ≥two quadrants of closed angles. AC1 statistic was used to assess the agreement between devices. RESULTS: Of the 69 subjects studied (46.4% male, 84.1% Chinese, mean age 64.0 ± 10.5 years), 40 subjects (40 eyes, 58.0%) had angle closure on gonioscopy. The most identifiable structure on Cirrus SD-OCT was the SS (82.2%) and SL on iVue SD-OCT (74.5%). Angle closure was indeterminable in 14.5% and 50.7% of Cirrus and iVue scans (P < 0.001), respectively. Interdevice agreement for angle closure was moderately strong (AC1 = 0.67), but agreement with gonioscopy was only fair (AC1 = 0.35 and 0.50 for Cirrus and iVue, respectively). CONCLUSIONS: It was more difficult to determine angle closure status with iVue compared with Cirrus SD-OCT. There was fair agreement between both devices with gonioscopy for identifying angle closure.

PURPOSE To determine the ability of the RTVue spectral domain optical coherence tomography (SDOCT) to image the anterior chamber angle (ACA). METHODS Consecutive subjects, recruited from glaucoma clinics, prospectively underwent ophthalmic evaluation including gonioscopy by an ophthalmologist and anterior chamber imaging with SDOCT, adapted with a corneal lens adapter (cornea anterior module-low magnification [CAM-L]) and anterior segment OCT (ASOCT), both performed by a technician. Two different ophthalmologists, masked to gonioscopy findings, assessed visualization of the scleral spur (SS), Schwalbe's line (SL), and trabecular meshwork (TM) by the two modalities. The ability to detect a closed angle was compared with gonioscopy. RESULTS The average age (SD) of the 81 subjects enrolled was 64.1 (11.4) years; the majority were Chinese (91.4%) and female (61.7%). SDOCT images revealed the SS in 26.9% (56/324) of quadrants and the SL in 44.1% (143/324) of quadrants; in ASOCT images, the SS could be visualized in 69.1% (224/324) of quadrants (P < 0.0001), but the SL was undetectable. The TM was detected equally well (17.3%, P < 0.92) using either device. The angle status was gradable in only 41.7% images with SDOCT, compared with 71.3% of ASOCT images (P < 0.0001). ACA was classified as closed in 19.3% of quadrants (26/135) with SDOCT images and in 44.2% (102/231) with ASOCT images compared with 37.7% (122/324) on gonioscopy. When analyzing the horizontal quadrants only, both modalities agreed well with gonioscopy, 0.75 and 0.74, respectively (AC1 statistics). CONCLUSIONS The RTVue SDOCT allowed visualization of SL, TM, and SS. However, these landmarks were not detected in a large percentage of images.

PURPOSE To evaluate the ocular and systemic factors influencing measurements of optic nerve head (ONH) parameters and retinal nerve fiber layer (RNFL) thickness with spectral-domain optical coherence tomography (SD-OCT) in healthy Chinese adults. METHODS Adults ranging in age from 40 to 80 years were consecutively recruited from the population-based Singapore Chinese Eye Study. A SD-OCT instrument was used to measure ONH and RNFL parameters. A total of 542 eyes from 542 non-glaucomatous Chinese subjects were analyzed. Univariable and multiple linear regression analyses were performed to examine the effects of a range of ocular (e.g., intraocular pressure [IOP], axial length [AL], disc area) and systemic (e.g., blood pressure, serum glucose) factors on ONH and RNFL parameters. RESULTS In multiple regression analyses, neuroretinal rim area was independently associated with age (β = -0.006, P < 0.001), disc area (β = 0.183, P < 0.001), IOP (β = -0.009, P = 0.008), AL (β = -0.023, P = 0.004), and lens nuclear color (β = 0.042, P = 0.001). Vertical cup-to-disc ratio was independently correlated with age (β = 0.003, P < 0.001), disc area (β = 0.207, P < 0.001), IOP (β = 0.004, P = 0.014), AL (β = 0.010, P = 0.008), and lens nuclear color (β = -0.017, P = 0.006). Average RNFL thickness was independently related to age (β = -0.204, P = 0.001), disc area (β = 4.218, P < 0.001), signal strength (β = 1.348, P < 0.001), and AL (β = -1.332, P < 0.001). Disc area had the strongest effect on measurements of ONH parameters and RNFL thickness. CONCLUSIONS In a non-glaucomatous population, optic nerve measurements with SD-OCT vary with disc area, age, IOP, AL, lens nuclear color, and signal strength, but systemic parameters have little influence. This information may be useful for interpretation of SD-OCT measurements.

To determine the prevalence of primary open-angle glaucoma (POAG) and the associated risk factors in a rural population in southern India.Subjects aged 40 years or more (n = 3934) underwent a complete ophthalmic examination. Glaucoma was diagnosed according to the International Society of Geographical and Epidemiologic Ophthalmology classification.Complete data were available for 3924 subjects (response rate, 81.75%). In eyes with normal suprathreshold visual fields, the mean intraocular pressure was 14.29 +/- 3.32 mm Hg (97.5th and 99.5th percentiles, 21 and 25 mm Hg, respectively). The mean vertical cup-to-disc ratio was 0.39 +/- 0.17 (97.5th and 99.5th percentiles, 0.7 and 0.8, respectively). Sixty-four subjects had definite POAG (1.62%, 9.5% CI 1.42-1.82); 30 were men and 34 were women. Subjects with POAG (59.85 +/- 10.43 years) were older (P0.001) than the study population (53.78 +/- 10.71 years). In only one (1.5%) person was POAG diagnosed before the study. Two (3.12%) subjects were blind due to POAG; 21 (32.81%) subjects had a presenting IOP21 mm Hg, and 43 (67.19%) had an IOP21 mm Hg. The mean central corneal thickness in subjects with POAG (502.82 +/- 35.29 microm) was not different from that of the normal study population (505.93 +/- 31.11 microm). No association was found with diabetes mellitus, systemic hypertension, gender, and myopia. Increasing IOP (per mm Hg) was associated with the disease (OR 1.12; 95% CI, 1.08-1.16). The odds for POAG increased with advancing age after adjustment for gender.The prevalence of POAG in this population was 1.62%. The prevalence increased with age, and 98.5% were not aware of the disease.