Anterior Chamber Area Research Articles

Changes in Japanese eyes after laser peripheral iridotomy: an anterior segment optical coherence tomography study.

The aim was to investigate the changes in anterior segment parameters, as assessed by anterior segment optical coherence tomography in Japanese subjects after laser peripheral iridotomy (LPI). This was a prospective observational study. The participants include 72 subjects with angle closure including primary angle closure suspect (PACS), primary angle closure (PAC), and primary angle closure glaucoma (PACG). Anterior segment optical coherence tomography parameters was measured by customized software. Complete data of 51 subjects were available for final analysis. These were the following parameters: angle opening distance, trabecular-iris space area, anterior chamber depth, width, area and volume (iris thickness, curvature, and area, and lens vault (LV). A total of 25 PACS, 17 PAC and 9 PACG were included. Mean age was 74.7 ± 6.7 years, and majority were women (80.4%). Following LPI, there was a significant increase in mean gonioscopic angle width (1.16 vs. 1.93, P < 0.001) and a corresponding increase in angle opening distance, trabecular-iris space area, and angle recess area (all P < 0.001). The anterior chamber area (P < 0.001), anterior chamber volume (P < 0.001) and anterior chamber depth (P = 0.003) increased significantly; and iris curvature (P < 0.001) was significantly reduced. There were no significant changes in anterior chamber width, LV, iris thickness and area. Age-adjusted and gender-adjusted analysis for predictors of percentage change in angle opening distance 750 showed significant association with greater baseline LV (β = 0.32, P = 0.03). No significant differences were noted in the mean percentage change in parameters between the PACS and PAC-PACG. An increase in anterior chamber dimensions, angle widening and iris flattening; with a constant LV, iris thickness and iris area after LPI was demonstrated in Japanese eyes with angle closure.

Preoperative Biometric Parameters Predict the Vault after ICL Implantation: A Retrospective Clinical Study

Purpose: To investigate the correlation between the preoperative biometric parameters of the anterior segment and the vault after implantable Collamer lens (ICL) implantation via this retrospective study. Design: Retrospective clinical study. Methods: A total of 78 eyes from 41 patients who underwent ICL implantation surgery were included in this study. Preoperative biometric parameters, including white-to-white (WTW) diameter, central corneal thickness, keratometer, pupil diameter, anterior chamber depth, sulcus-to-sulcus diameter, anterior chamber area (ACA) and central curvature radius of the anterior surface of the lens (Lenscur), were measured. Lenscur and ACA were measured with Rhinoceros 5.0 software on the image scanned with ultrasound biomicroscopy (UBM). The vault was assessed by UBM 3 months after surgery. Multiple stepwise regression analysis was employed to identify the variables that were correlated with the vault. Results: The results showed that the vault was correlated with 3 variables: ACA (22.4 ± 4.25 mm²), WTW (11.36 ± 0.29 mm) and Lenscur (9.15 ± 1.21 mm). The regressive equation was: vault (mm) = 1.785 + 0.017 × ACA + 0.051 × Lenscur - 0.203 × WTW. Conclusions: Biometric parameters of the anterior segment (ACA, WTW and Lenscur) can predict the vault after ICL implantation using a new regression equation.

Association of Ocular Conditions With Narrow Angles in Different Ethnicities

To quantify the predictive strength of anterior chamber area (ACA), anterior chamber volume (ACV), anterior chamber width (ACW), lens vault (LV), iris thickness (IT), and iris area (IArea) for 2 angle width parameters, trabecular-iris space area (TISA750) and angle opening distance (AOD750) at 750μm from the scleral spur, in different ethnicities. Prospective, cross-sectional study. Anterior segment optical coherence tomography images for 166 white, 90 African, 75 Hispanic, and 132 Chinese subjects were analyzed. First, ACA, ACV, ACW, LV, IT, and IArea were compared among ethnic groups. Second, associations of TISA750 and AOD750 with ACA, ACV, ACW, LV, IT, and IArea were investigated within each ethnic group using multivariable linear regression models, standardized regression coefficients (β), and coefficients of determination (R(2)). Significant ethnic differences were observed in ACA, ACV, ACW, LV, IT, and IArea (all P < .05). ACA, ACV, and LV were significant predictors of TISA750 and AOD750 in all ethnic groups (all P < .001). ACW and IT were significant predictors of AOD750 in white and African subjects (all P < .05). ACW and IT were significant predictors of TISA750 in white subjects (all P < .05). IArea was a significant predictor of AOD750 in Chinese (P < .05). ACA, ACV, and LV had the highest predictive strength for both TISA750 and AOD750 in all ethnic groups based on β and R(2). Despite ethnic differences in ACA, ACV, ACW, LV, IT, and IArea, the same 3 anterior segment parameters (ACA, ACV, and LV) were the strongest predictors of angle width (TISA750 and AOD750) in all 4 ethnic groups.

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

AimTo evaluate quantitative changes in anterior segment optical coherence tomography (AS-OCT) parameters at 4 years in subjects with open angles on gonioscopy at baseline.Methods339 gonioscopically open-angle subjects aged >50 years...

Angle closure glaucoma in Asians: comparison of biometric and anterior segment parameters between Japanese and Chinese subjects

AbstractPurpose To compare anterior segment parameters in Chinese and Japanese subjects using anterior segment optical coherence tomography (ASOCT) and to determine if the associations between these parameters and angle closure vary between the two ethnic groups.Methods We conducted a case‐control study among 117 Japanese and 102 Chinese patients with primary angle closure (PAC) or primary angle closure glaucoma (PACG); and 117 Japanese and 176 Chinese controls. All participants underwent A‐scan biometry and ASOCT imaging (Visante, Carl Zeiss Meditec, Dublin, Ca). ASOCT‐derived biometric parameters were compared between groups. Multivariate analysis was performed to determine predictors of angle opening distance at 750µm from the scleral spur (AOD750).Results Japanese were older (p&lt;0.001) and consisted of more females (p&lt;0.001). Age and gender adjusted analysis of covariance showed that Japanese eyes with angle closure had a significantly shallower anterior chamber depth (p=0.015), shorter axial length (p&lt;0.001), greater lens thickness (p&lt;0.001), lens vault (LV) (p=0.001) and iris curvature (I‐Curv) (p&lt;0.001), and a smaller anterior chamber area (p=0.044) and volume (p=0.028); but no significant difference was noted for anterior chamber width (ACW). In Japanese, the predictors of AOD750 were LV (p=0.004), ACW (p=0.049) and ICurv (p=0.017); in Chinese, only the LV (p&lt;0.001) was a determinant factor.Conclusion Japanese eyes with angle closure were smaller, with thicker lenses. LV is an important factor for angle closure in both races. These results suggest differing mechanisms of angle closure pathogenesis between the two ethnic groups.

Pretreatment Anterior Segment Imaging During Acute Primary Angle Closure: Insights into Angle Closure Mechanisms in the Acute Phase

To describe anterior segment optical coherence tomography (ASOCT) parameters during acute primary angle closure (APAC) before therapeutic interventions and comparative analyses of biometric parameters of APAC eyes with fellow eyes. Prospective, comparative case series. Thirty-one consecutive patients with APAC. All patients underwent ASOCT imaging of both eyes during the attack, before therapeutic interventions were administered. Custom software was used to measure anterior chamber depth (ACD), anterior chamber area (ACA), anterior chamber volume (ACV), iris curvature (I-Curv), iris area (I-Area), lens vault (LV), and angle opening distance (AOD750), trabecular iris space area (TISA750), and iris thickness (IT750) at 750 μm from the scleral spur. Multivariate logistic regression modeling using forward selection was used to determine the most important biometric variables associated with APAC compared with the fellow eye during the attack. Anterior segment biometric parameters associated with APAC. The mean age of the patients was 60.9±7.5 years, and 11 patients (35.5%) were male. The mean intraocular pressure was 3.8±9.2 mmHg in the APAC eye and 4.2±4.3 mmHg in the fellow eye before treatment (P <0.001). After adjustment for pupil diameter, APAC eyes had smaller ACD, ACA, ACV, I-Curv (all P <0.001), AOD750 (P= 0.037), TISA750 (P= 0.043), I-Area (P= 0.027), and IT750 (P= 0.002) and larger LV (P= 0.041) than fellow eyes. An optimal model consisting of 3 variables (pupil diameter, ACD, and I-Curv) explained 36.7% of the variance in APAC occurrence, with ACD accounting for 18.1% and I-Curv accounting for 14.1% of this variance. Shallower ACD and smaller I-Curv were the 2 main anterior segment biometric parameters associated with APAC during the attack. These findings present new insights into the anterior segment biometric parameters of APAC and fellow eyes before therapeutic interventions. Anatomic changes in the anterior segment explained only about one third of the variance in APAC occurrence, and the role of nonanatomic factors require further investigation.

Comparison of anterior segment morphology following prophylactic laser peripheral iridotomy in Caucasian and Chinese eyes

To compare anterior segment biometric parameters between Caucasians and Chinese before and after laser peripheral iridotomy. Prospective clinical cohort study. Caucasian and Chinese primary angle-closure suspects. Anterior segment optical coherence tomography images captured before and after laser peripheral iridotomy were analysed to measure anterior segment biometric parameters. Paired Student's t-tests were used for within-ethnic group comparisons. Univariate and linear mixed-effect regression models were used for between-ethnic group comparisons. Angle opening distance, angle recess area, iris thickness, iris curvature, anterior chamber area, anterior chamber volume and anterior chamber width. Caucasians had significantly greater preoperative angle recess area, anterior chamber width, and iris curvature and lower preoperative iris thickness compared to Chinese (P < 0.05). Significant postoperative increases in angle opening distance, angle recess area, anterior chamber area, anterior chamber volume, and anterior chamber width along with significant postoperative decrease in iris curvature were observed within both ethnic groups (P < 0.05). However, the amount of laser peripheral iridotomy-induced changes in angle opening distance, angle recess area, anterior chamber area, anterior chamber volume, anterior chamber width, and iris curvature did not differ between the two ethnic groups (P < 0.05). Both Caucasian and Chinese demonstrated opening of anterior chamber angle width, expansion of anterior chamber dimensions, and flattening of iris convexity after laser peripheral iridotomy. Although certain aspects of anterior segment anatomy differed between Caucasians and Chinese preoperatively, they did not translate into significant ethnic differences in the amount of laser peripheral iridotomy-induced changes in the anterior segment biometric parameters.

Anterior Segment Optical Coherence Tomography Parameters in Subtypes of Primary Angle Closure

To compare anterior segment parameters, assessed by anterior segment optical coherence tomography (ASOCT), in subjects categorized as primary angle closure suspect (PACS), primary angle closure (PAC), primary angle closure glaucoma (PACG), and previous acute PAC (APAC); and to identify factors associated with APAC. This was a prospective ASOCT study of 425 subjects with angle closure (176 PACS, 66 PAC, 125 PACG, and 58 APAC). Customized software was used to measure ASOCT parameters, including angle opening distance (AOD750), trabecular-iris space area (TISA750), anterior chamber depth, width, area and volume (ACD, ACW, ACA, ACV), iris thickness (IT750), iris area (IAREA), and lens vault (LV). Mean differences in anterior segment parameters were evaluated by analysis of covariance (ANCOVA) adjusted for age, sex, and pupil diameter (PD). Comparison among the different subgroups showed that ACD, ACA, and ACV were smallest, and IT750 thickest in the APAC group compared with the other subgroups (P < 0.001). LV was greatest in the APAC group (1218 ± 34 μm) followed by PAC (860 ± 31 μm), PACG (845 ± 23 μm), and PACS (804 ± 19 μm), respectively (P = <0.001). While the APAC group had the narrowest angles, the PACS group had the widest (P < 0.001 for both AOD750 and TISA750). Logistic regression showed that greater LV (P = <0.001), narrower TISA750 (P = <0.001), and thicker IT750 (P = 0.007) were the major determinants of APAC. Eyes with APAC had the narrowest angles, smallest anterior segment dimensions, thickest iris, and largest LV compared with PACS, PAC, and PACG. LV, TISA750, and IT750 were the major determinants of APAC.

Microincision cataract surgery: 1.8 mm incisional surgery

Microincision cataract surgery (MICS) is an approach to cataract surgery through incision less than 1.8 mm with the purpose of reducing surgical invasiveness, improving at the same time surgical outcomes. The main confirmed advantages of MICS are the control and avoidance of surgically induced corneal astigmatism and the decrease of postoperative corneal aberrations. MICS has been demonstrated to be minimally traumatic surgery, providing better postoperative outcomes than standard small incision phacoemulsification. High degree of surgical innovation, use of advanced phacoemulsification surgical platforms with pressurized fluidic control and new surgical instrumentation, allow doing very sophisticated cataract surgery. MICS favors the use of fluidics, reducing the use of phacoemulsification power. Bimanuality provides opportunity to do manipulation in anterior chamber area easily and much more comfortably than with standard coaxial technique. Today, surgery is performed through 1 mm incision. The use of the modern MICS intraocular lens (IOL) requires incisions of 1.8 mm. The increased availability of MICS IOLs allows to select the best IOL as per the demand of the patient. Long-term stability of the MICS outcomes and wide range of surgical capacity makes MICS the most modern and adequate approach to minimally invasive cataract surgery.

Longitudinal Changes in Anterior Segment Parameters After Laser Peripheral Iridotomy Assessed by Anterior Segment Optical Coherence Tomography

To quantify long-term changes in anterior segment (AS) parameters after laser peripheral iridotomy (LPI) using AS optical coherence tomography (OCT) in primary angle-closure suspect (PACS). Thirty-two PACS subjects were imaged at pre-LPI and 2 weeks and 18 months post-LPI using AS OCT. Anterior chamber depth (ACD), iris curvature (IC), iris thickness at 750 and 1500 μm from the scleral spur (IT750, 1500), lens vault (LV), anterior chamber area (AA), and iris area (IA) were estimated by ImageJ software (version 1.46). Anterior chamber angle (ACA) parameters (angle opening distance [AOD750], angle recess area [ARA750], and trabecular iris space area [TISA750]) were provided by the manufacturer. Parameters were compared before and after LPI. Uni- and multivariate regression analysis was performed to evaluate factors associated with ACA narrowing. Mean AA (14.63 vs. 15.87 mm(2)) and three ACA parameters (AOD750 [0.17 vs. 0.28 mm], TISA750 [0.07 vs. 0.11 mm(2)], and ARA750 [0.08 vs. 0.13 mm(2)]) increased at 2 weeks post-LPI (all P < 0.001). The IT750, 1500 and IC also showed change at 2 weeks post-LPI. Eighteen months post-LPI, IC (0.34 vs. 0.16 mm, P < 0.001) and LV (0.88 vs. 1.01 mm, P = 0.001) were significantly different, while three ACA parameters were not different from their pre-LPI status. At post-LPI 18 months, LV was significantly associated with ACA narrowing (P = 0.026). The ACA tended to be narrowed at 18 months post-LPI despite resolution of pupillary block, which may be due to LV increment. Our results warrant continuous follow-up of narrow-angle patients after LPI.

Ocular Biometric Parameters Associated With Intraocular Pressure Reduction After Cataract Surgery in Normal Eyes

To evaluate the ocular biometric parameters associated with intraocular pressure (IOP) reduction after phacoemulsification. Prospective, observational case series. The study included 999 patients who had undergone uncomplicated phacoemulsification. IOP and ocular biometric parameters were checked preoperatively and 3months postoperatively using anterior segment optical coherence tomography, optical biometry, and ultrasonic biomicroscopy. The relationship between IOP change and the parameters, including preoperative IOP, anterior chamber depth, axial length, angle opening distance at 500μm, anterior chamber area, corneal thickness, lens thickness, and iris thickness at 750μm, was evaluated. The mean patient age was 67.1 ± 4.3 years. The average change in IOP was-1.6mm Hg (-11.8%). In univariate analysis, axial length, corneal thickness, and iris thickness were not significantly associated with IOP reduction. However, preoperative IOP, anterior chamber depth, angle opening distance, anterior chamber area, and lens thickness were significantly associated with IOP change (P < .05). Furthermore, changes in anterior chamber depth (standardized coefficient beta [B]=-0.082), angle opening distance (B=-0.095), and anterior chamber area (B=-0.380) were more strongly correlated with IOP change than were preoperative factors (B=-0.078, B=-0.071, and B=-0.067, respectively). In multivariate analysis, preoperative IOP, lens thickness, angle opening distance change, and anterior chamber area change were significantly associated with IOP change (P < .005). In addition to preoperative IOP and lens thickness, parameters such as changes in anterior chamber area and angle opening distance were significantly associated positively with reduced IOP after phacoemulsification.

Relationship between Intraocular Pressure and Angle Configuration: An Anterior Segment OCT Study

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). 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. 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. There was an association between the extent of angle closure, as assessed on AS-OCT and gonioscopy, with increasing IOP.

A Hierarchical Cluster Analysis of Primary Angle Closure Classification Using Anterior Segment Optical Coherence Tomography Parameters

To investigate the possibility of classifying angle closure eyes in terms of features provided by anterior segment optical coherence tomography (AS OCT). Angle closure (primary angle closure [PAC] or PAC glaucoma [PACG]) eyes diagnosed by gonioscopy were imaged using AS OCT under the same lighting conditions. Anterior chamber depth (ACD), anterior chamber width (ACW), iris cross-sectional area (IA), iris thickness at 750 μm from the scleral spur (IT750), iris curvature (IC), lens vault (LV), and anterior chamber area (ACA) were determined using Image J software (ver. 1.44). A hierarchical cluster analysis using Ward's method was performed using AS parameters obtained by AS OCT and axial length (AXL). A hierarchical cluster analysis was performed on 166 angle closure eyes and produced two clusters. The first cluster (84 eyes) was characterized by higher ACD (2.24 mm), higher ACA (12.5 mm(2)), higher IT750 (0.44 mm), higher ACW (11.2 mm), lower LV (0.85 mm), and higher AXL (23.5 mm) compared with the second cluster (82 eyes, 1.82 mm, 9.5 mm(2), 0.38 mm, 10.8 mm, 1.1 mm, and 22.8 mm, respectively). The second cluster had essentially higher LV and lower ACA than the first cluster. Most parameters were significantly different between two clusters except IC (P = 0.76). Our hierarchical cluster analysis indicated two clusters with quite different features existed in our total angle closure population. Our results suggest the possibility of subclassifying angle closure eyes according to AS OCT parameters.

Analysis of Anterior Segment Dynamics Using Anterior Segment Optical Coherence Tomography Before and After Laser Peripheral Iridotomy

To evaluate changes in the speed of pupil constriction and in anterior segment parameters after laser peripheral iridotomy (LPI) in patients with angle closure using anterior segment optical coherence tomography. In this prospective observational study, videos of pupil and anterior segment changes in response to illumination were captured with real-time video recording using anterior segment optical coherence tomography and were analyzed frame by frame before and after LPI. Customized software was used to measure the speed of pupil constriction and changes in anterior chamber depth and anterior chamber area, as well as iris thickness at 750 μm from the scleral spur, at the sphincter muscle region (0.75 mm from the pupillary margin), and at the mid-iris location (half the distance between the scleral spur and the pupillary margin). Pupil diameter, angle opening distance, and trabecular-iris space area at 500 μm from the scleral spur were determined. The speed of pupil constriction was defined as the rate of pupil diameter change in response to illumination. Twenty-nine patients were included. Most were Chinese (26 of 29 [90%]) and female (18 of 29 [62%]). The anterior chamber area, angle opening distance at 500 μm from the scleral spur, and trabecular-iris space area at 500 μm from the scleral spur were significantly higher after LPI (P < .001). A significant increase was observed in the speed of pupil constriction after LPI (P < .005). In response to illumination, the rate of change in iris thickness at the sphincter muscle region and at 750 μm from the scleral spur was faster after LPI (P < .05). Similarly, an increase was observed in the speed of change of angle-opening distance at 500 μm from the scleral spur in response to illumination after LPI (P < .05). In patients with angle closure, changes in dynamic iridopupillary behavior are observed after LPI. The speed of pupillary constriction is faster after LPI.

Classification Algorithms Based on Anterior Segment Optical Coherence Tomography Measurements for Detection of Angle Closure

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. Cross-sectional study. We included 2047 subjects aged ≥50 years. 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. We assessed ASOCT measurements and angle closure. 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. 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. The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Quantitative evaluation of anterior chamber parameters using anterior segment optical coherence tomography in primary angle closure mechanisms

To evaluate different mechanisms of primary angle closure and to quantify anterior chamber parameters in these mechanisms using anterior segment optical coherence tomography in an Asian population. Hospital-based cross-sectional observational study. Forty-eight consecutive patients with primary angle closure glaucoma. Patients underwent complete ophthalmic examination and imaging of nasal-temporal angles with anterior segment optical coherence tomography. Images were categorized into four primary angle closure mechanisms: pupil block, plateau iris configuration, Thick peripheral iris roll and exaggerated lens vault. Parameters computed: anterior chamber depth central, anterior chamber depth at 1000 µm and 2000 µm anterior to scleral spur, lens vault, anterior chamber area, angle opening distance, trabecular iris space area and iris thickness. Anterior chamber parameters and primary angle closure mechanisms. Mean values of anterior chamber depths: central (P < 0.001), at 2000 µm (P < 0.001), 1000 µm (P < 0.001), lens vault (P < 0.001), anterior chamber area (P < 0.001), were significantly different among the four groups. Multivariate analysis showed anterior chamber depths: central, and anterior chamber depth at 2000 µm and anterior chamber area were higher in plateau iris and Thick peripheral iris roll and lower in exaggerated lens vault (P < 0.001) as compared to pupil block mechanism, lens vault was greater in exaggerated lens vault (P < 0.001) and lesser in plateau iris and Thick peripheral iris roll as compared to pupil block mechanism. Anterior segment optical coherence tomography may be used for evaluation of underlying primary angle closure mechanism(s) in a patient and tailor the treatment accordingly.

Ethnic Difference of the Anterior Chamber Area and Volume and Its Association with Angle Width

To compare the anterior chamber area/volume (ACA/ACV) and their relationship with the drainage angle between adult Caucasians and Chinese. Study groups were comprised of four age- and sex-matched cohorts: American Caucasians, American Chinese, southern mainland Chinese, and northern mainland Chinese. All subjects were consecutively recruited from general ophthalmology clinics except for southern mainland Chinese participants who were drawn from an ongoing population-based study. Anterior segment optical coherence tomography (ASOCT) images were obtained under dark conditions. Customized software was used to analyze structural indices including ACA/ACV, angle opening distance (AOD), anterior chamber depth (ACD), anterior chamber width (ACW), lens vault (LV), corneal arc depth (CAD), iris thickness (IT), iris curvature (ICurv), and iris area (IArea). Data from 121, 124, 121, and 120 participants were obtained of American Caucasians, American Chinese, and southern and northern mainland Chinese, respectively. After multiple linear regression analysis, adjusting for age, sex, pupil diameter (PD), and axial length (AL), ACA/ACV was positively associated with ACD, ACW, CAD, and corneal radius of curvature (CR) but negatively related with ICurv and IArea. Ethnic Chinese had significantly smaller ACA (β = -0.18, P = 0.022) and ACV (β = -3.9, P = 0.001) than Caucasians. ACV contributes the most to AOD variation for both Chinese (standardized regression coefficient [SRC] = 0.47, P < 0.001) and Caucasians (SRC = 0.59, P < 0.001). Compared with Caucasians, ethnic Chinese had smaller ACA/ACV independent of ACD, ACW, ICurv, IArea, PD, CR, and AL. ACA/ACV is the most prominent contributor to angle width variation for both Chinese and Caucasians in this study.

Factors Associated with Anterior Chamber Narrowing with Age: An Optical Coherence Tomography Study

The purpose of our study is to evaluate the effect of age on various anterior segment (AS) parameters in healthy eyes using AS optical coherence tomography (OCT), and to examine their relationship to anterior chamber angle (ACA) narrowing with age. A total of 388 consecutive Korean subjects aged 30 to 89 years was imaged by AS OCT. Anterior chamber depth (ACD), iris cross-sectional area (IA), iris thickness at 750 and 1500 μ from the scleral spur (IT(750, 1500)), iris curvature (IC), lens vault (LV), and anterior chamber area (AA) were determined using Image J software (version 1.44). The absolute and normalized slopes of these parameters, adjusted for axial length and sex, were determined by linear mixed-effects modeling. Multivariate regression analysis was performed to evaluate factors associated with ACA narrowing, which was defined as the angle-opening distance (AOD(500)) at the temporal angle. ACD and AA had significantly negative slopes (-0.0119 mm/year, -0.0845 mm(2)/year, P < 0.0001, <0.0001) with age, and LV, IC, IT(750), IT(1500), and IA had significantly positive slopes (0.0084 mm/year, 0.0019 mm/year, 0.0006 mm/year, 0.0008 mm/year, 0.0131 mm(2)/year, all P < 0.05). IC, ACD, LV, and AA underwent the greatest changes when analyzed by normalized slopes. IC, LV, age, and axial length were associated significantly with ACA narrowing (all P < 0.0001). Increments of LV, IC, IT, and IA with age led to a reduction in the dimensions of the AC and to narrowing of the ACA. This may explain why aging is a significant risk factor for primary angle closure glaucoma.

Changes in Anterior Segment Morphology after Laser Peripheral Iridotomy: An Anterior Segment Optical Coherence Tomography Study

Novel anterior segment optical coherence tomography (ASOCT) parameters associated with angle closure include anterior chamber area (ACA), anterior chamber volume (ACV), anterior chamber width (ACW), lens vault (LV), iris thickness (IT), iris area (I-area), and iris curvature (I-curv). We aimed to investigate changes in these parameters after laser peripheral iridotomy (LPI) in a cohort of primary angle-closure suspects (PACS). Prospective observational study. A total of 176 PACS aged ≥ 50 years who underwent LPI in 1 eye. We analyzed ASOCT images (Visante, Carl Zeiss Meditec, Dublin, CA) from all subjects using customized software before and 1 week after LPI. Multivariate linear regression analysis was performed for predictors of percentage change in mean angle opening distance (AOD750). Change in ASOCT parameters after LPI. The mean age of participants was 63 ± 7.3 years. The majority of subjects were Chinese (95.5%) and women (76.7%). Mean angle width (modified Shaffer grade) changed from 0.68 ± 0.54 at baseline to 1.76±0.69 after LPI (P<0.001) with a corresponding increase in mean AOD500 (0.12 vs. 0.19 mm, P<0.001), trabecular iris surface area (TISA500, 0.06 vs. 0.08 mm(2), P<0.001), and angle recess area (ARA, 0.13 vs. 0.17 mm(2), P<0.001). Mean ACA (15.0 vs. 16.0 mm(2), P<0.001) and ACV (91.6 vs. 103.0 mm(3), P<0.001) increased significantly after LPI, but there was no change in ACW, anterior chamber depth (ACD), or LV. Mean I-curv was reduced (0.375 vs. 0.18 mm, P<0.001) after LPI, but there was no significant change in IT or I-area. After multivariate analysis, mean LV (β = 0.286, P = 0.001), mean IT at 2000 μm (IT2000, β = 0.172, P = 0.034), and intraocular pressure (β = 0.159, P = 0.042) at baseline were found to be associated with ΔAOD750. This study confirms that LPI results in a significant increase in the angle width in PACS. The ACA and ACV increased after LPI, but there was no change in ACD, ACW, LV, IT, or I-area. The increase in ACA/ACV was mainly due to decreased I-curv after LPI.

Dynamic Changes in Anterior Segment (AS) Parameters in Eyes with Primary Angle Closure (PAC) and PAC Glaucoma and Open-Angle Eyes Assessed Using AS Optical Coherence Tomography

To evaluate serial changes in anterior segment (AS) parameters in terms of variation in pupil diameter (PD) using AS optical coherence tomography (OCT) in eyes with primary angle closure or primary angle closure glaucoma (PCG), age-matched open-angle (AO) eyes, and young open-angle (YO) eyes. Forty-four PCG (mean ± SD; 62.2 ± 7.5 years), 36 AO (62.0 ± 12.3 years), and 58 YO eyes (29.1 ± 7.0 years) were imaged under four standardized lighting conditions (3.25, 100.8, 426, and 1420 cd/m(2)). PD, anterior chamber depth (ACD), iris cross-sectional area (IA), iris thicknesses at 750 and 1500 μm from the scleral spur (IT750, IT1500), iris curvature (IC), lens vault (LV), and anterior chamber area (ACA), were calculated. The slope of the change in each AS parameter in terms of variation in PD was determined by a linear mixed-effect model. The mean ACD was significantly shallower (P < 0.001), the IC higher (P < 0.001), the IT750 greater (P = 0.026), the ACA smaller (P < 0.001), the LV greater (P < 0.001), and the IA wider (P = 0.019) in PCG eyes compared with AO eyes. However, the mean slope of no parameter differed significantly between PCG and AO eyes. The mean slopes of IC, IT1500, and IA differed between AO and YO eyes. Older eyes showed significantly different dynamic AS parameter responses in terms of change in PD compared with younger eyes. Thus, the authors suggest that changes in the dynamic features of AS parameters with age may contribute to angle closure development, in addition to any predisposing anatomic condition.