Iris Cross-sectional Area Research Articles

Associations of static and dynamic iris parameters in healthy Chinese individuals: the Handan Eye Study.

To determine the associations between the demographic factors (age and sex) and physiological dynamic iris changes and explore the associated factors for iris cross-sectional area (IA) change in healthy Chinese individuals. This cross-sectional study included individuals aged ≥40 years with an open angle and underwent anterior segment optical coherence tomography under light and dark conditions from the follow-up cohort of the Handan Eye Study. Ocular data from the right eye were analyzed. The Pearson correlation coefficient was used to assess the relationship between age and iris parameters, including iris thickness (IT), IA, and iris curvature (IC), as well as the pupil diameter (PD) in the dark, and their changes from light to dark conditions. Linear regression analysis was performed to identify the potential factors associated with IA change. The final analysis included 465 healthy individuals. PD in dark, IA change and PD change decreased with age (P < 0.001), whereas IC increased with age (P < 0.001). IT and IT change were smaller, and IC was larger in women than that in men (P = 0.021, 0.007, and 0.010, respectively). Older age (P = 0.041), larger lens thickness (P = 0.013), larger IC change (P < 0.001), and smaller PD change (P < 0.001) were significantly associated with a smaller IA change. Our study demonstrated the associations of static and dynamic iris parameters in healthy Chinese individuals. The findings provided a possible explanation for the higher prevalence of primary angle closure disease in elderly and female populations.

Quantitative analysis of dynamic iris changes in primary angle-closure disease with long axial lengths: the Handan Eye Study.

To investigate dynamic iris changes in patients with primary angle-closure disease (PACD) with long axial length (AL) compared to those with short and medium AL. This observational cross-sectional study enrolled participants aged 35 years or older from the Handan Eye Study follow-up examination who were diagnosed with PACD and underwent Visante anterior segment optical coherence tomography (ASOCT) imaging under light and dark conditions. The right eye of each participant was included in the analysis. AL was categorized as short (<22.0 mm), medium (≥22.0 to ≤23.5 mm), or long (>23.5 mm). Anterior segment parameters, including iris dynamic changes, were compared among the three groups with different ALs. Data from 448 patients with PACD were analyzed. We found that 10.9% of included eyes had a long AL with a flatter cornea; larger central anterior chamber depth, angle opening distance, anterior chamber width, anterior chamber area, and volume; and smaller lens thickness and lens vault (LV) (P < 0.05) than those with short AL. No significant difference existed between the three groups in iris thickness, iris cross-sectional area (IA), iris curvature, or pupil diameter (PD) change between light and dark (P > 0.05). The significant associated factors for IA changes were area recess area (ARA) in the dark, LV in the dark, and PD change from light to dark (P < 0.05). Dynamic and static iris parameters were consistent across patients with PACD with short, medium, or long AL and may contribute to the pathogenesis of angle closure in atypical PACD.

Comparative Study of the Effects of 1% Atropine on the Anterior Segment.

Purpose To investigate the influences of atropine on changes in anterior segment geometry, as measured by ultrasound biomicroscopy in children. Methods A prospective observational study was performed. Anterior segment parameters were obtained by UBM before and after the instillation of 1% atropine. Univariate linear regression was performed to identify the variables contributing to the changes in the trabecular meshwork-iris angle (TIA). Results The study included 21 boys and 37 girls with a mean age of 10.79 ± 2.53 years. Anterior chamber parameters including the central anterior chamber depth, TIA, angle opening distance at 500 μm from the scleral spur, iris thickness 750 μm and 1500 μm from the scleral spur, trabecular-ciliary angle (TCA), trabecular-ciliary process distance, sclera-iris angle (SIA), and sclera-ciliary process angle significantly increased after cycloplegia (P < 0.05). In contrast, the lens vault, iris cross-sectional area, and maximum ciliary muscle thickness significantly decreased after cycloplegia. Univariate analysis identified the change in TCA and the change in SIA and the TIA before mydriasis as determinants of the change in TIA. Conclusions Atropine causes statistically significant changes in various anterior segment parameters in children. The change in anterior chamber angle is associated with the change in TCA and the change in SIA and the TIA before mydriasis.

Establishment and Comparison of Algorithms for Detection of Primary Angle Closure Suspect Based on Static and Dynamic Anterior Segment Parameters.

PurposeTo establish and evaluate algorithms for detection of primary angle closure suspects (PACS), the risk factor for primary angle closure disease by combining multiple static and dynamic anterior segment optical coherence tomography (ASOCT) parameters.MethodsObservational, cross-sectional study. The right eyes of subjects aged ≥40 years who participated in the 5-year follow-up of the Handan Eye Study, and underwent gonioscopy and ASOCT examinations under light and dark conditions were included. All ASOCT images were analyzed by Zhongshan Angle Assessment Program. Backward logistic regression (BLR) was used for inclusion of variables in the prediction models. BLR, naïve Bayes’ classification (NBC), and neural network (NN) were evaluated and compared using the area under the receiver operating characteristic curve (AUC).ResultsData from 744 subjects (405 eyes with PACS and 339 normal eyes) were analyzed. Angle recess area at 750 µm, anterior chamber volume, lens vault in light and iris cross-sectional area change/pupil diameter change were included in the prediction models. The AUCs of BLR, NBC, and NN were 0.827 (95% confidence interval [CI], 0.798-0.856), 0.826 (95% CI, 0.797-0.854), and 0.844 (95% CI, 0.817-0.871), respectively. No significant statistical differences were found between the three algorithms (P = 0.622).ConclusionsThe three algorithms did not meet the requirements for population-based screening of PACS. One possible reason could be the different angle closure mechanisms in enrolled eyes.Translational RelevanceThis study provides a promise for basis for future research directed toward the development of an image-based, noncontact method to screen for angle closure.

Subclassification of Primary Angle Closure Using Anterior Segment Optical Coherence Tomography and Ultrasound Biomicroscopic Parameters

To classify eyes with primary angle closure (PAC) in terms of the features visualized using anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM). Retrospective, observational study. A total of 73 eyes of 73 patients with PAC. Participants' eyes that had undergone laser peripheral iridotomy (LPI) were imaged using AS-OCT and UBM under the same lighting conditions. Anterior chamber depth, anterior chamber width, iris cross-sectional area, peripheral iris thickness, iris curvature, lens vault (LV), and angle opening distance 500 μm from the scleral spur (SS) were determined using the AS-OCT image; trabecular-ciliary process angle (TCA), trabecular-ciliary process distance (TCPD), and ciliary body (CB) thickness 1 mm posterior to the SS were estimated on the UBM image using ImageJ software (Wayne Rasband, National Institutes of Health, Rockville, MD). Iris insertion, iris angulation, iris convexity, presence of ciliary sulcus, irido-angle contact, and CB orientation assessed on the UBM image were included. Partitioning around the medoids algorithm was used for cluster analysis based on the parameters obtained using AS-OCT and UBM. Axial length and pupil diameter were incorporated into statistical models. Clinical and anatomic characteristics were compared between the clusters, as classified using the partitioning around medoids algorithm method. Cluster analysis revealed that 2-group clustering produced the best results. The 2 clusters, which were defined in terms of parameters obtained using AS-OCT and UBM, showed differences in iris curvature (0.16±0.08 vs. 0.11±0.04 mm), TCA (91.0°±13.4° vs. 63.7°±6.2°), TCPD (0.99±0.22 vs. 0.78±0.16 mm), CB orientation (neutral/anterior, 35/13 vs. 0/25), and iris insertion (basal/middle/apical, 37/9/2 vs. 12/11/2). Pre-LPI intraocular pressure (IOP) (18.8±5.4 vs. 16.2±4.5 mmHg; P= 0.037) and percentage of IOP reduction after LPI (22.3%±17.9% vs. 8.3%±19.5%; P < 0.003) showed a significant difference between the 2 clusters. The most distinct difference between the 2 subgroups in the cluster analysis was TCA, suggesting that the position of the CB is important in subclassifying PAC. By using UBM, clinicians may obtain more clues about the mechanisms of PAC; in turn, they may learn to predict the IOP-lowering effects of LPI.

Cross-sectional, observational study of anterior segment parameters using anterior segment optical coherence tomography in North Indian Population.

Purpose:To study the anterior segment (AS) parameters using AS optical coherence tomography (AS-OCT) in the North Indian population.Methods:A hospital-based, observational, cross-sectional study was conducted over a period of 1 year. It included 251 normal individuals aged 20–70 years. Participants underwent imaging with AS-OCT. Ocular parameters included anterior chamber angle (ACA), iris cross-sectional area (ICSA), iris thickness (IT), and iris curvature (IC). The parameters were measured nasally and temporally for both sexes and different age groups.Results:The mean age of participants was 48.3 ± 13.9 years and 50.6% were men. The ACA decreased with age whereas ICSA, IT, and IC increased with age. The ACA (P = 0.0001nasally and temporally), ICSA (P = 0.011 nasally, P = 0.027 temporally), IT750 (P = 0.001 nasally, P = 0.011 temporally), IT1500 (P = 0.002 nasally, P = 0.002 temporally), and IC (P = 0.059 nasally, P = 0.128 temporally) underwent statistically significant changes with increasing age. No significant difference was seen in parameters of different sex.Conclusion:In this subset of the Indian population, the change in the AC parameters with age influences the AC dimensions predisposing the eye to glaucomatous conditions. These data are applicable clinically for the assessment and surgical management of patients requiring AS surgery.

Establishing Age-Adjusted Reference Ranges for Iris-Related Parameters in Open Angle Eyes with Anterior Segment Optical Coherence Tomography.

PurposeDefine criteria for iris-related parameters in an adult open angle population as measured with swept source Fourier domain anterior segment optical coherence tomography (ASOCT).MethodsNinety-eight eyes of 98 participants with open angles were included and stratified into 5 age groups (18–35, 36–45, 46–55, 56–65, and 66–79 years). ASOCT scans with 3D mode angle analysis were taken with the CASIA SS-1000 (Tomey Corporation, Nagoya, Japan) and analyzed using the Anterior Chamber Analysis and Interpretation software. Anterior iris surface length (AISL), length of scleral spur landmark (SSL) to pupillary margin (SSL-to-PM), iris contour ratio (ICR = AISL/SSL-to-PM), pupil radius, radius of iris centroid (RICe), and iris volume were measured. Outcome variables were summarized for all eyes and age groups, and mean values among age groups were compared using one-way analysis of variance. Stepwise regression analysis was used to investigate demographic and ocular characteristic factors that affected each iris-related parameter.ResultsMean (±SD) values were 2.24 mm (±0.46), 4.06 mm (±0.27), 3.65 mm (±0.48), 4.16 mm (±0.47), 1.14 (±0.04), 1.51 mm2 (±0.23), and 38.42 μL (±4.91) for pupillary radius, RICe, SSL-to-PM, AISL, ICR, iris cross-sectional area, and iris volume, respectively. Both pupillary radius (P = 0.002) and RICe (P = 0.027) decreased with age, while SSL-to-PM (P = 0.002) and AISL increased with age (P = 0.001). ICR (P = 0.54) and iris volume (P = 0.49) were not affected by age.ConclusionThis study establishes reference values for iris-related parameters in an adult open angle population, which will be useful for future studies examining the role of iris changes in pathologic states.

Dynamic Iris Changes as a Risk Factor in Primary Angle Closure Disease.

We studied the association between dynamic iris changes and the spectrum of primary angle closure disease (PACD), using the anterior segment optical coherence tomography (ASOCT). Eligible primary angle closure (PAC), primary angle closure glaucoma (PACG), age, and sex comparable primary angle closure suspects (PACS) and normal subjects from the 5-year follow-up of the Handan Eye Study underwent ASOCT testing in dark and light conditions. The right eye of each subject was analyzed and biometric parameters including iris cross-sectional area (IA), lens vault (LV), pupil diameter (PD), and centroid-to-centroid distance (CCD) were calculated using the Zhongshan Angle Assessment Program. Totals of 31 PACS, 31 PAC/PACG, and 31 normal eyes were eligible for analysis. Loss of IA per mm PD increase in the dark compared to light was 0.18 mm in PACS, 0.13 mm in PAC/PACG, and 0.24 mm in normal (P = 0.015 between groups) groups. Diagnoses of normal (P = 0.001) and a smaller PD in light (P = 0.003) were statistically significant determinants of a larger IA loss per mm PD increase in the dark compared to light. Logistic regression analysis showed that LV (P = 0.002) and IA loss per mm PD increase (P = 0.017) were risk factors for an occludable angle. Significant differences in iris behavior in the dark compared to light in PACS, PACD, and normal eyes add to the evidence that dynamic iris change has a role in the pathogenesis of PAC in a rural Chinese population.

Anterior segment changes after pharmacologic mydriasis using Pentacam and optical coherence tomography in angle closure suspects.

To compare the dynamic changes of anterior segment parameters especially iris morphology induced by pharmacologic mydriasis between angle closure suspects and normal controls. The study group comprised 19 eyes of 19 angle closure suspects and 19 eyes of 19 age- and sex-matched normal open-angle eyes. Pentacam and optical coherence tomography measurements before and 30min after instillation of compound tropicamide eye drop were performed and compared. Biometric evaluations of iris tomography and anterior chamber angle were estimated by a customized image-processing software. Baseline axial length, iris cross sectional area and volume did not differ significantly between angle closure suspects and normal controls. Angle closure suspects had smaller pupil size, narrower anterior segment dimension and axial length, thinner iris with greater curve in comparison with normal controls. Pharmacologic mydriasis led to significant increments in iris thickness at 750 µm, anterior chamber depth and volume, whereas significant decrements in iris curve, cross sectional area and volume in both groups. Angle opening distance at 500 µm was increased significantly in normal controls (from 0.465±0.115 mm to 0.539±0.167 mm, P=0.009), but not in angle closure suspects (from 0.125±0.100 mm to 0.145±0.131 mm, P=0.326). Iris volume change per millimeter of pupil dilation (ΔIV/ΔPD) decreased significantly less in angle closure suspects than normal controls (-2.47±1.33 mm(2) vs -3.63±1.58 mm(2), P=0.019). Linear regression analysis showed that the change of angle opening distance at 500 µm was associated most with the change of central anterior chamber depth (β=0.841, P=0.002) and ΔIV/ΔPD (β=0.028, P=0.002), followed by gender (β=0.062, P=0.032). Smaller iris volume decrement per millimeter of pupil dilation is related significantly with the less anterior angle opening in angle closure suspects after pharmacologic mydriasis. Dynamic iris change may be as a prospective indicator of iris compressibility and angle closure glaucoma.

Quantitative analysis of iris changes after physiologic and pharmacologic mydriasis in a rural Chinese population.

To estimate and compare the change in iris cross-sectional area (IA) and iris volume (IV) following physiologic and pharmacologic pupil dilation in primary angle closure suspects (PACS) and normal subjects. Anterior segment-optical coherence tomography (AS-OCT) measurements in light, dark, and following pharmacologic dilation were obtained on 186 PACS and 224 normal subjects examined during the 5-year follow-up of the Handan Eye Study. Iris cross-sectional area, IV, and other biometric parameters calculated using the Zhongshan angle assessment program in the right eyes of all subjects were analyzed. The mean IA and IV decreased in dark compared with light and after pharmacologic dilation in both PACS and normal eyes. This change was statistically significant in normal eyes: light versus pharmacologic dilation for IA (P = 0.038) and for IV, both light versus dark (P = 0.031) and light versus pharmacologic dilation (P = 0.012). A longer axial length (P = 0.028) and a greater change in pupil diameter (PD) (P < 0.001) were associated with a larger decrease of IA for the light to dark comparison. A diagnosis of normal eyes (P = 0.011), larger PD in dark (P = 0.001), and a larger change in PD (P = 0.001) were associated with a larger decrease of IV from light to dark. The differences in iris behavior between PACS and normal rural Chinese subjects following physiologic or pharmacologic pupillary dilation may help provide insights into the pathogenesis of angle closure.

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.

Variations in Iris Volume with Physiologic Mydriasis in Subtypes of Primary Angle Closure Glaucoma

To compare the changes in iris volume with pupil dilation using anterior segment optical coherence tomography (AS-OCT) in eyes of subjects with different subtypes of primary angle closure. This prospective study examined 44 fellow eyes (FA group) of subjects with previous acute primary angle closure (APAC), and 56 subjects (AC group) with chronic primary angle closure and/or primary angle closure glaucoma. All participants underwent gonioscopy and AS-OCT imaging. The iris volume, iris cross-sectional area, and pupil diameter were measured with custom semiautomated software. The main outcome variable analyzed was mean change in iris volume between light and dark conditions in a multivariate linear regression analysis. Thirty-five eyes from the FA group (79.5%) and 50 eyes from the AC group (89.3%) were included in the final analysis. When going from light to dark, iris volume did not change significantly in eyes in the FA group (+1.50 ± 6.73 mm(3); P = 0.19), but decreased in the AC group by 1.52 ± 3.07 mm(3) (P < 0.001). This difference was significant (P = 0.01). On multivariate analysis after controlling for age, sex, baseline pupil diameter, and change in pupil diameter, age (β = -0.397; P < 0.001) and diagnostic category (AC versus FA group; β = 0.347; P < 0.001) were significant determinants of iris volume change. With physiologic mydriasis, the iris volume decreased in eyes with chronic angle closure but remained unchanged in fellow eyes of APAC. Such variations in iris volume responses may influence the subtype of angle closure that develops.

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.

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.

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.

Preoperative iris configuration and intraocular pressure after cataract surgery

To determine predictors of long-term intraocular pressure (IOP) after cataract surgery. Hunter Holmes McGuire Veterans Administration Hospital, Richmond, Virginia, USA. Case series. Clinical variables, IOP by applanation tonometry, anatomic features on anterior segment optical coherence tomography (AS-OCT), and gonioscopy were assessed before and after uneventful cataract surgery in eyes with open filtration angles. Multivariate linear regression of preoperative measurements was used to predict the mean IOP from 2 to 18 months postoperatively. The study enrolled 77 eyes (77 patients). Prediction of the mean postoperative IOP improved when up to 4 preoperative IOP values were averaged (r(2) = 0.20) compared with using the final preoperative IOP value only (r(2) = 0.13). The mean iris cross-sectional area decreased after surgery, from 3.84 mm(2) to 3.70 mm(2) (P=.01). The mean convex hull of the iris segments also decreased, from 5.05 mm(2) to 4.19 mm(2) (P<.001). The mean postoperative IOP was independently predicted by the preoperative average IOP, primary open-angle glaucoma, and the convex hull of cross-sectional iris segments (P=.001, model r(2) = 0.38) or iris cross-sectional area (P=.003, model r(2) = 0.36). Phacoemulsification parameters, incision type, and anterior chamber angle and depth did not predict postoperative IOP. Averaging up to 4 preoperative IOP values improved postoperative IOP predictions. A high iris cross-sectional area or convex hull of the iris segments on AS-OCT was associated with lower postoperative IOP. These findings might help identify patients who are likely to have the largest IOP drop after cataract surgery.

Pigment Dispersion Syndrome Patients Do Not Have Larger-than-normal Irides

To compare iris cross-sectional area and thickness in the accommodated and unaccommodated states in controls versus patients with pigment dispersion syndrome (PDS) and to quantify short-term response of the iris to accommodation. Thirty-three patients with PDS and 17 control subjects were examined with ultrasound biomicroscopy. A radial image of the iris and ciliary body was taken at the temporal quadrant before and after accommodation with the patient looking at a standardized target. Iris thickness was measured from a line perpendicular to the iris from points on the trabecular meshwork 500, 1000, and 3000 μm from the scleral spur. Ciliary body thickness was measured 500 μm posterior to the scleral spur. Independent sample t tests (2-sided) compared iris thickness and cross-sectional area between groups. All participants were of European descent. Mean age was 45.6 ± 5.4 years (mean ± 95% confidence interval) in the PDS group and 34.9 ± 5.5 in the controls. Mean refractive error was -4.26 ± 1.0 diopters in the PDS group and -4.83 ± 1.0 diopters in the controls (P=0.499). There was no significant difference in iris cross-sectional area in the accommodated and unaccommodated states between the 3 groups. For all quantities measured (iris thickness at 500, 1000, 3000 μm; iris cross-sectional area; ciliary body thickness and area), there was no significant difference between the control group and the PDS group (P>0.35). Iris cross-sectional area and thickness and ciliary body thickness were similar in the accommodated and unaccommodated states in PDS and controls. This result provides further suggestive evidence that nongeometrical factors contribute to the development of PDS.

Iris Cross-sectional Area Decreases With Pupil Dilation and its Dynamic Behavior is a Risk Factor in Angle Closure

To estimate the change in iris cross-sectional (CS) area with pupil dilation using anterior segment optical coherence tomography comparing eyes with angle closure (AC) to open angle glaucoma (OAG). Sixty-five patients from the Wilmer Glaucoma service, 36 with definite or suspected OAG and 29 with definite or suspected AC, underwent anterior segment optical coherence tomography imaging under 3 conditions (pupil constriction to light, physiologic dilation in the dark, and after pharmacologic dilation). The nasal and temporal iris CS areas were measured with custom software, 3 times in each of 4 meridians. The principal outcome variables were iris CS area and change in iris CS area/mm pupil diameter change. The relation of these parameters to potential variables that would influence iris area was estimated by multivariate regression. CS area was smaller in eyes with larger pupil diameter, those that had undergone trabeculectomy, and those of European-derived persons (P<0.05 for all in a univariate analysis). In a multivariate model with CS area as the dependent variable, larger pupil diameter (with a 0.19 mm decrease in CS area for each 1 mm of pupil enlargement, P=0.0002), and trabeculectomy remained significant factors. In a second multivariate model, AC irides had less change in CS area/mm pupil enlargement than OAG or OAG suspects (P=0.01). Change in iris CS area was essentially complete in 5 seconds (n=10 eyes). The iris loses nearly half its volume from a pupil diameter of 3 to 7 mm, probably by eliminating extracellular fluid. Smaller iris CS area change with physiologic pupil dilation is a potential risk factor for AC. Dynamic iris CS area change deserves testing as a prospective indicator of AC.