Screening techniques for angle-closure glaucoma in rural Taiwan

Performance of anterior segment OCT-based algorithms in the opportunistic screening for primary angle-closure disease

Purpose

This study aimed to investigate the performance of deep learning algorithms in the opportunistic screening for primary angle-closure disease (PACD) using combined anterior segment parameters.

Methods

This was an observational, cross-sectional hospital-based study. Patients with PACD and healthy controls who underwent comprehensive eye examinations, including gonioscopy and anterior segment optical coherence tomography (ASOCT) examinations under both light and dark conditions, were consecutively enrolled from the Department of Ophthalmology at the Beijing Tongren Hospital between November 2020 and June 2022. The anterior chamber, anterior chamber angle, iris, and lens parameters were assessed using ASOCT. To build the prediction models, backward logistic regression was utilized to select the variables to discriminate patients with PACD from normal participants, and the area under the receiver operating characteristic curve was used to evaluate the efficacy of the opportunistic screening.

Results

The data from 199 patients (199 eyes) were included in the final analysis and divided into two groups: PACD (109 eyes) and controls (90 eyes). Angle opening distance at 500 μm, anterior chamber area, and iris curvature measured in the light condition were included in the final prediction models. The area under the receiver operating characteristic curve was 0.968, with a sensitivity of 91.74 % and a specificity of 91.11 %.

Conclusion

ASOCT-based algorithms showed excellent diagnostic performance in the opportunistic screening for PACD. These results provide a promising basis for future research on the development of an angle-closure probability scoring system for PACD screening.

Can ultrasonic biometric indices with optimal cut-offs be a potential screening tool for primary angle closure disease? A case-control study

BACKGROUND/OBJECTIVES

Despite a significant disease burden and potential to cause blindness, primary angle closure disease (PACD) does not have a population-based screening programme. Biometric indices using ultrasound A-scan is a potential tool for glaucoma case-detection. Given that genetic and environmental factors influence these parameters and paucity of data on their discrimination thresholds in Indian populace, we conducted a matched case-control study to determine the biometric indices and their discrimination thresholds associated with PACD.

METHODS

We studied 172 eyes of 86 participants (43 cases; 43 controls). We compared the following biometric parameters of cases (PACD, occludable angle ≥180° ± raised intraocular pressure) with age and gender-matched controls (1:1): Anterior chamber depth (ACD), lens thickness (LT), axial length (AXL), lens position (LP), relative lens position (RLP), lens axial factor (LAF), simple crowding value (Cs), ACD/AXL). We performed conditional logistic regression (to identify factors associated with PACD) and Receiver operating characteristic (ROC) analysis (to determine discrimination thresholds).

RESULTS

Reduced ACD (Adj OR 0.01; 95% CI: 0.0003-0.15, p < 0.001) and increased LT (Adj OR 10.3; 95% CI:2.42-43.93, p < 0.001) were associated with PACD. On ROC analysis, ACD, Cs, and ACD/AXL had optimum sensitivity/specificity at ≤3.015, ≥0.056 and ≤0.1303, respectively. ACD (88.4%) and Cs (94.2%) had highest sensitivity and specificity, respectively.

CONCLUSION

Ultrasonic biometric parameters differed significantly between PACD and controls. ACD and Cs (at discrimination thresholds of ≤3.015 mm and ≥ 0.056, respectively) using ultrasound A-scan could be a potential tool for PACD case-detection that requires evaluation of its diagnostic yield and cost-effectiveness.

From 2 dimensions to 3rd dimension: Quantitative prediction of anterior chamber depth from anterior segment photographs via deep-learning

Anterior chamber depth (ACD) is a major risk factor of angle closure disease, and has been used in angle closure screening in various populations. However, ACD is measured from ocular biometer or anterior segment optical coherence tomography (AS-OCT), which are costly and may not be readily available in primary care and community settings. Thus, this proof-of-concept study aims to predict ACD from low-cost anterior segment photographs (ASPs) using deep-learning (DL). We included 2,311 pairs of ASPs and ACD measurements for algorithm development and validation, and 380 pairs for algorithm testing. We captured ASPs with a digital camera mounted on a slit-lamp biomicroscope. Anterior chamber depth was measured with ocular biometer (IOLMaster700 or Lenstar LS9000) in data used for algorithm development and validation, and with AS-OCT (Visante) in data used for testing. The DL algorithm was modified from the ResNet-50 architecture, and assessed using mean absolute error (MAE), coefficient-of-determination (R2), Bland-Altman plot and intraclass correlation coefficients (ICC). In validation, our algorithm predicted ACD with a MAE (standard deviation) of 0.18 (0.14) mm; R2 = 0.63. The MAE of predicted ACD was 0.18 (0.14) mm in eyes with open angles and 0.19 (0.14) mm in eyes with angle closure. The ICC between actual and predicted ACD measurements was 0.81 (95% CI 0.77, 0.84). In testing, our algorithm predicted ACD with a MAE of 0.23 (0.18) mm; R2 = 0.37. Saliency maps highlighted the pupil and its margin as the main structures used in ACD prediction. This study demonstrates the possibility of predicting ACD from ASPs via DL. This algorithm mimics an ocular biometer in making its prediction, and provides a foundation to predict other quantitative measurements that are relevant to angle closure screening.

New loci for refractive errors and ocular biometric parameters in young Chinese Han adults

Myopia has become a major public health issue with an increasing prevalence. There are still individuals who experience similar environmental risk factors and, yet, remain non-myopic. Thus, there might be genetic factors protecting people from myopia. Considering the opposite ocular characteristics of primary angle closure glaucoma (PACG) to myopia and possible common pathway between them, we propose that certain risk genes for PACG might act as a protective factor for myopia. In this study, 2,678 young adults were genotyped for 37 targeted single nucleotide polymorphisms. Compared with emmetropia, rs1401999 (allele C: OR=0.795, P=0.03; genotype in dominant model: OR=0.759, P=0.02) and rs1258267 (allele A: OR=0.824, P=0.03; genotype in dominant model: OR=0.603, P=0.01) were associated with low to moderate myopia and high myopia, respectively. Genotype under recessive model of rs11024102 was correlated with myopia (OR=1.456, P=0.01), low to moderate myopia (OR=1.443, P=0.02) and high myopia (OR=1.453, P=0.02). However, these associations did not survive Bonferroni correction. Moreover, rs1401999, rs1258267, and rs11024102 showed associations with certain ocular biometric parameters in different groups. Our study suggests that ABCC5, CHAT and PLEKHA7 might be associated with refractive errors by contributing to the regulation of ocular biometry, in terms of uncorrected results and their biological functions.

Evaluation of the Diagnostic Performance of Swept-Source Anterior Segment Optical Coherence Tomography in Primary Angle Closure Disease

PURPOSE

To evaluate the diagnostic performance of swept-source anterior segment optical coherence tomography (SS-OCT) in differentiating eyes with primary angle closure disease (PACD) from eyes of control subjects, as well as eyes with PAC and PAC glaucoma (PACG) from eyes with PAC suspect (PACS) disease.

DESIGN

Multicenter cross-sectional study.

METHODS

Chinese patients were classified into control, PACS, and PAC/PACG groups. The area under the receiving operating characteristic curve (AUC) from logistic regression models was used to evaluate discriminating ability. Sensitivity and specificity were calculated, and performance of the models was validated using an independent dataset.

RESULTS

A total of 2928 SS-OCT images from 366 eyes of 260 patients were recruited to develop diagnostic models. The validation dataset included 1176 SS-OCT images from 147 eyes of 143 patients. For distinguishing PACD from control eyes, average anterior chamber depth had the highest AUC (0.94). With a cutoff of 2.2 mm for average anterior chamber depth, the sensitivity and specificity were 90.2% and 85.2% in the training set. For distinguishing PAC/PACG from PACS, a multivariate model had an AUC of 0.83, with sensitivity and specificity of 82.0% and 62.8% in the training set. The validation set confirmed the findings.

CONCLUSIONS

SS-OCT of the anterior segment showed excellent diagnostic performance distinguishing PACD from normal eyes and moderate diagnostic ability distinguishing eyes with PAC/PACG from eyes with PACS. ACD alone may provide a simple and effective way to diagnose PACD from control subjects. As ACD can be obtained using other more available modalities, this has implications for the early diagnosis of PACD.

Machine Learning-Guided Prediction of Central Anterior Chamber Depth Using Slit Lamp Images from a Portable Smartphone Device

There is currently no objective portable screening modality for narrow angles in the community. In this prospective, single-centre image validation study, we used machine learning on slit lamp images taken with a portable smartphone device (MIDAS) to predict the central anterior chamber depth (ACD) of phakic patients with undilated pupils. Patients 60 years or older with no history of laser or intraocular surgery were recruited. Slit lamp images were taken with MIDAS, followed by anterior segment optical coherence tomography (ASOCT; Casia SS-1000, Tomey, Nagoya, Japan). After manual annotation of the anatomical landmarks of the slit lamp photos, machine learning was applied after image processing and feature extraction to predict the ACD. These values were then compared with those acquired from the ASOCT. Sixty-six eyes (right = 39, 59.1%) were included for analysis. The predicted ACD values formed a strong positive correlation with the measured ACD values from ASOCT (R² = 0.91 for training data and R² = 0.73 for test data). This study suggests the possibility of estimating central ACD using slit lamp images taken from portable devices.

Smartphone-Acquired Image Photogrammetry for Detection of Shallow Anterior Chamber

Purpose

This study aimed to explore the role of smartphone imaging of the eye using two perspectives — anterior and temporal — in the detection of a shallow anterior chamber (AC). The AC depth (ACD) of an eye can be used as a surrogate marker for identification of eyes at risk of developing angle-closure disease.

Methods

A prospective observational study was conducted at a university teaching hospital in South India. Each eye was photographed with a smartphone using the two perspectives, followed by quantitative measurement of ACD using optical biometry. The percentage of nasal iris illuminated was measured from the image acquired using the flashlight method (anterior perspective), whereas pupil position relative to the cornea was measured from the image acquired using the temporal perpendicular method (temporal perspective). The receiver-operating characteristic curve and area under the curve (AUC) were studied for both perspectives independently for overall predictive accuracy in detection of shallow AC (ACD <2.7 mm, obtained by IOL Master).

Results

A total of 275 eyes were examined, of which 77 (28%) had an ACD <2.7 mm. The accuracy of detection of shallow AC was found to be 95.2% for both perspectives when used alone or in combination. AUC of the anterior perspective was 0.99 (95% CI 0.982–0.997). The AUC for the temporal perspective was 0.993 (95% CI 0.988–0.999).

Conclusion

Smartphone-acquired image photogrammetry of an eye with anterior and temporal perspectives independently and in combination provided accuracy nearing 95% in the detection of shallow AC (ACD <2.7 mm).

Registration

This trial was registered with the Clinical Trial Registry of India (CTRI/2018/09/015867, September 28, 2018).

The Global Extent of Undetected Glaucoma in Adults: A Systematic Review and Meta-analysis

TOPIC

Glaucoma is the leading cause of irreversible blindness, despite having good prognosis with early treatment. We evaluated the global extent of undetected glaucoma and the factors associated with it in this systematic review and meta-analysis.

CLINICAL RELEVANCE

Undetected glaucoma increases the risk of vision impairment, which leads to detrimental effects on the quality-of-life and socioeconomic well-being of those affected. Detailed information on the extent and factors associated with undetected glaucoma aid in the development of public health interventions.

METHODS

We conducted a systematic review and meta-analysis of population-based studies published between January 1, 1990, and June 1, 2020. Article search was conducted in online databases (PubMED, Web-of-Science), grey literatures (OpenGrey), and nongovernment organization reports. Our outcome measure was the proportion of glaucoma cases that were undetected previously. Manifest glaucoma included any form of glaucoma reported in the original studies and may include primary open-angle glaucoma (POAG), primary angle-closure-glaucoma, secondary glaucoma, or a combination thereof. Undetected glaucoma was defined as glaucoma cases that were undetected prior to diagnosis in the respective study. Random-effect meta-analysis was used to estimate the pooled proportion of undetected glaucoma. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and the Meta-analysis of Observational Studies in Epidemiology guidelines in our study.

RESULTS

We identified 61 articles from 55 population-based studies (n = 189 359 participants; n = 6949 manifest glaucoma). Globally, more than half of all glaucoma cases were undetected previously on average in each geographical region. Africa (odds ratio [OR], 12.70; 95% confidence interval [CI], 4.91-32.86) and Asia (OR, 3.41; 95% CI, 1.63-7.16) showed higher odds of undetected glaucoma as compared with Europe. Countries with low Human Development Index (HDI; <0.55) showed a higher proportion of undetected manifest glaucoma as compared with countries of medium to very high HDI (≥0.55; all P < 0.001). In 2020, 43.78 million POAG cases were projected to be undetected, of which 76.7% were in Africa and Asia.

DISCUSSION

Undetected glaucoma is highly prevalent across diverse communities worldwide and more common in Africa and Asia. Strategies to improve detection are needed to prevent excess visual disability and blindness resulting from glaucoma.

Prevalence of glaucoma in the elderly population in Taiwan: The Shihpai Eye Study

BACKGROUND

This study aimed to evaluate the prevalence, characteristics, and the awareness status of glaucoma in an elderly Chinese population.

METHODS

A total of 460 individuals aged ≥72 years were enrolled in this cross-sectional community-based eye disease screening program. Glaucoma was diagnosed according to the diagnostic criteria proposed by the International Society of Geographical and Epidemiological Ophthalmology. Characteristics of subjects with primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) were described and compared between groups using Mann-Whitney U and Fisher's exact tests.

RESULTS

Forty subjects were diagnosed with glaucoma, including 17 subjects with POAG, 22 with PACG, and one with secondary glaucoma. The estimated prevalence of glaucoma, POAG, and PACG was 8.7%, 3.7%, and 4.8%, respectively. In total, 71% of the subjects with PACG and 77% of POAG subjects presented with a normal intraocular pressure (IOP) of <19 mmHg. The demographic and ocular characteristics were similar between the two groups; however, subjects with POAG had a longer axial length and smaller vertical disc diameter than those with PACG. Further, 95% of the glaucoma subjects ever visited the eye clinic, but only 32.5% of them were aware of the disease.

CONCLUSION

Glaucoma is prevalent in the elderly population in Taiwan, but the diagnostic rate and disease awareness are low. Since most subjects with glaucoma presented with normal IOPs, optic disc evaluation is critical for diagnosing glaucoma in the elderly in Taiwan.

Peripheral anterior chamber depth and screening techniques for primary angle closure disease in community elderly Chinese

Background

To investigate the distribution of peripheral anterior chamber depth (ACD) and the relationship between peripheral ACD and gonioscopy compared to other ocular parameters for primary angle closure disease (PACD) screening. We performed a population-based survey in Pudong New District of Shanghai, China, in 2011.

Methods

Cross-sectional study. Adults 50 and older were enrolled from a population-based study using cluster random sampling in Pudong New District, Shanghai. Remote ocular screening was performed with digital anterior eye structure photography. Van Herrick measurements were used to evaluate the peripheral ACD, the depth of the peripheral anterior chamber, and corneal thickness (CT), and the ACD to CT ratio was calculated. Subjects with peripheral ACD less than 0.5 CT were made follow-up appointments for clinical examination with gonioscopy. Receiver operating characteristic curves (ROC) were generated to show the performance of different tests in screening for primary angle closure disease (PACD).

Results

Two thousand five hundred twenty-eight adults participated in the study with 91 patients diagnosed with PACD. Two thousand four hundred sixty-three subjects had valid data in the right eye available for analysis. The mean peripheral ACD values for men and women were significantly different: 1.04 ± 0.46 (range 0.11–2.93) CT and 0.87 ± 0.41 (range 0.12–2.96) CT respectively (t = − 4.18; P<0.0001). Multivariate logistic regression analysis reveals that peripheral ACD declined by 0.31 CT (P < 0.0001) per diopter of SE and was 0.19 CT (P < 0.0001) shallower in women than in men (r2 = 0.1304, P < 0.0001). Peripheral ACD performed best in screening for PACD.

Conclusions

Peripheral ACD measurement is recommended for PACD screening in community elderly Chinese.

The Genetic and Endoplasmic Reticulum-Mediated Molecular Mechanisms of Primary Open-Angle Glaucoma

Glaucoma is a heterogenous, chronic, progressive group of eye diseases, which results in irreversible loss of vision. There are several types of glaucoma, whereas the primary open-angle glaucoma (POAG) constitutes the most common type of glaucoma, accounting for three-quarters of all glaucoma cases. The pathological mechanisms leading to POAG pathogenesis are multifactorial and still poorly understood, but it is commonly known that significantly elevated intraocular pressure (IOP) plays a crucial role in POAG pathogenesis. Besides, genetic predisposition and aggregation of abrogated proteins within the endoplasmic reticulum (ER) lumen and subsequent activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK)-dependent unfolded protein response (UPR) signaling pathway may also constitute important factors for POAG pathogenesis at the molecular level. Glaucoma is commonly known as a ‘silent thief of sight’, as it remains asymptomatic until later stages, and thus its diagnosis is frequently delayed. Thereby, detailed knowledge about the glaucoma pathophysiology is necessary to develop both biochemical and genetic tests to improve its early diagnosis as well as develop a novel, ground-breaking treatment strategy, as currently used medical therapies against glaucoma are limited and may evoke numerous adverse side-effects in patients.

Modeling of gonioscopic anterior chamber angle grades based on anterior segment optical coherence tomography

Background

To quantitatively assess anterior chamber angle (ACA) structure by anterior segment optical coherence tomography (AS-OCT) and develop a model to evaluate angle width as defined by gonioscopy.

Methods

The ACAs of each quadrant were evaluated by gonioscopy, classified by the Scheie grading system, and assigned into one of the three grades: small angle (SA), moderate angle (MA), and large angle (LA). The eyes were imaged by AS-OCT, and ACA structural parameters including angle opening distance at the scleral spur (AODSS) and at 750 μm anterior to the scleral spur (AOD750), trabecular-iris space area at 750 μm anterior to the scleral spur (TISA750), and a newly defined parameter “light intersection distance” (LID), were measured. The ACA structural data were used to construct an ordered logistic regression model for assignment of ACAs to one of the three angle grades. The validity of the model was then tested.

Results

A total of 169 quadrants from 53 subjects were included in the analysis, of which 111 quadrants were included in the modeling data and 58 in the testing data. In pairwise comparisons of SA, MA, and LA by ANOVA, the measured parameters were as follows: AOD750 (0.174 ± 0.060 vs. 0.249 ± 0.068 vs. 0.376 ± 0.114 mm; P < 0.001), TISA750 (0.075 ± 0.035 vs. 0.117 ± 0.036 vs. 0.181 ± 0.062 mm²; P < 0.001), and LID (− 0.300 ± 0.187 vs. -0.085 ± 0.170 vs. 0.122 ± 0.156 mm; P < 0.001). The ACA grading model based on LID showed a relatively high correction rate of 72.4%, and the model efficiency, calculated using the receiver operating characteristic, showed an area under the curve of 0.740. Weighted kappa statistics showed a good agreement for multiple ACA grades (0.772).

Conclusions

The AS-OCT-based multiple ACA grades model was demonstrated as a non-contact approach for ACA assessment with high speed and high spatial resolution, providing guidance for diagnosis of angle closure.

Non-contact tests for identifying people at risk of primary angle closure glaucoma

BACKGROUND

Primary angle closure glaucoma (PACG) accounts for 50% of glaucoma blindness worldwide. More than three-quarters of individuals with PACG reside in Asia. In these populations, PACG often develops insidiously leading to chronically raised intraocular pressure and optic nerve damage, which is often asymptomatic. Non-contact tests to identify people at risk of angle closure are relatively quick and can be carried out by appropriately trained healthcare professionals or technicians as a triage test. If the test is positive, the person will be referred for further specialist assessment.

OBJECTIVES

To determine the diagnostic accuracy of non-contact tests (limbal anterior chamber depth (LACD) (van Herick test); oblique flashlight test; scanning peripheral anterior chamber depth analyser (SPAC), Scheimpflug photography; anterior segment optical coherence tomography (AS-OCT), for identifying people with an occludable angle.

SEARCH METHODS

We searched the following bibliographic databases 3 October 2019: CENTRAL; MEDLINE; Embase; BIOSIS; OpenGrey; ARIF and clinical trials registries. The searches were limited to remove case reports. There were no date or language restrictions in the searches.

SELECTION CRITERIA

We included prospective and retrospective cross-sectional, cohort and case-control studies conducted in any setting that evaluated the accuracy of one or more index tests for identifying people with an occludable angle compared to a gonioscopic reference standard.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed data extraction and quality assessment using QUADAS2 for each study. For each test, 2 x 2 tables were constructed and sensitivity and specificity were calculated. When four or more studies provided data at fixed thresholds for each test, we fitted a bivariate model using the METADAS macro in SAS to calculate pooled point estimates for sensitivity and specificity. For comparisons between index tests and subgroups, we performed a likelihood ratio test comparing the model with and without the covariate.

MAIN RESULTS

We included 47 studies involving 26,151 participants and analysing data from 23,440. Most studies were conducted in Asia (36, 76.6%). Twenty-seven studies assessed AS-OCT (analysing 15,580 participants), 17 studies LACD (7385 participants), nine studies Scheimpflug photography (1616 participants), six studies SPAC (5239 participants) and five studies evaluated the oblique flashlight test (998 participants). Regarding study quality, 36 of the included studies (76.6%) were judged to have a high risk of bias in at least one domain.The use of a case-control design (13 studies) or inappropriate exclusions (6 studies) raised patient selection concerns in 40.4% of studies and concerns in the index test domain in 59.6% of studies were due to lack of masking or post-hoc determination of optimal thresholds. Among studies that did not use a case-control design, 16 studies (20,599 participants) were conducted in a primary care/community setting and 18 studies (2590 participants) in secondary care settings, of which 15 investigated LACD. Summary estimates were calculated for commonly reported parameters and thresholds for each test; LACD ≤ 25% (16 studies, 7540 eyes): sensitivity 0.83 (95% confidence interval (CI) 0.74, 0.90), specificity 0.88 (95% CI 0.84, 0.92) (moderate-certainty); flashlight (grade1) (5 studies, 1188 eyes): sensitivity 0.51 (95% CI 0.25, 0.76), specificity 0.92 (95% CI 0.70, 0.98) (low-certainty); SPAC (≤ 5 and/or S or P) (4 studies, 4677 eyes): sensitivity 0.83 (95% CI 0.70, 0.91), specificity 0.78 (95% CI 0.70, 0.83) (moderate-certainty); Scheimpflug photography (central ACD) (9 studies, 1698 eyes): sensitivity 0.92 (95% CI 0.84, 0.96), specificity 0.86 (95% CI 0.76, 0.93) (moderate-certainty); AS-OCT (subjective opinion of occludability) (13 studies, 9242 eyes): sensitivity 0.85 (95% CI 0.76, 0.91); specificity 0.71 (95% CI 0.62, 0.78) (moderate-certainty). For comparisons of sensitivity and specificity between index tests we used LACD (≤ 25%) as the reference category. The flashlight test (grade 1 threshold) showed a statistically significant lower sensitivity than LACD (≤ 25%), whereas AS-OCT (subjective judgement) had a statistically significant lower specificity. There were no statistically significant differences for the other index test comparisons. A subgroup analysis was conducted for LACD (≤ 25%), comparing community (7 studies, 14.4% prevalence) vs secondary care (7 studies, 42% prevalence) settings. We found no evidence of a statistically significant difference in test performance according to setting. Performing LACD on 1000 people at risk of angle closure with a prevalence of occludable angles of 10%, LACD would miss about 17 cases out of the 100 with occludable angles and incorrectly classify 108 out of 900 without angle closure.

AUTHORS' CONCLUSIONS

The finding that LACD performed as well as index tests that use sophisticated imaging technologies, confirms the potential for this test for case-detection of occludable angles in high-risk populations. However, methodological issues across studies may have led to our estimates of test accuracy being higher than would be expected in standard clinical practice. There is still a need for high-quality studies to evaluate the performance of non-invasive tests for angle assessment in both community-based and secondary care settings.

Early versus Delayed Phacoemulsification and Intraocular Lens Implantation for Acute Primary Angle-Closure

Purpose

To compare the effects of early phacoemulsification and intraocular lens implantation (phaco/IOL), delayed phaco/IOL after initial laser peripheral iridotomy (LPI), and conventional LPI alone in patients with acute primary angle-closure (PAC).

Methods

Patients with acute PAC were included in the study, and those with secondary glaucoma, prior ocular trauma, or other ocular diseases and those who had undergone ocular surgeries previously were excluded. Patients were categorized into three groups: Group A, which underwent primary phaco/IOL after acute PAC; Group B, which underwent LPI initially after acute PAC, followed by phaco/IOL within 6 months; and Group C, which underwent LPI alone. The IOP control success at 12 months as well as changes in ocular characteristics and the number of antiglaucoma medications used after the treatment among the groups were evaluated.

Results

Eighty-one eyes were included in the study: 24 eyes in Group A, 23 eyes in Group B, and 34 eyes in Group C. The linear mixed model analysis demonstrated considerable IOP control in Groups A and B. Visual acuity, anterior chamber depth (ACD), and angle width improved significantly in Groups A and B, but not in Group C. The number of antiglaucoma medications used was significantly higher in Group C than in Groups A and B.

Conclusions

Patients who underwent phaco/IOL had better IOP control, improved vision, deeper ACD, and wider angle and required less antiglaucoma medications than those who underwent LPI alone. Performing phaco/IOL weeks to months after the initial LPI did not appear to adversely affect outcomes compared with those of early phaco/IOL.

Integration of Genetic and Biometric Risk Factors for Detection of Primary Angle Closure Glaucoma

PURPOSE

The purpose of this study was to investigate whether the addition of primary angle closure glaucoma (PACG)-associated genetic loci allows improved detection of PACG, compared to anterior segment parameters measured by imaging.

DESIGN

Case-control study.

METHODS

Genotype data of the 8 PACG single-nucleotide polymorphisms (SNPs) (rs11024102 at PLEKHA7, rs3753841 at COL11A1, rs1015213 located between PCMTD1 and ST18 on Chromosome 8q, rs3816415 at EPDR1, rs1258267 at CHAT, rs736893 at GLIS3, rs7494379 at FERMT2, and rs3739821 mapping in between DPM2 and FAM102A) were available. Customized software was used to measure anterior segment optical coherence tomography (ASOCT) parameters, namely, anterior chamber depth, width, and area (ACD, ACW, and ACA) and lens vault (LV). Statistical analysis for positive predictive values was modeled using the receiver operating characteristic curve (AUC). Statistical significance comparing predictive power of the different parameters was calculated using permutation.

RESULTS

A total of 388 PACG subjects and 751 controls with both ASOCT and genetic data were available for analysis. Anterior segment parameters including ACD, ACA, and LV had excellent predictive value (AUCs >0.94), except ACW (AUC=0.65), for identifying PACG. The inclusion of genetic risk alleles (either singly or as a composite genetic risk score for 8 genomewide association study SNPs) to ACD only provided a +0.50% improvement in reclassifying PACG cases and controls over and above the discriminatory value of ACD. This +0.50% improvement was not statistically significant (P > .05).

CONCLUSIONS

Although significant on their own, the incorporation of genetic data in the context of anterior segment imaging parameters like ACD provided only a marginal improvement of PACG detection.

LVPEI Glaucoma Epidemiology and Molecular Genetic Study: teleophthalmology screening for angle-closure disease in an underserved region

OBJECTIVES

To assess the ability of teleophthalmoscopic grading of peripheral anterior chamber depth (PACD) using the van Herick (vH) technique in detecting gonioscopically occludable angle; and to determine whether combining results from vH grading and ocular biometry can improve the accuracy to diagnose gonioscopically occludable angle METHODS: This cross-sectional study was an offshoot of a rural population-based study, Glaucoma Epidemiology and Molecular Genetic Study (GLEAMS). A masked urban ophthalmologist graded digital slit lamp photographs of PACD by vH technique. Sussman four-mirror lens was used to perform dark room indentation gonioscopy. Cutoff values of the tests were, vH technique: grade ≤ 2, central anterior chamber depth (ACD), as well as axial length: ≤ 25th percentile and lens thickness ≥ 75th percentile value of the study population.

RESULTS

We studied 1965 eyes of 1029 adult participants. The vH grade was ≤2 in 188 (9.5%) eyes. The angle was occludable by gonioscopy in 101 (5.1%) eyes. The performance of the vH test to rule out gonioscopically occludable angle was good [negative predictive value (NPV): 97.3%], despite low sensitivity (52.5%), while its efficacy to rule in the condition was low [positive predictive value (PPV): 28.2%] despite high specificity (92.8%). However, test combination strategy increased the PPV nearly twofold (53.8%). The calculated PPV at 10% prevalence of gonioscopically occludable angle was even higher (70.5%).

CONCLUSIONS

Van Herick technique can be incorporated into a teleophthalmology program by means of slit lamp photographs of PACD. Combined vH grading and ocular biometry improved the predictability of a gonioscopically occludable angle.

Combination of Simple Diagnostic Tests to Detect Primary Angle Closure Disease in a Resource-constrained Region

Purpose: To report on diagnostic accuracy of van Herick (vH) technique performed by a vision technician (VT) as well as on efficacy of a combination of vH technique and central anterior chamber depth (ACD) in detection of primary angle closure disease.Methods: Data was obtained from two cohorts; rural clinic setting (n = 111), and rural population-based research setting (n = 888). Van Herick grading was performed by a VT in first cohort and a glaucoma specialist in second cohort. A reference standard four-mirror gonioscopy was performed by a glaucoma specialist in both cohorts. We did preferential sampling. Cut-off levels for vH technique and central ACD were grade 2 and 25^th percentile value, respectively. Data from one eye per participant was analyzed.Results: Three hundred and forty (34%) eyes were gonioscopically occludable. Area under receiver operating characteristic curve (95% confidence interval) for vH test was 0.83 (0.76, 0.9) and 0.81 (0.78, 0.84) in first and second cohorts, respectively. Simultaneous testing achieved sensitivity of 87.8% while sequential testing achieved specificity of 99.3%. Negative predictive value* of simultaneous testing was 98.3% compared to 96.6% of vH technique while positive predictive value* of sequential testing was 86% compared to 49.3% of vH technique. (*at 10% prevalence of gonioscopically occludable angle)Conclusions: Diagnostic accuracy of vH grading was similar when performed by a VT and a glaucoma specialist. While test combination was effective to rule in, vH technique may suffice to rule out the disease. Implications of these findings for resource-constrained regions are discussed.

Transitions of the Understanding and Definition of Primary Glaucoma

Objective:

In previous decades, glaucoma has been primarily attributed to elevated intraocular pressure (IOP), but this has gradually been replaced by the development of optic neuropathy as the central concept of glaucoma in developed countries. However, there still remain strong controversies in the definition of glaucoma in China. In this current review, we are going to discuss these controversies and elaborate on the historical transitions of the definition of glaucoma both in China and developed countries. Furthermore, we will briefly describe the “ocular-cranial pressure gradient” theory and discuss the relationship between glaucoma and degenerative diseases of the central nervous system (CNS) in order to show the complex pathogenesis of glaucoma and the importance for the modification to the definition of glaucoma.

Data Sources:

We performed a comprehensive search in both PubMed and SinoMed using the following keywords: (a) “primary glaucoma” and “guideline,” (b) “ocular-cranial pressure gradient,” and (c) “glaucoma,” “Alzheimer's disease,” and “Parkinson's disease.” The literature search included the related articles with no restrictions on publication date.

Study Selection:

The primary references were Chinese and English articles including (a) original guidelines and expert consensuses of primary glaucoma, (b) reviews focusing on the differences between various versions of these guidelines and consensuses, and (c) papers about ocular-cranial pressure gradient theory and the relationship between glaucoma and CNS degenerative diseases.

Results:

The definitions and classifications of both primary open-angle glaucoma and primary angle-closure glaucoma differ between Chinese glaucoma consensuses and international primary glaucoma guidelines. Chinese definitions and classifications put more emphasis on the IOP, while international guidelines put more emphasis on the presence of optic neuropathy. The ocular-cranial pressure gradient theory and the research on the relationship between glaucoma and CNS degenerative diseases have provided new directions for exploring the pathogenesis of glaucoma.

Conclusions:

As regards the definition and classification of primary glaucoma, we find that there are still some discrepancies between Chinese expert consensuses and international guidelines. Glaucoma is a disease with complex etiologies, while its common characteristic is a specific optic neuropathy. The current definition and understanding of glaucoma is an ongoing and evolving process, reflecting our latest available evidence on its pathogenesis. Chinese ophthalmology community may need to update our guidelines, accommodating these latest developments.

Predicting the outcome of laser peripheral iridotomy for primary angle closure suspect eyes using anterior segment optical coherence tomography

PURPOSE

Develop an algorithm to predict the success of laser peripheral iridotomy (LPI) in primary angle closure suspect (PACS), using pretreatment anterior segment optical coherence tomography (ASOCT) scans.

METHODS

A total of 69 eyes with PACS underwent LPI and time-domain ASOCT scans (temporal and nasal cuts) were performed before and after LPI. After LPI, success is defined as one or more angles changed from closed to open. All the pretreatment ASOCT scans were analysed using the Anterior Segment Analysis Program to derive anterior chamber angle (ACA) measurements. The measurements for each angle were ordered along with angle-independent measurements totalling to 42 measurements which serve as features for the prediction algorithm. Two masked glaucoma fellowship-trained ophthalmologists graded the pre-LPI ASOCT scans to determine whether LPI was likely to successful.

RESULTS

There were 42 (60.9%) eyes that fulfilled the criteria for success after LPI. Iris concavity, angle recess area (750 μm) and iris concavity ratio showed the highest predictive score and were selected using correlation-based subset selection method. These features were classified into two ('successful' and 'unsuccessful') categories using a Bayes classifier. The algorithm predicted the success of LPI with 79.28% cross validation accuracy, which was superior to the predictive accuracy of the ophthalmologists (kappa 0.497 and 0.636 respectively).

CONCLUSION

Using pretreatment ASOCT scans, our algorithm was superior to ophthalmologists in predicting the success of LPI for PACS eyes. This novel algorithm could aid decision making in offering LPI as a prophylaxis for PACS.

Diagnostic Accuracy of Van Herick Technique to Detect Pre-Disease States of Primary Angle Closure Glaucoma in a Resource Constraint Region

OBJECTIVES

To critically evaluate diagnostic accuracy of the van Herick (vH) technique in detection of gonioscopically occludable angle in a rural population and to explore ways to improve accuracy of the technique Methods: The study cohort was formed by two-stage cluster random sampling. Peripheral anterior chamber depth grading was performed, using both traditional and modified (photographic comparison) vH techniques, under dark adapted and standard lighting conditions by a comprehensive ophthalmologist masked to the clinical features. The cut-off criterion for vH test was 25% of peripheral corneal thickness. The reference standard was dark room 4-mirror indentation gonioscopy performed by an experienced glaucoma specialist. This study adhered to the STARD guidelines for reporting diagnostic accuracy studies.

RESULTS

We studied 111 eyes of 111 participants. The median age was 62 years. The angle was occludable by gonioscopy in 69 (62%) eyes; 58 eyes were primary angle closure suspects and 11 were primary angle closure patients. The likelihood ratio (95% confidence interval (CI)) of the positive (LR+) and negative (LR‒) result by the traditional vH technique was 5.17 (2.43, 11) and 0.30 (0.20, 0.46), respectively. The LR+ by reducing and LR‒ by elevating the cut-off grade of the traditional vH technique were 9.4 (2.3, 37.4) and 0.08 (0.02, 0.31), respectively. The area under receiver operating characteristic curve did not differ significantly by photographic comparison or lighting condition (p = 0.13).

CONCLUSIONS

vH grading can be considered as a triage test before gonioscopy. The value of the vH technique to the diagnostic strategy is discussed.

Low Sensitivity of the Van Herick Method for Detecting Gonioscopic Angle Closure Independent of Observer Expertise

PURPOSE

To evaluate the diagnostic performance characteristics of the Van Herick assessment (VHA) for identifying angle closure compared to gold-standard gonioscopy, as conducted by trained observers of varying expertise.

DESIGN

Reliability analysis.

METHODS

Patients (n = 131) from a glaucoma referral clinic aged ≥50 years without prior ocular surgery or iridotomy underwent unilateral VHA by 1 of 11 trained ophthalmic technicians, followed by VHA and indirect gonioscopy by 1 of 15 ophthalmology residents and 1 of 4 glaucoma specialist attending physicians. Observers were masked to others' gradings. Cohen's kappa (κ) assessed test reproducibility. VHA sensitivity and specificity for identifying gonioscopic angle closure were calculated.

RESULTS

Mean patient age was 62.0 ± 8.7 years, 56% of patients were male, and 84% were African American. Angles were gonioscopically closed in 14.5% of eyes. Moderate agreement was observed comparing technician or resident VHA to attending VHA (κ = 0.48 and κ = 0.56, respectively). Resident and attending gonioscopy demonstrated excellent agreement (κ = 0.94). Sensitivities of technician, resident, and attending VHA for detecting angle closure were 57.9% (95% confidence interval: 34.0%-78.9%), 78.9% (53.9%-93.0%), and 68.4% (43.5%-86.4%), respectively. Specificities were 88.5% (80.3%-93.6%), 88.2% (80.3%-93.3%), and 87.5% (79.6%-92.8%), respectively.

CONCLUSIONS

VHA, even when performed by experienced ophthalmologists, misses a substantial proportion of angle closure while incorrectly identifying roughly 1 in 8 open-angle eyes as closed. These results suggest that clinical assessment of anterior chamber angle configuration is best accomplished with gonioscopy.

Risk Factors Associated with Missed Diagnoses of Narrow Angles by the Van Herick Technique

PURPOSE

To identify which factors are associated with a deep-appearing anterior chamber on slit-lamp examination by the Van Herick (VH) technique in eyes with a diagnosis of narrow angle (NA) on gonioscopy.

DESIGN

Retrospective review.

PARTICIPANTS

One thousand three hundred fourteen eyes in 696 participants with NA on indirect gonioscopy.

METHODS

All included eyes were graded as narrow with iridotrabecular contact on indirect gonioscopy in a darkened room by a single trained glaucoma specialist. Before gonioscopy, eyes were graded as narrow or deep by VH slit-lamp examination technique. Demographic and clinical factors predictive of a deep VH grading were assessed using logistic regression with generalized estimating equations.

MAIN OUTCOME MEASURES

Factors associated with deep versus narrow VH grade.

RESULTS

Using the VH technique, 13.7% of eyes (n = 180/1314) with NA on gonioscopy were classified as deep. Eyes with primary angle-closure glaucoma (PACG; odds ratio, 2.43; P < 0.001) and primary angle closure (PAC; odds ratio, 1.38; P = 0.006) were significantly more likely to be graded as deep by the VH technique relative to eyes that were primary angle-closure suspects (PACSs). In multivariate analysis, male gender (odds ratio, 2.22; P < 0.001), myopia (odds ratio, 1.4; P = 0.048), and black (odds ratio, 4.11; P < 0.001) and Asian (odds ratio, 2.24; P = 0.044) race were independent risk factors for a deep grading with the VH technique in eyes with NA on gonioscopy.

CONCLUSIONS

Patients with NAs on gonioscopy who are men, myopic, and of black or Asian race are at increased risk of being misdiagnosed with deep angles if examined with the VH technique alone. Eyes with PACG and PAC may be more likely than those with PACS to be misdiagnosed as deep with the VH technique. It is possible that by being missed by the VH technique, these eyes could have progressed from PACS to PAC and PACG. Patients with these demographic and clinical characteristics in the presence of other risk factors for glaucoma should undergo careful gonioscopy.

The Prevalence and the Incidence of Diagnosed Open-Angle Glaucoma and Diagnosed Angle-Closure Glaucoma: Changes From 2001 to 2010

PURPOSE

To explore the trends in diagnosed open-angle glaucoma (OAG) and diagnosed angle-closure glaucoma (ACG) in Taiwan during the period of 2001 to 2010.

MATERIALS AND METHODS

Data were sourced from the National Longitudinal Health Insurance Database 2000 (LHID2000). The study population comprised all patients with a diagnosis of OAG or ACG (International Classification of Diseases, 9th Revision, Clinical Modification codes 365). Patients were stratified by their sex and age; differences in standardized incidence rates were compared between the stratified groups.

RESULTS

Throughout the study period, the prevalence of diagnosed OAG (slope=0.18, P<0.0001) and ACG (slope=0.09, P<0.0001) increased. Before 2005, the prevalence of ACG was higher than that of OAG; however, from 2005 to 2010, the prevalence of OAG was higher than that of ACG. The standardized incidence of diagnosed OAG increased insignificantly (slope=1.06, P=0.18), and that of diagnosed ACG decreased significantly (slope=-1.17, P=0.009). The prevalence and the incidence of OAG and ACG were the highest among people of advanced age. Women had higher standardized incidence rates of ACG during the study period. Men had higher standardized incidence rates of OAG in every year of the study with the exception of 2007.

CONCLUSIONS

In Taiwan, ACG was more prevalent in women and OAG might be more prevalent in men. The prevalence of ACG was higher than that of OAG before 2005, but the prevalence of OAG has been higher than that of ACG since 2005.

Ethnic differences in lens parameters measured by ocular biometry in a cataract surgery population

Purpose

To investigate whether differences exist in lens position and other lens parameters among major ethnic groups with cataractous eyes, which may help explain racial differences in angle closure risk.

Methods

This retrospective, cross-sectional study included 807 adult patients who had cataract surgery between years 2014 and 2016 at the University of California, San Francisco (UCSF). Adult patients of white, Asian, Hispanic and African-American ethnicity were included. Lens position (LP), defined as anterior chamber depth (ACD) + 1/2 lens thickness (LT), was assessed using measurements from optical biometry. Other assessed biometric parameters included axial length (AL), relative lens position (RLP) (defined as LP/AL), and anterior chamber depth (ACD).

Results

A total of 807 patients and 1361 eyes were included in this study from a database of patients having cataract surgery. Mean age was 69.2 years (age range from 18 to 101 years old), and 60.3% of patients were women. The mean LP measurements were 5.54±0.32 mm for white, 5.38±0.32 mm for Asian, 5.32±0.30 mm for Hispanic, and 5.40±0.28 mm for African-American participants. After adjusting for age, sex, and AL, significant differences were found when comparing LP in paired comparisons among White cohort with Asians (P<0.001), Hispanics (P<0.001) and African-Americans (P = 0.003). Additionally, when comparing RLP, similar significant results were found when comparing Whites with Asians (P<0.001), Hispanics (P<0.001) and African-Americans (P = 0.002). Lastly, pair-wise comparison of LT between ethnic groups showed significant differences while comparing Asians with Whites (P = 0.001) and Asians with African-Americans (P<0.001).

Conclusion

The results of this study suggest that the LP of Hispanic, Asian, and African-American patients are significantly smaller than that of White patients, and among all ethnic groups, Hispanics and after Asians have the smallest LP (P<0.001) and RLP (P<0.001). These findings may have implications for the relative risk of angle closure and the potential IOP response after cataract surgery among different ethnic groups.

Ocular findings in adult subjects with an inactivating mutation in GH releasing hormone receptor gene

OBJECTIVE

Ocular function is fundamental for environmental adaptation and survival capacity. Growth factors are necessary for a mature eyeball, needed for adequate vision. However, the consequences of the deficiency of circulating growth hormone (GH) and its effector insulin-like growth factor I (IGF-I) on the physical aspects of the human eye are still debated. A model of untreated isolated GH deficiency (IGHD), with low but measurable serum GH, may clarify this issue. The aim of this study was to assess the ocular aspects of adult IGHD individuals who have never received GH therapy.

DESIGN

Cross sectional study.

METHODS

Setting: University Hospital, Federal University of Sergipe, Brazil.

PATIENTS

Twenty-five adult (13 males, mean age 50.1years, range 26 to 70years old) IGHD subjects homozygous for a null mutation (c.57+1G>A) in the GHRH receptor gene, and 28 (15 males, mean age 51.1years, range 26 to 67years old) controls were submitted to an endocrine and ophthalmological assessment. Forty-six IGHD and 50 control eyes were studied.

MAIN OUTCOME MEASURES

Visual acuity, intraocular pressure, refraction (spherical equivalent), ocular axial length (AL), anterior chamber depth (ACD), lens thickness (LT), vitreous depth (VD), mean corneal curvature (CC) and central corneal thickness (CCT).

RESULTS

IGHD subjects exhibited unmeasurable serum IGF-I levels, similar visual acuity, intraocular pressure and LT, higher values of spherical equivalent and CC, and lower measures of AL, ACD, VD and CCT in comparison to controls, but within their respective normal ranges. While mean stature in IGHD group was 78% of the control group, mean head circumference was 92% and axial AL was 96%.

CONCLUSIONS

These observations suggest mild ocular effects in adult subjects with severe IGF-I deficiency due to non-treated IGHD.

Haplotype analysis of association of the MYOC gene with primary angle-closure glaucoma in a Han Chinese population

PURPOSE

The aim of this study is to examine whether or not myocilin (MYOC) genetic variations are associated with susceptibility to primary angle-closure glaucoma (PACG) in the Han Chinese population.

METHODS

Four single-nucleotide polymorphisms (SNPs)-rs235913, rs183532, rs12076134, and rs235875-in the MYOC gene were genotyped in 212 adult patients with PACG and 255 age-, sex-, and ethnic-matched healthy controls by using a polymerase chain reaction-restriction fragment length polymorphism assay. Data were analyzed by chi-square analysis.

RESULTS

The four SNPs in the MYOC gene were in the Hardy-Weinberg equilibrium in all the subjects. The frequencies of A allele rs183532 were significantly different between the PACG patients and the controls (0.238 vs. 0.169, p=0.008; OR=1.541; 95% CI: 1.117-2.127). The frequencies of the AA genotype and A allele of rs235913 were increased in PACG patients compared with controls, but the difference was not significant (p=0.037, p=0.017, respectively). A comparison of the distributions of the genotypes and alleles of rs12076134 and rs235875 showed no statistically significant differences between the PACG patients and the controls (p>0.05). Haplotype analysis indicated that the frequency of the AATG and AATA haplotypes was significantly higher for PACG patients than for control subjects (both p<0.001). However, the frequency of CGGA and CGTG haplotypes was lower for PACG patients than for control subjects (p<0.001).

CONCLUSIONS

Our study suggests that rs183532 is associated with an increased risk of PACG in the Chinese Han population.

Trends in Glaucoma Medication Expenditures under Universal Health Coverage: A National Population-Based Longitudinal Survey in Taiwan

Medical care in Taiwan is well known for its low cost, high efficiency, high quality, excellent medical accessibility, and high equity. We investigate the trends in medication expenditures for glaucoma from 1997 to 2010. The results show that higher medical expenditures were incurred by patients who were aged ≥40 years, male patients, and patients in the highest salary population whereas lower medical expenditures were incurred by blue-collar workers. The medications with the most significant increases in expenditure were prostaglandin analogs (PGAs), α-agonists, and fixed combinations, whereas the medications with the most significant decreases in expenditure were β-blockers and cholinergic agonists. The number of trabeculectomies shows two downward break points in 1999 and 2000 when PGAs were listed and were reimbursed. These results suggest socioeconomic disparities in glaucoma care, as well as understanding of the changes in the expenditure of glaucoma medications under such universal health insurance coverage system.

Biometry and corneal astigmatism in cataract surgery candidates from Southern China

PURPOSE

To analyze biometry data and corneal astigmatism in cataract candidates from Southern China.

SETTING

Guangdong Eye Institute, Guangdong General Hospital, Guangzhou, China.

DESIGN

Cross-sectional hospital-based study.

METHODS

The axial length (AL), anterior chamber depth (ACD), horizontal corneal diameter (white to white [WTW]), and corneal power (keratometry [K], flat K, steep K) were measured using the IOLMaster system. Ocular biometric data were collected and analyzed between 2007 and 2011.

RESULTS

The study comprised 6750 eyes of 4561 consecutive cataract candidates with a mean age of 70.4 years ± 10.5 (SD). The mean AL, ACD, and WTW were 24.07 ± 2.14 mm, 3.01 ± 0.57 mm, and 11.68 ± 0.45 mm, respectively. All values were statistically significantly greater in men than in women (P < .001) and had a significant trend toward a decrease as age increased (P < .001). The mean K value was 44.13 ± 1.63 D. The median corneal astigmatism was 0.90 D (interquartile range, 0.54-1.43). Corneal astigmatism of 1.00 D or greater was found in 2963 eyes (43.9%), and 3590 eyes (53.2%) had against-the-rule (ATR) astigmatism. The axis of corneal astigmatism turned in the ATR direction with age.

CONCLUSIONS

This study provides reference data for cataract patients from Southern China. The profiles of ocular biometric data and corneal astigmatism can help improve surgical procedures and intraocular lens design for the Chinese population.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

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 μm 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 μm 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 μm 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.

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

PURPOSE

To develop a score along with an estimated probability of disease for detecting angle closure based on anterior segment optical coherence tomography (AS OCT) imaging.

DESIGN

Cross-sectional study.

METHODS

A total of 2047 subjects 50 years of age and older were recruited from a community polyclinic in Singapore. All subjects underwent standardized ocular examination including gonioscopy and imaging by AS OCT (Carl Zeiss Meditec). Customized software (Zhongshan Angle Assessment Program) was used to measure AS OCT parameters. Complete data were available for 1368 subjects. Data from the right eyes were used for analysis. A stepwise logistic regression model with Akaike information criterion was used to generate a score that then was converted to an estimated probability of the presence of gonioscopic angle closure, defined as the inability to visualize the posterior trabecular meshwork for at least 180 degrees on nonindentation gonioscopy.

RESULTS

Of the 1368 subjects, 295 (21.6%) had gonioscopic angle closure. The angle closure score was calculated from the shifted linear combination of the AS OCT parameters. The score can be converted to an estimated probability of having angle closure using the relationship: estimated probability = e(score)/(1 + e(score)), where e is the natural exponential. The score performed well in a second independent sample of 178 angle-closure subjects and 301 normal controls, with an area under the receiver operating characteristic curve of 0.94.

CONCLUSIONS

A score derived from a single AS OCT image, coupled with an estimated probability, provides an objective platform for detection of angle closure.

Evaluation of the Van Herick Technique for Screening for Occludable Angles in an African Population

The current gold standard for screening for angle closure and adopting universal approaches to prophylaxis is the assessment of the anterior chamber (AC) angle by gonioscopy, a technique that has substantial interobserver variability and relies on subjective assessment. Slit-lamp estimation of the peripheral anterior chamber depth (ACD) by the Van Herick technique is a noncontact approach for estimating angle width and various authors have commented on its sensitivity and specificity as a screening tool for identifying narrow angles as well as angle closure.This case series draws attention to the fact that as many as 28 out of 36 (77.78%) seemingly open angles on Van Herick test were found to be potentially occludable angles on gonioscopy. Therefore, it may be concluded that gonioscopy is essential even in patients with deep peripheral ACs, before an occludable angle can be ruled out. How to cite this article: Bhartiya S, Shaarawy T. Evaluation of the Van Herick Technique for Screening for Occludable Angles in an African Population. J Current Glau Prac 2013;7(2):88-90.

Hepatocyte growth factor genetic variations and primary angle-closure glaucoma in the Han Chinese population

PURPOSE

The aim of this study is to examine whether or not hepatocyte growth factor (HGF) genetic variations are associated with susceptibility to primary angle-closure glaucoma (PACG) in the Han Chinese population.

METHODS

Three single-nucleotide polymorphisms (SNPs)-rs5745718, rs17427817, and rs3735520-in the HGF gene were genotyped in 238 adult patients with PACG and 287 age-, sex-, and ethnically matched healthy controls by using a polymerase chain reaction restriction fragment length polymorphism assay. Data was analyzed by χ(2) analysis.

RESULTS

The three tested analyzed polymorphisms in the HGF gene were in Hardy-Weinberg equilibrium, in all the subjects. The frequencies of the genotype and allele of rs5745718 and rs1742817 in the HGF gene were significantly different between the PACG patients and the controls. On one hand, the frequencies of the CC genotype and C allele of rs5745718 were significantly decreased in PACG patients compared with controls (Pc = 1.40×10(-3); Pc = 3.21×10(-4), respectively); however, on the other hand, significantly decreased frequencies of the GG genotype and the G allele of rs17427817 were observed in PACG patients compared with the controls (Pc = 0.006,; Pc = 6.06×10(-4), respectively). A comparison of the distributions of the genotypes and alleles of rs3735520 showed no statistically significant differences between the PACG patients and the controls (pc>0.05). The haplotype analysis results showed that the CGC haplotype frequency was significantly decreased in the patients with PACG compared with the controls (pc<0.001). No difference was detected between the patients and the controls with regard to the other haplotypes.

CONCLUSIONS

Our study suggests that rs5745718 and rs17427817 are associated with a decreased risk of PACG in the Chinese Han population. The CGC haplotype was demonstrated to possibly play a protective role against PACG in this population.

Investigation of the human anterior segment in normal Chinese subjects using a dual Scheimpflug analyzer

PURPOSE

To investigate anterior segment parameters in normal Chinese subjects and study factors influencing these parameters, such as age, gender, and laterality.

DESIGN

A prospective observational case series.

PARTICIPANTS

A total of 291 normal subjects (582 eyes) were included.

METHODS

The anterior segment data were determined with a dual Scheimpflug analyzer.

MAIN OUTCOME MEASURES

The corneal thinnest-point thickness (CTPT), corneal thinnest-point distribution (CTPD), central corneal thickness (CCT), corneal thickness (CT) in the central 10 mm diameter, pupil diameter (PD), pupil center distribution (PCD), anterior chamber depth (ACD), and anterior chamber volume (ACV, 8-mm diameter) were measured.

RESULTS

The mean distance between the thinnest point and the corneal vertex was 0.70 ± 0.32 mm in the right eyes and 0.42 ± 0.25 mm in the left eyes; the thinnest point was located in the inferior temporal region in 71.1% of the right eyes and 55% of the left eyes. The CCT values were thicker than the CTPT values, and they were positively correlated (right eyes r = 0.994, P<0.001; left eyes r = 0.997, P<0.001). The distance between the pupillary center and the corneal vertex was approximately 0.39 ± 0.27 mm in the right eyes and 0.37 ± 0.24 mm in the left eyes. Furthermore, the percentage of pupillary centers located in the superior regions was 72.2% in the right eyes and 73.5% in the left eyes. Age was negatively correlated with the peripheral CT (7-10 mm diameter), PD, ACD, and ACV of both eyes and the mid-peripheral CT (4-7 mm diameter) of the right eye. Laterality correlated with CTPT (P<0.001) and PD (P<0.001), whereas gender correlated with ACD (P<0.001) and ACV (P = 0.009).

CONCLUSIONS

The majority of the thinnest corneal points were located in the inferior temporal quadrant, and the pupillary center was located in the superior region of the cornea; both differed substantially from the corneal vertex. The CT increased gradually from the center to the periphery. Age, gender, and laterality correlated with some indexes.

Angle closure in Caucasians--a pilot, general ophthalmology clinic-based study

PURPOSE

To assess the rate of clinically significant angle closure in a predominantly Caucasian, clinic-based population, and consequently find out whether gonioscopy should be included in the routine ophthalmic examination.

METHODS

Patients aged ≥40 years with hyperopia ≥1 D were consecutively recruited in a community general ophthalmology clinic. Detailed darkroom gonioscopy was done, and primary angle closure was diagnosed if there was iridotrabecular apposition >180 degrees not secondary to an identifiable ocular disorder. Biometric parameters were measured and compared between the eyes with and without angle closure.

RESULTS

Eighty-four eyes from 84 patients (aged 61.3±8.9 y) were enrolled. There were 52 female (62%) and 32 male. Fourteen patients (16.7%) were diagnosed with angle closure. A statistically significant difference was observed between the eyes with and without angle closure in mean axial length (22.07±0.72 vs. 22.61±0.97, P=0.028), anterior chamber depth (ACD) (2.45±0.33 vs. 2.89±0.32, P<0.001), and lens thickness (4.97±0.3 vs. 4.62±0.4, P=0.002). Degree of hyperopia was marginally significant (3.13±2.3 vs. 2.45±1.5, P=0.09). In a logistic regression model, only ACD remained statistically significantly different (P=0.016). We tested the ability of ACD to distinguish eyes with angle closure. The area under the receiver operating characteristic curve was 0.824; using a cutoff ACD value of 2.65 mm, sensitivity was 0.786 with a specificity of 0.812.

CONCLUSIONS

Clinically significant angle closure, mandating close follow-up or preventive procedures, may be more common in Caucasians than currently thought. We recommend that gonioscopy should be included in the routine ophthalmic examination of all adults with hyperopia.

Epidemiology of glaucoma: what's new?

Globally, there are an estimated 60 million people with glaucomatous optic neuropathy and an estimated 8.4 million people who are blind as the result of glaucoma. These numbers are set to increase to 80 million and 11.2 million by 2020. Glaucoma is the second leading cause of blindness globally. The highest prevalence of open-angle glaucoma occurs in Africans, and the highest prevalence of angle-closure glaucoma occurs in the Inuit. Population-based screening for open-angle glaucoma is not recommended. Screening for angle-closure may be feasible.

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

PURPOSE

To describe the distribution and determinants of lens vault and to investigate the association of lens vault with narrow angles.

DESIGN

Prospective cross-sectional study.

METHODS

Phakic subjects 50 years and older were evaluated at a primary healthcare clinic with gonioscopy, partial laser interferometry, and anterior segment optical coherence tomography (AS-OCT). Narrow angles were defined as posterior trabecular meshwork not visible for ≥2 quadrants on non-indentation gonioscopy. Lens vault was defined as the perpendicular distance between the anterior pole of the crystalline lens and the horizontal line joining the 2 scleral spurs on horizontal AS-OCT scans. Analysis of covariance, multivariate logistic regression, and area under the receiver operating characteristic curves (AUC) were performed.

RESULTS

Of the 2047 subjects recruited, 582 were excluded because of poor image quality or inability to locate scleral spurs, leaving 1465 subjects for analysis. Eyes with narrow angles had greater lens vault compared to eyes with open angles (775.6 µm vs 386.5 µm, P < .0001). Women had significantly greater lens vault than men (497.28 µm vs 438.56 µm, P < .001), and lens vault increased significantly with age (P for trend <.001). Adjusted for age and sex, significant associations with greater lens vault were shorter axial length, shallower anterior chamber depth(ACD), higher intraocular pressure, and more hyperopic spherical equivalent (all P < .001). On multivariate analysis, subjects with lens vault >667.6 µm were more likely to have narrow angles (OR 2.201, 95% CI: 1.070-4.526) compared to those with lens vault ≤462.7 µm. The AUC for lens vault (0.816) and ACD (0.822) for detecting narrow angles were similar (P = .582).

CONCLUSIONS

Lens vault was independently associated with narrow angles and may be useful in screening to detect eyes with narrow angles.