Guofu Huang

Anterior Chamber Depth, Iridocorneal Angle Width, and Intraocular Pressure Changes After Phacoemulsification: Narrow vs Open Iridocorneal Angles

OBJECTIVE To determine the association of changes in anterior chamber angle and anterior chamber depth (ACD) with intraocular pressure (IOP) reduction after uncomplicated phacoemulsification. METHODS In this prospective study, subjects underwent phacoemulsification with foldable lens implantation. Anterior chamber angle grading of 2 or less (Shaffer grading) in 3 or all quadrants was considered narrow angle (NA). Anterior segment optical coherence tomography and tonometry were performed preoperatively and 10 days and 1, 3, and 6 months after surgery. The ACD and angle opening distance at 500 μm anterior to the scleral spur (AOD500) were assessed from anterior segment optical coherence tomography. RESULTS Data were collected from 63 eyes that underwent cataract surgery. Twenty-six eyes were classified as having NA. Before surgery, the mean (SD) AOD500 and ACD in the NA group were 0.179 (0.014) mm and 2.23 (0.07) mm, respectively. Six months after surgery, the mean (SD) AOD500 and ACD in the NA group were 0.389 (0.025) mm and 3.75 (0.05) mm, respectively. The postoperative IOP was reduced significantly in both groups. We found that each 0.1-mm increase in AOD500 corresponded to a mean (SD) 0.42 (0.18)-mm Hg decrease in IOP (P < .001) in the NA group and 0.32 (0.16) mm Hg (P = .046) in the OA group. CONCLUSIONS Postoperative reduction in IOP was proportional to the increase in angle in both groups, but the IOP reduction per 0.1-mm increase in AOD500 in NA eyes was greater than that in OA eyes.

Association of biometric factors with anterior chamber angle widening and intraocular pressure reduction after uneventful phacoemulsification for cataract.

PURPOSE: To evaluate anterior chamber biometric factors associated with the degree of angle widening and intraocular pressure (IOP) reduction after phacoemulsification. SETTING: University of California, San Francisco, California, USA. DESIGN: Case series. METHODS: Anterior chamber parameters obtained by anterior segment coherence tomography were compared preoperatively and 3 months postoperatively. Measurements included the angle opening distance 500 μm anterior to the scleral spur (AOD500), trabecular–iris space area 500 μm from the scleral spur (TISA500), iris curvature (I‐Curv), anterior chamber angle (ACA), trabecular–iris space area, anterior chamber volume, anterior chamber width, and lens vault (LV). RESULTS: The study enrolled 73 eyes. The mean patient age was 77.45 years ± 7.84 (SD); 65.75% of patients were women. From preoperatively to 3 months postoperatively, the mean AOD500 increased significantly (0.254 ± 0.105 to 0.433 ± 0.108 mm) and the mean IOP decreased significantly (14.97 ± 3.35 to 12.62 ± 3.37 mm Hg) (P<.001). The reduction in IOP was correlated with the increase in AOD500 (r = 0.240, P=.041) and preoperative LV (r = 0.235, P=.045). After adjusting for related factors, AOD500 widening was positively correlated with LV (β = 0.458, P=.044) and I‐Curv (β = 0.235, P=.043) and negatively correlated with preoperative TISA500 (β = −0.269, P=.025) and ACA (β = −0.919, P=.027). CONCLUSIONS: Surgically induced AOD widening was significantly correlated with anterior chamber biometric factors. Preoperative LV appears to be a significant factor in angle widening and IOP reduction after phacoemulsification. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Heritability of Central Corneal Thickness in Chinese: The Guangzhou Twin Eye Study

PURPOSE To assess the heritability of central corneal thickness (CCT) in Chinese children in a classic twin study. METHODS Twins aged 8 to 16 years were recruited from the Guangzhou Twin Registry. Pachymetry data were obtained by one operator using the same imaging system. Zygosity was confirmed by genotyping with 16 polymorphic markers in all same-sex twin pairs. The CCT of the right eyes was chosen as the trait of interest in the analysis. Heritability was assessed by a general sex-limitation model, using Mx software (University of Richmond, Virginia). RESULTS Four hundred forty-nine twin pairs were available for data analyses, including 131 pairs of monozygotic boys (MZM), 44 pairs of dizygotic boys (DZM), 166 pairs of monozygotic girls (MZF), 31 pairs of dizygotic girls (DZF), and 77 pairs of opposite-sex dizygotic (OSDZ) twins. Twin correlations for CCT were 0.90 for MZM, 0.92 for MZF, 0.56 for DZM, 0.61 for DZF, and 0.44 for OSDZ twins. A sex-limitation model combining additive genetic and unique environmental factors produced the best fit for the data. Heritability estimates for CCT were 0.88 (95% confidence interval [CI]: 0.84-0.91) in the boys and 0.91 (95% CI: 0.89-0.93) in the girls. Unique environmental effects explained only 0.12 (95% CI: 0.09-0.16) and 0.09 (95% CI: 0.07-0.11) of the variance in CCT in the boys and the girls, respectively. CONCLUSIONS Additive genetic effects appear to be the major contributor to the variation of CCT in Chinese population. Heritability of CCT appears to be slightly greater in the girls than in the boys.

Association between Baseline Iris Thickness and Prophylactic Laser Peripheral Iridotomy Outcomes in Primary Angle-Closure Suspects

OBJECTIVE To evaluate the association between baseline measurements of iris thickness at 3 positions and change in anterior segment biometric parameters after prophylactic laser peripheral iridotomy (LPI). DESIGN Prospective clinical cohort study. PARTICIPANTS Fifty-two eyes of 52 nonglaucomatous subjects with anatomically narrow angles. METHODS Anterior segment optical coherence tomography (ASOCT) images captured before and after LPI were analyzed using customized software, the Zhongshan Angle Assessment Program (ZAAP) (Zhongshan Ophthalmic Centre, Guangzhou, China). Differences in preoperative and postoperative measurements for anterior segment biometric parameters were compared by paired Student t tests. Multivariate linear regression models, adjusted for age, sex, ethnicity, and preoperative pupil diameter, were used to examine the association between the baseline measurements of iris thickness at 3 positions and the change in anterior segment biometric parameters after LPI. MAIN OUTCOME MEASURES Baseline iris thickness measured at 750 μm from the scleral spur (IT750), iris thickness measured at 2000 μm from the scleral spur (IT2000), and maximal iris thickness (ITM). Changes in iris curvature (ICURV) and trabecular-iris space area at 500 μm from the scleral spur (TISA500) and 750 μm from the scleral spur (TISA750) after LPI. RESULTS The ICURV significantly decreased, whereas TISA500 and TISA750 significantly increased after LPI (all P < 0.0001). Lower baseline IT750 was significantly associated with greater postoperative increases in TISA500 and TISA750 (both P < 0.05). Lower baseline IT2000 and ITM were significantly associated with greater postoperative decrease in ICURV (both P < 0.05). CONCLUSIONS Our results showed that lower baseline measurements of iris thickness are associated with greater decrease in ICURV and increases in TISA500 and TISA750 after LPI. This suggests that eyes with thinner irides undergoing LPI were more likely to exhibit greater magnitude of change in terms of flattening of the iris convexity (i.e., ICURV) and widening of the anterior chamber angle (i.e., TISA500 and TISA750).

Distribution of central and peripheral corneal thickness in Chinese children and adults: the Guangzhou twin eye study.

Purpose: To describe the distribution of central and peripheral corneal thickness in children and adults by using a Scheimpflug camera. Methods: A total of 926 children 8-16 years of age and 662 adults 30-68 years of age were recruited from the Guangzhou Twin Registry. Central and peripheral corneal thicknesses were measured by using the Pentacam system with a standardized method. Regression analyses were used with the generalized estimating equation model, adjusting for the within-cluster correlation. Results: Corneal thicknesses, measured at the apex, center of pupil, superior, inferior, nasal, temporal peripheral, and the thinnest points, were 537.0 ± 29.4, 536.3 ± 29.3, 643.6 ± 37.2, 613.8 ± 32.4, 624.5 ± 35.0, 605.7 ± 33.4, and 533.2 ± 30.0 μm, respectively, in adults. In the children, these values were 550.7 ± 32.8, 550.7 ± 32.7, 656.0 ± 38.7, 627.9 ± 36.6, 642.1 ± 37.2, 612.5 ± 36.3, and 548.1 ± 32.8 μm, respectively. The thinnest point was located in the inferotemporal quadrant in 77.92% of children. All corneal thickness measurements showed no age-related change. Corneal thickness was generally thicker in boys than girls in the children, but this sex difference was not identified in adults. The discrepancy of measurements between the apex and thinnest point was small but statistically significant. Conclusions: Central and 3.0-mm peripheral corneal thicknesses were normally distributed. No age-related differences were shown. A sex difference was shown in children but not in adults. Understanding the discrepancy between the apex and thinnest point could be useful in the safe management of refractive surgery.

Differences in Iris Thickness Among African Americans, Caucasian Americans, Hispanic Americans, Chinese Americans, and Filipino-Americans

Purpose:To evaluate the capability of iris thickness parameters to explain the difference in primary angle-closure glaucoma prevalence among the different racial groups. Methods:In this prospective study, 436 patients with open and narrow angles that met inclusion criteria were consecutively recruited from the UCSF general ophthalmology and glaucoma clinics to receive anterior segment optical coherence tomography imaging under standardized dark conditions. Images from 11 patients were removed due to poor visibility of the scleral spurs and the remaining images were analyzed using the Zhongshan Angle Assessment Program to assess the following measurements for the nasal and temporal angle of the anterior chamber: iris thickness at 750 and 2000 &mgr;m from the scleral spurs and the maximum iris thickness at middle one third of the iris. Iris thickness parameters were compared among and within the following 5 different racial groups: African Americans, Caucasian Americans, Hispanic Americans, Chinese Americans, and Filipino-Americans. Results:In comparing iris parameters among the open-angle racial groups, significant differences were found for nasal iris thickness at 750 and 2000 &mgr;m from the scleral spurs in which Chinese Americans displayed the highest mean value (P=0.01, P<0.0001). Among the narrow-angle racial groups, significant difference was found for nasal iris thickness at 2000 &mgr;m from the scleral in which Chinese Americans showed the highest mean value (P<0.0001). Significant difference was also found for temporal maximum iris thickness at middle one third of the iris in which African Americans exhibited the highest mean value (P=0.021). Iris thickness was modeled as a function of angle status using linear mixed-effects regression, adjusting for age, sex, pupil diameter, spherical equivalent, ethnicity, and the use of both eyes in patients. The iris thickness difference between the narrow-angle and open-angle groups was significant (P=0.0007). Conclusions:Racial groups that historically showed higher prevalence of primary angle-closure glaucoma possess thicker irides.

Compliance with follow-up after cataract surgery in rural China.

Purpose: To evaluate reasons for non-compliance with post-cataract surgical follow-up in rural China, and assess the impact of incentives on improving compliance. Methods: Patients having undergone cataract surgery more than 3 months previously at cataract surgery training hospitals in Guangdong were invited by telephone and advertisements to a hospital-based study examination, with compensation for travel costs (US

Anatomic Predictors for Anterior Chamber Angle Opening After Laser Peripheral Iridotomy in Narrow Angle Eyes

7). Information on prior post-surgical follow up was collected by questionnaire at the hospital or by telephone. Logistic regression was used to assess predictors of post-operative attendance with or without compensation. Results: Among 518 eligible patients, 426 (82.2%) underwent interviews and 342 (66.0%) attended the compensated study examination. Ninety nine participants (23.2%) reported previously returning for uncompensated follow-up ≥ 3 months post-operatively, and 225 (52.8%) had returned for any prior post-operative examination. Uncompensated follow-up at ≥ 3 months was associated with higher income (P = 0.037), and recalling instruction by a doctor to follow-up (P = 0.001), while age, gender, travel cost, and post-operative satisfaction and vision were not associated. Younger (P = 0.002) patients and those reporting being instructed to follow up (P = 0.008) were more likely to return for the compensated research examination. Among all interviewed subjects, only 170 (39.9%) reported knowing they were to return to hospital. Conclusions: Modest compensation, advertisements and telephone contact can increase medium-term follow-up rates after cataract surgery by three-fold. Better communication of specific targets for follow-up may improve follow-up compliance.

Comparison of anterior ocular segment biometry features and related factors among American Caucasians, American Chinese and mainland Chinese

Purpose: To investigate anterior chamber parameters and biometric factors associated with degree of angle opening after laser peripheral iridotomy (LPI) for narrow angles. Methods: In this prospective cohort study, patients with narrow angles who were scheduled for LPI were recruited. Anterior chamber parameters by anterior segment coherence tomography (ASOCT) under dark conditions were compared before and after LPI. Only the right eye was used for analysis if both eyes were eligible. Measurements performed by customized software included anterior chamber depth, iris area, angle opening distance at 500 µm (AOD500) anterior to the scleral spur, iris thickness at 750 µm from sclera spur (IT750), trabecular-iris space area 500 (TISA500), and iris curvature (I-Curv). Univariate and multiple regression analyses were performed to determine the predictive factors of angle opening after LPI. Results: Eighty-one patients with narrow angles were prospectively recruited in this study. The AOD500 increased significantly from 0.128 ± 0.081 mm (before) to 0.209 ± 0.087 mm (after) in the nasal quadrant, and from 0.103 ± 0.067 mm (before) to 0.197 ± 0.071 mm (after) in the temporal quadrant (p < 0.001 for both nasal and temporal). I-Curv decreased significantly after LPI (p < 0.001). Significant increase was noted in TISA500 before and after LPI (p < 0.001). In the multiple regression model, increase in AOD500 was positively correlated with age (standardized β = 0.283, p = 0.007) and I-Curv (standardized β = 0.239, p = 0.021), and was negatively correlated with preoperative iris area (standardized β = −0.292, p = 0.015). Conclusions: In this hospital-based study on the results of LPI for narrow angle subjects, statistically significant independent predictors of anterior chamber angle widening after LPI were older age, smaller iris area, and steeper iris.

Outcomes of Cataract Surgery in Urban Southern China: The Liwan Eye Study

Background:  To compare the anterior segment biometric parameters amongst adult American Caucasians, American Chinese and mainland Chinese, in order to determine parameters that may contribute to increased risk for angle closure in Chinese.