Genome-wide association analyses identify three new susceptibility loci for primary angle closure glaucoma

Genetic Associations of Primary Angle-Closure Disease: A Systematic Review and Meta-Analysis

Importance

Effects of genetic variants on primary angle-closure disease remained uncertain.

Objective

To systematically review the associations of common single-nucleotide variants (SNVs) and rare coding variants with primary angle-closure disease, its subtypes (including primary angle-closure glaucoma, primary angle-closure suspect, and primary angle-closure) and progression.

Data Sources

Eligible studies from PubMed, Embase, and Web of Science were retrieved up to April 3, 2023. SNV information was extracted from eligible reports and 2 genome-wide association studies summary statistics, UK BioBank and FinnGen.

Study Selection

Studies providing analyzable genotype or allele data in a case-control design for primary angle-closure disease association and longitudinal case-only design for primary angle-closure disease progression.

Data Extraction and Synthesis

PRISMA guidelines were used for literature screening and the Newcastle Ottawa Scale for data quality assessment. Pooled effect size with 95% CIs of SNV associations were calculated using fixed- or random-effect models according to I2 statistics.

Main Outcomes and Measures

SNVs reported in 2 or more studies were meta-analyzed to generate pooled odds ratios and P values. Common and rare coding variants from single reports were summarized.

Results

Sixty-nine citations were eligible for meta-analysis on overall primary angle-closure disease, involving 206 SNVs in 64 genes or loci. Seventeen SNVs in 15 genes or loci showed associations with primary angle-closure disease, and 15 SNVs in 13 genes or loci showed associations with primary angle-closure glaucoma. Two SNVs, ABCA1 rs2422493 and ZNRF3 rs3178915, were associated only with primary angle-closure disease. Two SNVs, PCMTD1-ST18 rs1015213 and COL11A1 rs3753841, were associated with primary angle-closure suspect, and 1 SNV, MMP9 rs3918249, was associated with primary angle-closure. This systematic review and meta-analysis newly confirmed 7 genes or loci associated with primary angle-closure glaucoma: ATOH7, CALCRL, FBN1, IL6, LOXL1, MMP19, and VAV3. Common and rare coding variants in 16 genes or loci that have been associated with primary angle-closure disease were cataloged. Stratification analysis revealed different primary angle-closure disease-associated genes in different ethnic populations. Only 1 study regarding the genetic association of primary angle-closure glaucoma progression was identified.

Conclusions and Relevance

This study revealed the genetic complexity of primary angle-closure disease, involving common SNVs and rare coding variants in more than 30 genes or loci, with ethnic and phenotypic diversities. Further replication, genotype-phenotype correlation, and pathway analyses are warranted.

Post-GWAS functional analyses of CNTNAP5 suggests its role in glaucomatous neurodegeneration

Primary angle closure glaucoma (PACG) affects more than 20 million people worldwide, with an increased prevalence in south-east Asia. In a prior haplotype-based GWAS, we identified a novel CNTNAP5 genic region, significantly associated with PACG. In the current study, we have extended our perception of CNTNAP5 involvement in glaucomatous neurodegeneration in a zebrafish model, through investigating phenotypic consequences pertinent to retinal degeneration upon knockdown of cntnap5 by translation-blocking morpholinos. While cntnap5 knockdown was successfully validated using an antibody, immunofluorescence followed by western blot analyses in cntnap5-morphant (MO) zebrafish revealed increased expression of acetylated tubulin indicative of perturbed cytoarchitecture of retinal layers. Moreover, significant loss of Nissl substance is observed in the neuro-retinal layers of cntnap5-MO zebrafish eye, indicating neurodegeneration. Additionally, in spontaneous movement behavioural analysis, cntnap5-MO zebrafish have a significantly lower average distance traversed in light phase compared to mismatch-controls, whereas no significant difference was observed in the dark phase, corroborating with vision loss in the cntnap5-MO zebrafish. This study provides the first direct functional evidence of a putative role of CNTNAP5 in visual neurodegeneration.

Iris volume change with physiologic mydriasis to identify development of angle closure: the Zhongshan Angle Closure Prevention Trial

AIMS

To assess dynamic change of iris area (Iarea) and volume (VOL) with physiologic pupil dilation for progression of primary angle closure suspects.

METHODS

Participants underwent baseline examinations including gonioscopy and anterior segment OCT (AS-OCT) as part of the Zhongshan Angle Closure Prevention Trial. The AS-OCT images were obtained both in the dark and light. Progression was defined as development of primary angle closure or an acute angle closure attack. Static ocular biometrics and dynamic changes were compared between progressors and non-progressors and multivariable logistic regression was developed to assess risk factors for progression.

RESULTS

A mean 16.8% decrease in Iarea and a mean 6.26% decrease in VOL occurred with pupil dilation, while 22.96% non-progressors and 40% progressors presented VOL increases with pupil dilation. Iarea in light and dark and VOL in light were significantly smaller in progressors. In a multivariable logistic model, older age (p=0.008), narrower horizontal angle opening distance (AOD) 250 µm from the scleral spur (AOD250, p=0.001), flatter iris curvature (IC, p=0.006) and lower loss of iris volume (ΔVOL, p=0.04) were significantly associated with progression. With receiver operating characteristic analysis, the area under the curve for ΔVOL alone was 0.621, while that for the combined index (age, AOD250, IC and ΔVOL) was 0.824. Eyes with elevated intraocular pressure had less VOL loss compared with progressors developing peripheral anterior synechiae alone (p=0.055 for ΔVOL adjusted for pupil enlargement).

CONCLUSION

A smaller change in ΔVOL is an additive risk factor to identify eyes more likely to develop angle closure disease.

TRIAL REGISTRATION NUMBER

ISRCTN45213099.

Novel ancestry-specific primary open-angle glaucoma loci and shared biology with vascular mechanisms and cell proliferation

Primary open-angle glaucoma (POAG), a leading cause of irreversible blindness globally, shows disparity in prevalence and manifestations across ancestries. We perform meta-analysis across 15 biobanks (of the Global Biobank Meta-analysis Initiative) (n = 1,487,441: cases = 26,848) and merge with previous multi-ancestry studies, with the combined dataset representing the largest and most diverse POAG study to date (n = 1,478,037: cases = 46,325) and identify 17 novel significant loci, 5 of which were ancestry specific. Gene-enrichment and transcriptome-wide association analyses implicate vascular and cancer genes, a fifth of which are primary ciliary related. We perform an extensive statistical analysis of SIX6 and CDKN2B-AS1 loci in human GTEx data and across large electronic health records showing interaction between SIX6 gene and causal variants in the chr9p21.3 locus, with expression effect on CDKN2A/B. Our results suggest that some POAG risk variants may be ancestry specific, sex specific, or both, and support the contribution of genes involved in programmed cell death in POAG pathogenesis.

Beyond the optic nerve: Genetics, diagnosis, and promising therapies for glaucoma

Glaucoma stands as a leading global cause of blindness, affecting millions. It entails optic nerve damage and vision loss, categorized into open-angle and closed-angle glaucoma with subtypes like POAG, ACG, XFG, PCG, PDG, and developmental glaucoma. The pathophysiological and genetic factors behind glaucoma remain partially understood, with past studies linking intraocular pressure (IOP) levels to retinal ganglion cell death. Open-angle glaucoma involves elevated resistance to aqueous outflow via the trabecular meshwork, while angle-closure glaucoma typically sees drainage pathways obstructed by the iris. Genes have been identified for POAG, ACG, XFG, PCG, PDG, and developmental glaucoma, allowing for early-onset detection and the emergence of gene therapy as an effective treatment. Nevertheless, diagnostic and treatment options have their constraints, necessitating large-scale, well-designed studies to deepen our grasp of genetics' role in glaucoma's pathogenesis. This review delves into glaucoma's risk factors, pathophysiology, genetics, diagnosis, and available treatment options, including gene therapy. Additionally, it suggests alternative therapies like yoga and meditation as adjunct treatments for glaucoma prevention. Overall, this review advances our comprehension of the pathophysiology and genetic associations of glaucoma while highlighting the potential of gene therapy as a treatment avenue. Further research is imperative to fully elucidate the genetic mechanisms underpinning glaucoma and to devise effective treatments.

Rodent genetically modified models of glaucoma

Glaucoma, one of the leading causes of irreversible blindness worldwide, is a complex and heterogenous disease. While environmental factors are important, it is well-recognized that the disease has a strong heritable component. With the advent of large-cohort genome wide association studies, a myriad of genetic risk loci has been linked to different forms of glaucoma. Animal models have been an indispensable tool in characterizing these loci, especially if they lie within coding regions in the genome. Not only do these models connect genotype to phenotype, advancing our understanding of glaucoma pathogenesis in the process, they also have valuable utility as a platform for the pre-clinical testing of potential therapies. In this review, we will outline genetic models used for studying the major forms of glaucoma, including primary open angle glaucoma, normal tension glaucoma, primary angle closure glaucoma, pigmentary glaucoma, pseudoexfoliation glaucoma, and early onset glaucoma, including congenital and developmental glaucoma, and how studying these models have helped shed light on human glaucoma.

Genetic and Environmental Contributions of Primary Angle-Closure Glaucoma and Primary Open-Angle Glaucoma: A Nationwide Study in Taiwan

PURPOSE

To estimate the familial risks of primary angle-closure glaucoma (PACG) and primary open-angle glaucoma (POAG) and assess the relative contributions of environmental and genetic factors to these risks.

DESIGN

Retrospective, population-based cohort study.

METHODS

We used the 2000-2017 Taiwan National Health Insurance Program database to construct 4,144,508 families for the 2017 population (N = 23,373,209). We used the polygenic liability model to estimate glaucoma's heritability and familial transmission. The degree of familial aggregation of glaucoma was obtained from the adjusted relative risk for individuals whose first-degree relatives had glaucoma using Cox's model.

RESULTS

PACG and POAG prevalence rates for individuals whose first-degree relatives had PACG or POAG were 0.95% and 2.40%, higher than those of the general population (0.61% and 0.40%, respectively). The relative risk of PACG in individuals whose first-degree relatives had PACG was 2.44 (95% CI = 2.31-2.58). The relative risk of POAG in individuals whose first-degree relatives had POAG was 6.66 (95% CI = 6.38-6.94). The estimated contributions to PACG and POAG phenotypic variances were 19.4% and 59.6% for additive genetic variance, 19.1% and 23.2% for common environmental factors shared by family members, and 61.5% and 17.2% for nonshared environmental factors, respectively.

CONCLUSIONS

These data highlight the relative importance of genetic contribution to POAG and environmental contribution to PACG. Therefore, future work may need to focus on finding more novel environmental determinants of PACG.

Contemporary Approach to Narrow Angles

Glaucoma is the leading cause of irreversible blindness worldwide. Among all glaucoma types, primary angle closure glaucoma (PACG) affects approximately 23 million people worldwide, and is responsible for 50% of glaucoma-related blindness, highlighting the devastating consequences of this disease. The main mechanism of PACG is relative pupillary block. High-risk populations are female gender, Asian ethnicity, high hyperopia, short axial length, and a thick/anteriorly positioned lens. This review discusses the clinical diagnosis, classification, and management of patients with a narrow angle with and without intraocular pressure (IOP) elevation and glaucomatous optic nerve damage, including laser peripheral iridotomy (LPI), endocycloplasty (ECPL), lens extraction, and goniosynechialysis.

Glaucoma: now and beyond

The glaucomas are a group of conditions leading to irreversible sight loss and characterised by progressive loss of retinal ganglion cells. Although not always elevated, intraocular pressure is the only modifiable risk factor demonstrated by large clinical trials. It remains the leading cause of irreversible blindness, but timely treatment to lower intraocular pressure is effective at slowing the rate of vision loss from glaucoma. Methods for lowering intraocular pressure include laser treatments, topical medications, and surgery. Although modern surgical innovations aim to be less invasive, many have been introduced with little supporting evidence from randomised controlled trials. Many cases remain undiagnosed until the advanced stages of disease due to the limitations of screening and poor access to opportunistic case finding. Future research aims to generate evidence for intraocular pressure-independent neuroprotective treatments, personalised treatment through genetic risk profiling, and exploration of potential advanced cellular and gene therapies.

Association of body mass index and PXDNL gene variants with acute primary angle closure in southern Chinese population

This study aimed to evaluate the association of body mass index (BMI) and the weight-related gene, peroxidasin-like (PXDNL), with acute primary angle closure (APAC) and primary angle-closure glaucoma (PACG) in southern Chinese population. Total 4700 study subjects (1024 APAC, 781 PACG, and 2895 control subjects) with complete ophthalmic examinations were enrolled into this study. The association of BMI with APAC, PACG and ocular biometric parameters was evaluated. Three PXDNL missense variants were genotyped by TaqMan assay, and their association with APAC and PACG was also investigated. Multivariable logistic regression analysis showed that BMI and body weight were significantly associated with both APAC and PACG (P < 0.01). Multiple linear regression analysis demonstrated that each 1 kg/m2 increased in BMI was associated with 0.038 mm increase in axial length, 0.018 mm increase in central anterior chamber depth, 0.002 mm increase in lens position, 0.012 mm increase in corneal diameter and 0.014 mm decrease in lens thickness among the APAC subjects (P < 0.001), but not with PACG. Genetic association analysis identified that PXDNL rs11985241-rs16916207 CT haplotype conferred a higher risk to APAC (OR = 1.25, P = 0.004) than the TG haplotype, but not with PACG. The APAC subjects carrying the rs11985241 C or rs16916207 T alleles showed significantly lower weight than those carrying the corresponding protective alleles. In summary, this study revealed that lower BMI could be associated with higher risk of APAC. PXDNL could be a new associated gene for APAC.

The Structural Layers of the Porcine Iris Exhibit Inherently Different Biomechanical Properties

Purpose

The purpose of this study was to isolate the structural components of the ex vivo porcine iris tissue and to determine their biomechanical properties.

Methods

The porcine stroma and dilator tissues were separated, and their dimensions were assessed using optical coherence tomography (OCT). The stroma underwent flow test (n = 32) to evaluate for permeability using Darcy's Law (ΔP = 2000 Pa, A = 0.0391 mm2), and both tissues underwent stress relaxation experiments (ε = 0.5 with initial ramp of δε = 0.1) to evaluate for their viscoelastic behaviours (n = 28). Viscoelasticity was characterized by the parameters β (half width of the Gaussian distribution), τm (mean relaxation time constant), E0 (instantaneous modulus), and E∞ (equilibrium modulus).

Results

For the stroma, the hydraulic permeability was 9.49 ± 3.05 × 10-6 mm2/Pa · s, and the viscoelastic parameters were β = 2.50 ± 1.40, and τm = 7.43 ± 4.96 s, with the 2 moduli calculated to be E0 = 14.14 ± 6.44 kPa and E∞ = 6.08 ± 2.74 kPa. For the dilator tissue, the viscoelastic parameters were β = 2.06 ± 1.33 and τm = 1.28 ± 1.27 seconds, with the 2 moduli calculated to be E0 = 9.16 ± 3.03 kPa and E∞ = 5.54 ± 1.98 kPa.

Conclusions

We have established a new protocol to evaluate the biomechanical properties of the structural layers of the iris. Overall, the stroma was permeable and exhibited smaller moduli than those of the dilator muscle. An improved characterization of iris biomechanics may form the basis to further our understanding of angle closure glaucoma.

Anterior Segment Biometry in Primary Angle Closure Glaucoma Patients with Visual Field Progression: Comparison between Malays and Chinese

Objective

To compare anterior segment biometry parameters in progress and non-progress primary angle closure glaucoma (PACG) among Malay and Chinese patients.

Materials and methods

A cross-sectional study was conducted between November 2015 and December 2016 involving 75 patients with PACG (43 Malays and 32 Chinese) who were recruited from a single glaucoma center in Malaysia. Ocular examination included anterior segment biometry measurements on the selected eye. Axial length (AL) and anterior chamber depth (ACD) measurement was done using a noncontact partial coherence interferometer (IOL Master, Carl Zeiss, Germany). Anterior chamber angle (ACA) was measured by Anterior Segment-OCT (Spectralis Heidelberg, Germany). Humphrey visual field (HVF) 24-2 analysis of the same eye was conducted and compared with the HVF when diagnosis was made. Progression of PACG patients was assessed according to the Hodapp, Parrish and Anderson's (HPA) classification, they were then divided into progress and non-progress groups. Comparison of anterior segment biometry parameters between Malay and Chinese PACG patients with and without progression was analyzed using independent T test. Multivariate ANOVA analysis was used to compare the anterior segment parameters between progress and non-progress PACG patients, with adjustment for age, gender, lens status, family history and presence of diabetes mellitus.

Results

Chinese PACG patients have significant shorter AL (22.18 mm ± 0.76) and narrower ACA (11.96° ± 6.00) compared to Malay PACG patients. Among the progress group, Chinese PACG patients have significant shorter AL, shallower ACD and narrower ACA compared to Malays. However, after controlling for confounding factors, there was significant difference in ACA between Malay and Chinese PACG. There was also no significant difference of ocular biometry measurement between Chinese and Malay patients in progress and non-progress group.

Conclusion

There was racial influence in ocular biometry measurement in PACG patients. Chinese have significant narrower ACA compared to Malays. Serial AS-OCT monitoring is important in management of PACG.

How to cite this article

Neoh FP, Azhany Y, Siti-Azrin AH, et al. Anterior Segment Biometry in Primary Angle Closure Glaucoma Patients with Visual Field Progression: Comparison between Malays and Chinese. J Curr Glaucoma Pract 2023;17(1):3-8.

Corvis Biomechanical Factor Facilitates the Detection of Primary Angle Closure Glaucoma

Purpose

To characterize the corneal biomechanical properties of primary angle closure glaucoma (PACG) and to investigate the diagnostic performance of combining corneal biomechanical parameters and anterior segment parameters in detecting PACG.

Methods

This retrospective cross-sectional study evaluated 79 and 81 eyes of normal controls and patients with PACG, respectively. Corvis Biomechanical Factor (CBiF) and anterior chamber volume (ACV) were measured using the Corvis ST and Pentacam, respectively. We performed multivariable logistic regression, adjusted for age, sex, central corneal thickness, intraocular pressure, and ACV to evaluate the effect of CBiF on PACG. The area under the receiver operating curve (AUC) was calculated to compare the diagnostic performance of ACV, CBiF, and ACV-CBiF combination for detecting PACG.

Results

The median CBiF of the control and PACG groups was 6.61 (interquartile range [IQR], 6.39–6.88) and 6.20 (IQR, 5.93–6.48), respectively (P < 0.001). A lower CBiF, suggestive of decreased corneal biomechanical stability, increased the odds of PACG (odds ratio, 0.029; 95% confidence interval [CI], 0.003–0.266; P = 0.002) in the multivariable logistic regression model. The ACV–CBiF combination yielded the highest AUC (0.934; 95% CI, 0.882–0.968) compared with ACV alone (0.878; 95% CI, 0.823–0.928). The ACV-CBiF combination had significantly higher discriminatory ability than that of ACV alone (DeLong test, P = 0.004).

Conclusions

Lower CBiF and ACV may act as independent predictors for PACG. Combining ACV and CBiF may enhance detection of PACG.

Translational Relevance

The combination of corneal biomechanical parameters and anterior segment parameters enhances the detection of PACG.

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.

Impact of rs11024102 PLEKHA7, rs3753841 COL11A1 single nucleotide polymorphisms, and serum levels of oxidative stress markers on the risk of primary angle-closure glaucoma in Egyptians

Background

Primary angle-closure glaucoma (PACG) is one of the major causes of blindness in the Middle East with genetic loci and systemic oxidative stress as potential risk factors. The current case-control study aimed to investigate the associations of rs11024102 in Pleckstrin homology domain-containing family A member 7 (PLEKHA7), rs3753841 in collagen 11 A1 (COL11A1), and the systemic oxidative stress markers with PACG in Egyptian patients. Thirty-five control subjects and 64 PACG patients were enrolled in this study. The polymorphisms in PLEKHA7 and COL11A1 were analyzed using quantitative PCR, and their associations were statistically tested with PACG at homozygous, heterozygous, dominant, and recessive genetic models. The levels of malondialdehyde (MDA), advanced glycation-end product (AOPP), protein carbonyl (PC), and ischemia modified albumin (IMA) were quantitated colorimetrically, and their associations with PACG were analyzed statistically. The associations of MDA, AOPP, PC, and IMA with elevated intraocular pressure (IOP) were statistically tested.

Results

Neither significant difference in the genotype distribution nor allele frequency of PLEKHA7 11024102 T>C (p = 0.425 and 0.517, respectively) and COL11A1 rs3753841 G>A (p = 0.600 and 0.473, respectively) were recorded under any of the tested genetic models. Either rs11024102 PLEKHA7 or rs3753841 COL11A1 was not significantly (p > 0.025 after Bonferroni correction) associated with an increased risk of PACG in Egyptians. Egyptian patients with PACG showed significant elevations in the serum levels of MDA, AOPP, and PC either in patients with or without cases with diabetes mellites, hypertension, coronary vascular diseases, and smoking. Serum levels of MDA, AOPP, and PC were significantly associated with PACG in Egyptians (p < 0.013 after Bonferroni correction). However, MDA and PC only showed significant associations with the elevation in the IOP (p = 0.007 and 0.045, respectively) in PACG patients.

Conclusion

Both rs11024102 and rs3753841 could not be considered as potential gene-dependent risk factors for PACG pathogenesis in Egyptians. On the other hand, serum levels of MDA, AOPP, and PC might be considered risk factors for PACG. Moreover, MDA and PC could serve as good predictors for the elevation of the IOP in PACG disease.

Association of EFEMP1 with juvenile-onset open angle glaucoma in a patient with concomitant COL11A1-related Stickler syndrome

BACKGROUND

Juvenile onset open-angle glaucoma is described as a primary open-angle glaucoma, with an age of onset before 40 years. These patients have a higher prevalence of myopia.

PURPOSE

We describe the phenotype of juvenile onset open-angle glaucoma in a patient with a rare variant in EFEMP1 gene, who was also detected to have Stickler syndrome(STL).

METHODS

Whole exome sequencing (WES) was undertaken in 40 unrelated families where the proband had juvenile onset open-angle glaucoma (JOAG).

RESULTS

Out of these, eight were autosomal dominant, while the rest did not have any other affected first-degree relative. Out of the 8 autosomal dominant JOAG families, MYOC mutations were detected in 3(37.5%) and LTBP2 in 1(12.5%). One family (12.5%) had a rare EFEMP1 sequence variant in both affected father and daughter. The daughter also had high myopia and a pathogenic COL11A1 sequence variant that led to a coincidental diagnosis of STL in her.

CONCLUSIONS

This is a rare association of EFEMP1 and COL11A1 sequence variants in a JOAG patient with STL. The study also reiterates the association of JOAG with EFEMP1, which should be looked for, especially in families with autosomal dominant JOAG.

Acute angle-closure glaucoma concurrent with COVID 19 infection; case report

INTRODUCTION

To report three cases that developed acute angle-closure glaucoma on the background of hyponatremia due to COVID 19 infection.

METHODS

Data of patients with positive PCR result for COVID 19 infection and concurrent findings of acute angle-closure glaucoma were analysed retrospectively.

RESULTS

The common characteristic of all cases was positive PCR test for COVID 19 infection taken from the nasopharyngeal swab 4 or 5 days ago. Their serum sodium levels were lower than 135 mmol / L. At the initial ophthalmic examination, all cases had diffuse corneal edema with shallow anterior chambers and mid-dilated non-reacting pupils.The choroid was evaluated as normal by ocular ultrasonography. Intraocular pressures (IOP) of the first, second, and third cases were 35 mmHg, 44 mmHg, and 40 mm Hg, respectively. 5-10 cc/kg mannitol was given to all patients intravenously within 30 min. Simultaneously, they began to use oral acetazolamide, topical pilocarpine, beta-blocker, and prednisolone acetate drops.After stabilization of IOP, Neodymium-doped yttrium aluminum garnet;(ND: YAG) Laser iridotomy was performed on all patients. No additional fluid therapy was given to the patients other than mannitol, and it was determined that the blood sodium level remained at normal levels after diuresis.

DISCUSSION

Hyponatremia is the most common electrolyte disorder in COVID 19 infection. Hyponatremia may cause an angle-closure attack in patients with shallow anterior chamber angles.Therefore, one should be aware of the possibility of angle-closure glaucoma in patients who develop hyponatremia due to COVID 19 disease. Suspected patients should be referred to the ophthalmology department.

Interaction of background genetic risk, psychotropic medications, and primary angle closure glaucoma in the UK Biobank

BACKGROUND/AIMS

Psychotropic medications have been reported as a risk factor for angle closure disease. However, the interaction between background genetic risk for primary angle closure glaucoma (PACG) and susceptibility to angle closure disease among psychotropic medication users has not been investigated. Here we demonstrate the utility of a genome-wide polygenic risk score (PRS) in identifying and risk-stratifying subjects with PACG and investigate the association between PACG genetic burden and exposure to psychotropic medications on prevalent angle closure.

METHODS

This analysis used the UK Biobank dataset, a prospective cohort study of 502,506 UK residents. We constructed a PACG PRS for participants using genome-wide association study summary statistics from a multiethnic meta-analysis using the Lassosum method.

RESULTS

Among the 441,054 participants, 959 (0.22%) were identified as PACG cases. Individuals with PACG had higher PRS compared to those without PACG (0.24±1.03 SD vs. 0.00±1.00 SD, p<0.001) and PACG prevalence increased with each decile of higher PRS. Among individuals using psychotropic medication, those with PACG had higher average PRS (0.31±1.00 SD vs. 0.00±1.00 SD, p<0.001) and were more likely to have a PRS in upper deciles of polygenic risk (p = 0.04). At each decile of PRS, psychotropic medication use was associated with increased risk of PACG. These effects were more pronounced and significant in higher deciles.

CONCLUSION

We demonstrate the utility of a PRS for identifying individuals at higher risk of PACG. Additionally, we demonstrate an important relationship where the association between psychotropic medications use and PACG diagnosis varies across the polygenic risk spectrum.

A recurrent variant in LIM2 causes an isolated congenital sutural/lamellar cataract in a Japanese family

Background

Genetically determined cataract is both clinically and molecularly highly heterogeneous. Here, we have identified a heterozygous variant in the lens integral membrane protein LIM2, the second most abundant protein in the lens, responsible for congenital sutural/lamellar cataract in a three-generation Japanese family.

Methods

Whole exome sequencing (WES) was undertaken in one affected and one unaffected individual from a family with autosomal dominant congenital cataract to establish the underlying genetic basis.

Results

A recurrent missense variant LIM2: c.388C>T; p.R130C was identified and found to co-segregate with disease. In addition, one variant COL11A1:c.3788C>T of unknown significance (VUS) was also identified.

Conclusions

We report a variant in LIM2 causing an isolated autosomal-dominant congenital sutural/lamellar cataract in a Japanese family. This is the first report of a LIM2 variant in the Japanese population. Hence, we expand the mutation spectrum of LIM2 variants in different ethnic groups.

The genetic basis for adult onset glaucoma: Recent advances and future directions

Glaucoma, a diverse group of eye disorders that results in the degeneration of retinal ganglion cells, is the world's leading cause of irreversible blindness. Apart from age and ancestry, the major risk factor for glaucoma is increased intraocular pressure (IOP). In primary open-angle glaucoma (POAG), the anterior chamber angle is open but there is resistance to aqueous outflow. In primary angle-closure glaucoma (PACG), crowding of the anterior chamber angle due to anatomical alterations impede aqueous drainage through the angle. In exfoliation syndrome and exfoliation glaucoma, deposition of white flaky material throughout the anterior chamber directly interfere with aqueous outflow. Observational studies have established that there is a strong hereditable component for glaucoma onset and progression. Indeed, a succession of genome wide association studies (GWAS) that were centered upon single nucleotide polymorphisms (SNP) have yielded more than a hundred genetic markers associated with glaucoma risk. However, a shortcoming of GWAS studies is the difficulty in identifying the actual effector genes responsible for disease pathogenesis. Building on the foundation laid by GWAS studies, research groups have recently begun to perform whole exome-sequencing to evaluate the contribution of protein-changing, coding sequence genetic variants to glaucoma risk. The adoption of this technology in both large population-based studies as well as family studies are revealing the presence of novel, protein-changing genetic variants that could enrich our understanding of the pathogenesis of glaucoma. This review will cover recent advances in the genetics of primary open-angle glaucoma, primary angle-closure glaucoma and exfoliation glaucoma, which collectively make up the vast majority of all glaucoma cases in the world today. We will discuss how recent advances in research methodology have uncovered new risk genes, and how follow up biological investigations could be undertaken in order to define how the risk encoded by a genetic sequence variant comes into play in patients. We will also hypothesise how data arising from characterising these genetic variants could be utilized to predict glaucoma risk and the manner in which new therapeutic strategies might be informed.

The genetics of glaucoma: Disease associations, personalised risk assessment and therapeutic opportunities-A review

Glaucoma refers to a heterogenous group of disorders characterised by progressive loss of retinal ganglion cells and associated visual field loss. Both early-onset and adult-onset forms of the disease have a strong genetic component. Here, we summarise the known genetic associations for various forms of glaucoma and the possible functional roles for these genes in disease pathogenesis. We also discuss efforts to translate genetic knowledge into clinical practice, including gene-based tests for disease diagnosis and risk-stratification as well as gene-based therapies.

Pathogenesis of glaucoma: Extracellular matrix dysfunction in the trabecular meshwork-A review

The trabecular meshwork regulates aqueous humour outflow from the anterior chamber of the eye. It does this by establishing a tunable outflow resistance, defined by the interplay between cells and their extracellular matrix (ECM) milieu, and the molecular interactions between ECM proteins. During normal tissue homeostasis, the ECM is remodelled and trabecular cell behaviour is modified, permitting increased aqueous fluid outflow to maintain intraocular pressure (IOP) within a relatively narrow physiological pressure. Dysfunction in the normal homeostatic process leads to increased outflow resistance and elevated IOP, which is a primary risk factor for glaucoma. This review delineates some of the changes in the ECM that lead to gross as well as some more subtle changes in the structure and function of the ECM, and their impact on trabecular cell behaviour. These changes are discussed in the context of outflow resistance and glaucoma.

Evaluation of MYRF as a candidate gene for primary angle closure glaucoma

PURPOSE

Primary angle-closure glaucoma (PACG) is a leading cause of blindness. Despite tremendous human effort and financial input, no definitive causative gene has been identified either through genome-wide association or Mendelian family studies. In the current study, novel candidate genes for PACG were investigated by studying the variants of nanophthalmos-associated genes.

METHODS

A case-control study was conducted that included 45 PACG patients and 12 normal controls with short axial length (AL, less than 23.5 mm but more than 20.5 mm). Whole-exome sequencing (WES) was performed to screen the variants in previously identified nanophthalmos-associated genes, as well as other risk genes.

RESULTS

The age range of the 45 PACG patients was 24 to 80 years, with an average AL of 21.87±0.65 mm (range: 20.54-23.45 mm) in the right eye and 21.89±0.64 mm (range 20.60-23.23 mm) in the left eye. Four novel myelin regulatory factor (MYRF) gene missense variants (p.G117S, p.H1057R, p.H230R, and p.R316C) were identified in four out of the 45 enrolled PACG patients, respectively. No MYRF or other nanophthalmos-associated gene variants were detected in the 12 normal controls.

CONCLUSIONS

An appropriate approach was adopted to investigate the genetics of PACG through nanophthalmos-associated genes. A genetic variant, MYRF, was identified in four out of 45 PACG patients, which might be a novel candidate gene for PACG.

Genetic Markers PLEKHA7, ABCC5, and KALRN Are Not Associated With the Progression of Primary Angle Closure Glaucoma (PACG) in Malays

Introduction PLEKHA7, ABCC5, and KALRN have been identified as susceptible genetic markers related to glaucoma. We aimed to investigate the association between the identified susceptible genetic markers PLEKHA7 rs11024102, ABCC5 rs17217796, and KALRN rs1392912 in the progression of primary angle-closure glaucoma (PACG) in Malay patients. Methods For this study, 163 Malay patients with PACG were recruited from April 2015 to April 2017 at Hospital Universiti Sains Malaysia and Hospital Raja Perempuan Zainab II, Kota Bharu. Venesection was performed. DNA was extracted using a commercial DNA extraction kit. The primer was optimized for rs11024102, rs17217796, and rs1392912 of the PLEKHA7, ABCC5, and KALRN genes, respectively. Polymerase chain reaction (PCR) was performed, and PCR products were purified. A DNA sequencer was used to identify polymorphisms. Progression was based on the agreement between the Advanced Glaucoma Intervention Study scoring system and the Hodapp-Parrish and Anderson staging system. The scoring was conducted on two reliable consecutive Humphrey visual fields (HVFs) during the recruitment period and two baseline HVFs obtained when the diagnosis was made. Based on the scoring, patients were grouped into progressed and non-progressed. A chi-square test was used to analyze the association between the genetic markers and the progression of PACG. Results One hundred and sixty-three Malay patients with PACG (58 men and 105 women) were recruited. Twenty-nine patients (18%) had visual field progression of PACG after a mean (SD) follow-up of 6.0 (1.0) years. The minor allele frequencies for PLEKHA7 rs11024102 (G/A), ABCC5 rs17217796 (C/G), and KALRN rs1392912 (A/G) were 0.44, 0.08, and 0.48, respectively. We found that rs11024102 (p=0.828), rs17217796 (p=0.865), and rs1392912 (p=0.684) were not associated with PACG progression in the Malay patients. Conclusion Although PLEKHA7 and ABCC5 were found to be genetic markers associated with the risk of PACG, they played no roles in PACG progression in the Malay population. Moreover, KALRN was not significantly associated with PACG progression. Other susceptible genetic markers may be responsible for PACG progression.

Epidemiological Characteristics of Inpatients Undergoing Surgery for Glaucoma at Tianjin Eye Hospital from 2013 to 2017

Purpose

To analyze the epidemiological characteristics of inpatients who underwent surgery for glaucoma at Tianjin Eye Hospital from 2013 to 2017.

Methods

All glaucoma inpatients who underwent surgery at Tianjin Eye Hospital from 2013 to 2017 were evaluated. The relationships of age and sex with different types of glaucoma were analyzed. The differences in the prevalence and family history of glaucoma among patients with different systemic diseases were compared. Additionally, the effects of different surgical methods for primary angle-closure glaucoma (PACG) and primary open-angle glaucoma (POAG) were compared.

Results

A total of 4539 patients with glaucoma were retrospectively analyzed. The most prevalent type was PACG (60.15%), followed by secondary glaucoma (SG, 25.53%), POAG (7.6%), uncontrollable intraocular pressure (IOP) after antiglaucoma surgery (4.71%), mixed glaucoma (MG, 10%), and congenital glaucoma (CG, 0.9%). The main surgical methods were phacoemulsification (phaco), phacotrabeculectomy (phaco-trab), and trabeculectomy (trab). The rate of phaco-trab increased, while that of trab decreased. The proportion of women in the PACG group was higher than those in the POAG and SG groups, and there was a pronounced tendency for family clustering (P < 0.001), while in the POAG and SG groups, the proportions of men and those with diabetes were higher (P < 0.05).

Conclusions

In Tianjin Eye Hospital from 2013 to 2017, the main type of glaucoma was PACG. Female sex and a family history of glaucoma were risk factors for PACG, while male sex and hyperglycemia were risk factors for POAG and SG. Among the antiglaucoma surgery methods, the proportion of phaco-trab increased, while the proportion of trab decreased.

The Heritability of Primary Angle Closure Anatomic Traits and Predictors of Angle Closure in South Indian Siblings

PURPOSE

To estimate the heritability of ocular biometric and anterior chamber morphologic parameters and to determine predictors of angle closure concordance in South Indian probands with angle closure and their siblings DESIGN: Prospective observational cohort study METHODS: Subjects received a standardized ophthalmic examination, A-scan ultrasonography, pachymetry, and anterior segment optical coherence tomography (ASOCT) imaging. Heritability was calculated using residual correlation coefficients adjusted for age, sex, and home setting. Concordant sibling pairs were defined as both proband and sibling with angle closure. Predictors of angle closure concordance among siblings were calculated using multivariable logistic regression models.

RESULTS

A total of 345 sibling pairs participated. All anterior chamber parameters were highly heritable (P < .001 for all). Similarly, all iris parameters, axial length, lens thickness (LT), central corneal thickness, anterior lens curvature, lens vault (LV), spherical equivalent, and intraocular pressure were moderately to highly heritable (P < .004 for all). LV and LT were more heritable among concordant siblings (P < .05 for both). In contrast, ASOCT angle parameters had statistically insignificant heritability estimates. In multivariable analyses, siblings older than their probands were more likely to be concordant for angle closure (OR 1.05, 95% CI 1.01, 1.09; P = .02) and siblings with deeper anterior chamber depths (ACDs) compared to their proband were less likely to be concordant for angle closure (OR 0.74, 95% CI 0.64, 0.86; P < .001).

CONCLUSIONS

Iris, anterior chamber, and lens parameters may be heritable whereas angle parameters were not. LT and LV may play important roles in the pathogenesis of angle closure. Siblings who are older or have a shallower ACD may need more careful disease monitoring.

WW, PH and C-Terminal Domains Cooperate to Direct the Subcellular Localizations of PLEKHA5, PLEKHA6 and PLEKHA7

PLEKHA5, PLEKHA6, and PLEKHA7 (WW-PLEKHAs) are members of the PLEKHA family of proteins that interact with PDZD11 through their tandem WW domains. WW-PLEKHAs contribute to the trafficking and retention of transmembrane proteins, including nectins, Tspan33, and the copper pump ATP7A, at cell-cell junctions and lateral membranes. However, the structural basis for the distinct subcellular localizations of PLEKHA5, PLEKHA6, and PLEKHA7 is not clear. Here we expressed mutant and chimeric proteins of WW-PLEKHAs in cultured cells to clarify the role of their structural domains in their localization. We found that the WW-mediated interaction between PLEKHA5 and PDZD11 is required for their respective association with cytoplasmic microtubules. The PH domain of PLEKHA5 is required for its localization along the lateral plasma membrane and promotes the lateral localization of PLEKHA7 in a chimeric molecule. Although the PH domain of PLEKHA7 is not required for its localization at the adherens junctions (AJ), it promotes a AJ localization of chimeric proteins. The C-terminal region of PLEKHA6 and PLEKHA7 and the coiled-coil region of PLEKHA7 promote their localization at AJ of epithelial cells. These observations indicate that the localizations of WW-PLEKHAs at specific subcellular sites, where they recruit PDZD11, are the result of multiple cooperative protein-lipid and protein-protein interactions and provide a rational basis for the identification of additional proteins involved in trafficking and sorting of WW-PLEKHAs.

Characteristics of p.Gln368Ter Myocilin Variant and Influence of Polygenic Risk on Glaucoma Penetrance in the UK Biobank

PURPOSE

MYOC (myocilin) mutations account for 3% to 5% of primary open-angle glaucoma (POAG) cases. We aimed to understand the true population-wide penetrance and characteristics of glaucoma among individuals with the most common MYOC variant (p.Gln368Ter) and the impact of a POAG polygenic risk score (PRS) in this population.

DESIGN

Cross-sectional population-based study.

PARTICIPANTS

Individuals with the p.Gln368Ter variant among 77 959 UK Biobank participants with fundus photographs (FPs).

METHODS

A genome-wide POAG PRS was computed, and 2 masked graders reviewed FPs for disc-defined glaucoma (DDG).

MAIN OUTCOME MEASURES

Penetrance of glaucoma.

RESULTS

Two hundred individuals carried the p.Gln368Ter heterozygous genotype, and 177 had gradable FPs. One hundred thirty-two showed no evidence of glaucoma, 45 (25.4%) had probable/definite glaucoma in at least 1 eye, and 19 (10.7%) had bilateral glaucoma. No differences were found in age, race/ethnicity, or gender among groups (P > 0.05). Of those with DDG, 31% self-reported or had International Classification of Diseases codes for glaucoma, whereas 69% were undiagnosed. Those with DDG had higher medication-adjusted cornea-corrected intraocular pressure (IOPcc) (P < 0.001) vs. those without glaucoma. This difference in IOPcc was larger in those with DDG with a prior glaucoma diagnosis versus those not diagnosed (P < 0.001). Most p.Gln368Ter carriers showed IOP in the normal range (≤21 mmHg), although this proportion was lower in those with DDG (P < 0.02) and those with prior glaucoma diagnosis (P < 0.03). Prevalence of DDG increased with each decile of POAG PRS. Individuals with DDG demonstrated significantly higher PRS compared with those without glaucoma (0.37 ± 0.97 vs. 0.01 ± 0.90; P = 0.03). Of those with DDG, individuals with a prior diagnosis of glaucoma had higher PRS compared with undiagnosed individuals (1.31 ± 0.64 vs. 0.00 ± 0.81; P < 0.001) and 27.5 times (95% confidence interval, 2.5-306.6) adjusted odds of being in the top decile of PRS for POAG.

CONCLUSIONS

One in 4 individuals with the MYOC p.Gln368Ter mutation demonstrated evidence of glaucoma, a substantially higher penetrance than previously estimated, with 69% of cases undetected. A large portion of p.Gln368Ter carriers, including those with DDG, have IOP in the normal range, despite similar age. Polygenic risk score increases disease penetrance and severity, supporting the usefulness of PRS in risk stratification among MYOC p.Gln368Ter carriers.

Thioredoxin reductase as a pharmacological target

Thioredoxin reductases (TrxRs) belong to the pyridine nucleotide disulfide oxidoreductase family enzymes that reduce thioredoxin (Trx). The couple TrxR and Trx is one of the major antioxidant systems that control the redox homeostasis in cells. The thioredoxin system, comprised of TrxR, Trx and NADPH, exerts its activities via a disulfide-dithiol exchange reaction. Inhibition of TrxR is an important clinical goal in all conditions in which the redox state is perturbed. The present review focuses on the most critical aspects of the cellular functions of TrxRs and their inhibition mechanisms by metal ions or chemicals, through direct targeting of TrxRs or their substrates or protein interactors. To update the involvement of overactivation/dysfunction of TrxRs in various pathological conditions, human diseases associated with TrxRs genes were critically summarized by publicly available genome-wide association study (GWAS) catalogs and literature. The pieces of evidence presented here justify why TrxR is recognized as one of the most critical clinical targets and the growing current interest in developing molecules capable of interfering with the functions of TrxR enzymes.

Glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. The global prevalence of glaucoma in people aged 40 to 80 years is estimated to be 3.5%. With the growing number and proportion of older persons in the population, it is projected that 111.8 million people will have glaucoma in 2040. Currently available treatments cannot reverse glaucomatous damage to the visual system; however, early diagnosis and treatment can prevent progression of the disease. In most cases, glaucoma is a chronic condition that requires lifelong management. This article reviews the pathophysiology, classification, clinical manifestations, diagnosis, and management of glaucoma.

Updates on Genes and Genetic Mechanisms Implicated in Primary Angle-Closure Glaucoma

Primary angle-closure glaucoma (PACG) is estimated to affect over 30 million people worldwide by 2040 and is highly prevalent in the Asian population. PACG is more severe and carries three times the higher risk of blindness than primary open-angle glaucoma, thus representing a significant public health concern. High heritability and ethnic-specific predisposition to PACG suggest the involvement of genetic factors in disease development. In the recent past, genetic studies have led to the successful identification of several genes and loci associated with PACG across different ethnicities. The precise cellular and molecular roles of these multiple loci in the development and progression of PACG remains to be elucidated. Nonetheless, these studies have significantly increased our understanding of the emerging cellular processes and biological pathways that might provide more significant insights into the disease’s genetic etiology and may be valuable for future clinical applications. This review aims to summarize and update the current knowledge of PACG genetics analysis research.

Clinical characteristics, rates of blindness, and geographic features of PACD in China

OBJECTIVE

To analyze the rates of blindness with the demographics and clinical characteristics of patients with primary angle-closure disease (PACD) to provide a comprehensive epidemiologic reference in China.

METHODS

A retrospective analysis was conducted in the Chinese Glaucoma Study Consortium database, which is a national multicenter glaucoma research alliance of 111 hospitals participating between December 21, 2015 and September 9, 2018. The diagnosis of PACD was made by qualified physicians through examination. Comparison of sex, age, family history, subtypes of PACD, and blindness were analyzed.

RESULTS

A total of 5762 glaucoma patients were included, of which 4588 (79.6%) had PACD. Of PACD patients, 72.1% were female with the sex ratio (F/M) of 2.6, and the average age of patients was 63.8±9.3 years with the majority between 60 and 70 years. Additionally, 30% of these patients had low vision in one eye, 8.8% had low vision in both eyes, 1.7% had blindness in one eye, and 0.3% had blindness in both eyes. There were statistical differences with regards to age between male and female patients with PACD, with male patients being older on average. Primary angle-closure glaucoma was more commonly diagnosed in males (60%) compared to females (35.9%), whereas acute primary angle closure (APAC) was more commonly diagnosed in females (54.3%) compared to males (37.7%). The visual acuity in APAC patients was lower and the rate of low vision and blindness was higher than other subtypes.

CONCLUSION

PACD was the major type of glaucoma in Chinese hospitals. There were more female patients with PACD, mostly between 60 and 70 years old, with higher rates of APAC in women. APAC resulted in the worst visual outcomes of all PACD subtypes.

Acute Angle Closure in Knobloch Syndrome

We report cases of acute angle closure in 2 young highly myopic siblings with Knobloch syndrome. To our knowledge, this is the first report of acute angle closure in Knobloch syndrome. Both patients were homozygous for a likely pathogenic variant in COL18A1. Both responded to treatment with cyclophotocoagulation and remained stable despite declining or being medically unfit for clear lens extraction. We argue that the recent implication of heterozygous mutations in COL18A1 in familial angle closure supports the argument that acute angle closure in these 2 patients was likely to be a thus far unreported feature of Knobloch syndrome. In addition, these cases also support the hypothesis that pathogenic variants in COL18A1 may be a risk factor for acute angle closure.

Molecular Genetics of Glaucoma: Subtype and Ethnicity Considerations

Glaucoma, the world’s leading cause of irreversible blindness, is a complex disease, with differential presentation as well as ethnic and geographic disparities. The multifactorial nature of glaucoma complicates the study of genetics and genetic involvement in the disease process. This review synthesizes the current literature on glaucoma and genetics, as stratified by glaucoma subtype and ethnicity. Primary open-angle glaucoma (POAG) is the most common cause of glaucoma worldwide, with the only treatable risk factor (RF) being the reduction of intraocular pressure (IOP). Genes associated with elevated IOP or POAG risk include: ABCA1, AFAP1, ARHGEF12, ATXN2, CAV1, CDKN2B-AS1, FOXC1, GAS7, GMDS, SIX1/SIX6, TMCO1, and TXNRD2. However, there are variations in RF and genetic factors based on ethnic and geographic differences; it is clear that unified molecular pathways accounting for POAG pathogenesis remain uncertain, although inflammation and senescence likely play an important role. There are similar ethnic and geographic complexities in primary angle closure glaucoma (PACG), but several genes have been associated with this disorder, including MMP9, HGF, HSP70, MFRP, and eNOS. In exfoliation glaucoma (XFG), genes implicated include LOXL1, CACNA1A, POMP, TMEM136, AGPAT1, RBMS3, and SEMA6A. Despite tremendous progress, major gaps remain in resolving the genetic architecture for the various glaucoma subtypes across ancestries. Large scale carefully designed studies are required to advance understanding of genetic loci as RF in glaucoma pathophysiology and to improve diagnosis and treatment options.

Quantification of iris elasticity using acoustic radiation force optical coherence elastography

Careful quantification of the changes in biomechanical properties of the iris can offer insight into the pathophysiology of some ocular diseases. However, to date there has not been much information available regarding this subject because clinical detection for iris elasticity remains challenging. To overcome this limitation, we explore, for the first time to our knowledge, the potential of measuring iris elasticity using acoustic radiation force optical coherence elastography (ARF-OCE). The resulting images and shear wave propagation, as well as the corresponding shear modulus and Young's modulus from ex vivo and in vivo rabbit models confirmed the feasibility of this method. With features of noninvasive imaging, micrometer-scale resolution, high acquisition speed and real-time processing, ARF-OCE is a promising method for reconstruction of iris elasticity and may have great potential to be applied in clinical ophthalmology with further refinement.

Iris stromal cell nuclei deform to more elongated shapes during pharmacologically-induced miosis and mydriasis

Nuclear shape alteration in ocular tissues, which can be used as a metric for overall cell deformation, may also lead to changes in gene expression and protein synthesis that could affect the biomechanics of the tissue extracellular matrix. The biomechanics of iris tissue is of particular interest in the study of primary angle-closure glaucoma. As the first step towards understanding the mutual role of the biomechanics and deformation of the iris on the activity of its constituent stromal cells, we conducted an ex-vivo study in freshly excised porcine eyes. Iris deformation was achieved by activating the constituent smooth muscles of the iris. Pupillary responses were initiated by inducing miosis and mydriasis, and the irides were placed in a fixative, bisected, and sliced into thin sections in a nasal and temporal horizontal orientation. The tissue sections were stained with DAPI for nucleus, and z-stacks were acquired using confocal microscopy. Images were analyzed to determine the nuclear aspect ratio (NAR) using both three-dimensional (3D) reconstructions of the nuclear surfaces as well as projections of the same 3D reconstruction into flat two-dimensional (2D) shapes. We observed that regardless of the calculation method (i.e., one that employed 3D surface reconstructions versus one that employed 2D projected images) the NAR increased in both the miosis group and the mydriasis group. Three-dimensional quantifications showed that NAR increased from 2.52 ± 0.96 in control group to 2.80 ± 0.81 and 2.74 ± 0.94 in the mydriasis and miosis groups, respectively. Notwithstanding the relative convenience in calculating the NAR using the 2D projected images, the 3D reconstructions were found to generate more physiologically realistic values and, thus, can be used in the development of future computational models to study primary angle-closure glaucoma. Since the iris undergoes large deformations in response to ambient light, this study suggests that the iris stromal cells are subjected to a biomechanically active micro-environment during their in-vivo physiological function.

In-depth analysis of eight susceptibility loci of primary angle closure glaucoma in Han Chinese

Primary angle closure glaucoma (PACG) is a multifactorial disease with genetic predisposition. Primary angle closure (PAC) is the early stage of PACG and they share the same anatomical characteristics. We aimed to examine whether the PACG associated-genetic loci identified previously by genome-wide association study (GWAS) were also related to primary angle closure disease (PACD) in Han Chinese. This cross-sectional case-control study consisted of 232 PAC, 264 PACG and 306 controls. Eight single-nucleotide polymorphisms (SNPs) of PACG susceptibility loci within PLEKHA7, COL11A1, PCMTD1-ST18, EPDR1, CHAT, GLIS3, FERMT2, DPM2-FAM102A were genotyped using participants' blood samples. We excluded 3 SNPs for PAC analysis because the data has been reported using the same sample set. Anatomical parameters such as axial length (AL), anterior chamber depth (ACD) and lens thickness (LT) were included as phenotypes for the association analysis. Allelic and genotypic model tests were performed. Three among the eight SNPs were found to be significantly associated with PACG, e.g. PLEKHA7 rs11024102 in additive, dominant and recessive model; and both CHAT rs1258267 and DPM2-FAM102A rs3739821 in dominant model. CHAT rs1258267 showed marginal association with PAC in dominant model. Anatomical parameters were not found to link to the eight SNPs after Bonferroni multiple test correction. Our data suggest that PLEKHA7 and DPM2-FAM102A might exert effect in the late stage of the PACD, while CHAT may play a broad role in both early and late stages of the PACD.

[Genome-wide studies of primary open-angle glaucoma]

The article reviews literature on developmental stages of genome-wide association studies (GWAS) of primary open-angle glaucoma (POAG). This problem is currently developing and one of the most complex in ophthalmology. The article considers main GWAS of POAG and established GWAS-significant polymorphisms associated with the disease. The topic of genome-wide studies of primary open-angle glaucoma will be of certain interest to ophthalmologists, materials on GWAS-significant loci can be used both in the selection of polymorphisms in replicative studies of POAG in various populations of Russia, and to expand ideas about the molecular genetic mechanisms of the development of the disease.

The role of TRPV4 channels in ocular function and pathologies

Transient potential receptor vanilloid 4 (TRPV4) is an ion channel responsible for sensing osmotic and mechanical signals, which in turn regulates calcium signaling across cell membranes. TRPV4 is widely expressed throughout the body, and plays an important role in normal physiological function, as well as different pathologies, however, its role in the eye is not well known. In the eye, TRPV4 is expressed in various tissues, such as the retina, corneal epithelium, ciliary body, and the lens. In this review, we provide an overview on TRPV4 structure, activation, mutations, and summarize the current knowledge of TRPV4 function and signaling mechanisms in various locations throughout the eye, as well as its role in ocular diseases, such as glaucoma and diabetic retinopathy. Based on the available data, we highlight the therapeutic potential of TRPV4 as well as the shortcomings of current research. Finally, we provide future perspectives on the implications of targeting TRPV4 to treat various ocular pathologies.

Association of Single-Nucleotide Polymorphisms in ABCC5 Gene with Primary Angle Closure Glaucoma and the Ocular Biometric Parameters in a Northern Chinese Population

BACKGROUND

The rs1401999 gene in ABCC5 gene was the first locus confirmed by a genome-wide association study (GWAS) to be associated with both anterior chamber depth (ACD) and primary angle closure glaucoma (PACG); however, this locus was of obvious heterogeneity among different populations in the GWAS, and the conclusion has not been further verified by other studies. Therefore, this study was carried out to investigate whether the single-nucleotide polymorphisms (SNPs) in ABCC5 gene are associated with PACG and the ocular biometric parameters ACD and axial length (AL) in samples from northern China.

METHODS

Case-control association study included 500 PACG patients and 720 unrelated controls from northern China, and genotyping was performed for ten SNPs in ABCC5 gene using an improved multiplex ligation detection reaction technique. The association between these SNPs and risk of PACG was estimated by PLINK using a logistic regression model, while the association between genotypes and ocular biometric parameters was performed by SPSS using generalized estimation equation.

RESULTS

An SNP rs4148568 (p = 0.046) and a haplotype TCGGAG (p = 0.0364) in ABCC5 were associated with PACG, and rs4148568 was nominally associated with AL (β = 0.092, p = 0.08).

CONCLUSIONS

The SNP rs4148568 and a haplotype TCGGAG in ABCC5 contribute to PACG in northern Chinese people. In addition, rs4148568 might be associated with the AL, the variant allele of which may have effect of making the AL longer. Further studies are needed to elucidate the exact mechanism of ABCC5 in the progress of PACG.

Evaluation of Primary Angle-Closure Glaucoma Susceptibility Loci for Estimating Angle Closure Disease Severity

PURPOSE

To investigate whether recently identified genetic loci for primary angle-closure glaucoma (PACG) are associated with disease severity.

DESIGN

Case-control study.

PARTICIPANTS

Eight hundred four PACG patients and 943 control participants of Chinese ethnicity from Singapore.

METHODS

The 8 PACG-associated 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) identified from genome-wide association studies were tested for association with disease severity using logistic regression adjusted for age and gender. A P value of 0.006 was set as significant after Bonferroni correction for testing of 8 loci. We also calculated the weighted genetic risk score (GRS) weighted by the estimated individual SNP effect size on PACG calculated as logarithm of the odds ratio (OR). Disease severity was based on the visual field mean deviation (MD) and classified as early to moderate (MD, >-12 dB) and severe (MD, <-20 dB).

MAIN OUTCOME MEASURES

Association of PACG loci with severe disease.

RESULTS

Of the 804 PACG patients, genotyping data were available for 768 individuals and included 436 with mild-to-moderate PACG and 206 with severe PACG. The PACG patients were significantly older (mean age, 64.3 ± 9.1 years vs. 56.4 ± 8.9 years; P < 0.001) and there were proportionately more women compared with control participants (58.4% vs. 49.0%; P < 0.001). Of the 8 loci investigated, we observed significant evidence of association with severe PACG at 1 SNP, namely rs3816415 in EPDR1 (OR, 2.03; 95% confidence interval [CI], 1.49-2.78; P = 1 × 10^-5). A higher-weighted GRS was associated significantly with severe PACG, with an OR of 3.11 (95% CI, 1.95-4.96) comparing the lowest quartile with the highest quartile.

CONCLUSIONS

Our results show that EPDR1 is associated significantly with severe PACG, suggesting that it may predispose patients to more aggressive disease development. Individuals with PACG with a higher GRS were associated with a higher risk of severe PACG.

Evaluation of the genetic association between early-onset primary angle-closure glaucoma and retinitis pigmentosa

Primary angle-closure glaucoma (PACG) and retinitis pigmentosa (RP) can co-occur, but the mechanism of their association is not yet established. The purpose of this study was to investigate the differences in ocular biometry parameters and molecular genetics in patients with PACG with or without RP, and to determine the association between PACG and RP. Patients with early-onset PACG (age of onset <45 years) with or without RP were selected from the glaucoma outpatient department after full ocular examinations by the same glaucoma specialist (LX). Ocular biometry parameters were statistically analyzed. Blood samples were collected from the probands, and genomic DNA was sent out for whole exome sequencing. Variants in 326 selected genes, were extracted from the whole exome sequencing data and filtered using multiple bioinformatics analysis. The 326 genes included 10 PACG-associated genes from two genome wide association studies; 45 genes associated with anterior segment dysgenesis, microcornea, and microphthalmia; and 271 RetNet genes. Potential pathogenic variants (PPV) were obtained and underwent further genotype-phenotype analysis. As a result, a total of 32 probands with early-onset PACG were collected; nine had accompanying RP. No significant differences were noted for ocular biometry parameters between patients with PACG with RP and with PACG alone. Systematic analysis of the variants revealed that 16 of 32 probands (50%) carried PPV in 15 of 326 genes, including 14 RetNet genes and one anterior segment dysgenesis-associated gene. Of these 16 probands with PPV, five (55.56%) were from the group of nine probands with both had PACG and RP and 11 (47.83%) were from the group of 23 probands with PACG alone. Of the 15 genes, five genes, CRB1, COL2A1, RHO, RP1L1, and PAX6, were reported to cause phenotypes including glaucoma. The variants in RetNet genes appeared to be associated with a significant proportion of PACG, especially in probands with both PACG and RP. These findings enrich the phenotype spectrum of RetNet genes and provide clues for genetic screening for glaucoma. Our study suggests a genetic association between PACG and RP, although the cause-effect relationship between them needs further validation.

Coding Variants in HOOK2 and GTPBP3 May Contribute to Risk of Primary Angle Closure Glaucoma

Primary angle closure glaucoma (PACG) is a major cause of blindness worldwide. This study proposed to screen candidate PACG-associated variants in Chinese Han people. Whole exome sequencing was applied to five confirmed PACG patients and two primary angle closure suspect individuals within a PACG-enriched Chinese Han family. A series of bioinformatics analyses were implemented to obtain high-risk single nucleotide variant (SNV) loci for PACG, which were subsequently used for linkage analysis for identifying linkage genome regions. In addition, MassARRAY SNV genotyping was applied to high-risk PACG loci as well as those within linkage regions in another independent cohort including 251 PACG and 251 normal samples to further screen high-confidence SNVs. A total of 27 loci in 19 genes remained after linkage analysis. The 19 genes were significantly enriched in biological processes tightly related to PACG, including retinol metabolism and salmonella infection. Two nonsynonymous SNV loci, rs897804 in exon15 of HOOK2 and rs3745193 in exon7 of GTPBP3, were recognized with higher variant frequency in PACG samples than that in control samples after association analysis of MassARRAY SNV genotyping data. This study sheds new light on the understanding of PACG incidence among Chinese Han people.

Cooperative binding of the tandem WW domains of PLEKHA7 to PDZD11 promotes conformation-dependent interaction with tetraspanin 33

Pleckstrin homology domain–containing A7 (PLEKHA7) is a cytoplasmic protein at adherens junctions that has been implicated in hypertension, glaucoma, and responses to Staphylococcus aureus α-toxin. Complex formation between PLEKHA7, PDZ domain–containing 11 (PDZD11), tetraspanin 33, and the α-toxin receptor ADAM metallopeptidase domain 10 (ADAM10) promotes junctional clustering of ADAM10 and α-toxin–mediated pore formation. However, how the N-terminal region of PDZD11 interacts with the N-terminal tandem WW domains of PLEKHA7 and how this interaction promotes tetraspanin 33 binding to the WW1 domain is unclear. Here, we used site-directed mutagenesis, glutathione S-transferase pulldown experiments, immunofluorescence, molecular modeling, and docking experiments to characterize the mechanisms driving these interactions. We found that Asp-30 of WW1 and His-75 of WW2 interact through a hydrogen bond and, together with Thr-35 of WW1, form a binding pocket that accommodates a polyproline stretch within the N-terminal PDZD11 region. By strengthening the interactions of the ternary complex, the WW2 domain stabilized the WW1 domain and cooperatively promoted the interaction with PDZD11. Modeling results indicated that, in turn, PDZD11 binding induces a conformational rearrangement, which strengthens the ternary complex, and contributes to enlarging a “hydrophobic hot spot” region on the WW1 domain. The last two lipophilic residues of tetraspanin 33, Trp-283 and Tyr-282, were required for its interaction with PLEKHA7. Docking of the tetraspanin 33 C terminus revealed that it fits into the hydrophobic hot spot region of the accessible surface of WW1. We conclude that communication between the two tandem WW domains of PLEKHA7 and the PLEKHA7–PDZD11 interaction modulate the ligand-binding properties of PLEKHA7.

Glaucoma as a Neurodegenerative Disease Caused by Intrinsic Vulnerability Factors

Glaucoma, one of the most common causes of blindness in developing countries today, involves a progressive loss of neural cells in the optic nerve that leads to progressive, irreversible vision loss. Increased intraocular pressure (IOP) presents as a major risk factor for glaucoma, although there exist cases of glaucoma patients with normal IOP that exhibit damage to retinal ganglion cells (RGCs) and the optic nerve. However, treatment approaches have maintained their focus on modifying IOP due to a lack of other modifiable risks factors. Traditional concepts in glaucoma involve the neuronal environment and external effects as a source of causative factors; however, studies have yet to investigate whether the molecular profile of RGCs in glaucoma patients makes them more vulnerable and/or susceptible to external damage. Our hypothesis states that molecular changes at the whole cell, gene expression, and electrophysiological level of the neurons can contribute to their degeneration. Herein, we briefly describe different types of glaucoma and any similarities to different molecular and cellular features of neurodegeneration. To test our hypothesis, we describe human induced pluripotent stem cells (hiPSCs) as a reliable cellular tool to model neurodegenerative aspects of glaucoma to reveal the multiple pathological molecular mechanisms underlying disease development.

Mutations in SPATA13/ASEF2 cause primary angle closure glaucoma

Current estimates suggest 50% of glaucoma blindness worldwide is caused by primary angle-closure glaucoma (PACG) but the causative gene is not known. We used genetic linkage and whole genome sequencing to identify Spermatogenesis Associated Protein 13, SPATA13 (NM_001166271; NP_001159743, SPATA13 isoform I), also known as ASEF2 (Adenomatous polyposis coli-stimulated guanine nucleotide exchange factor 2), as the causal gene for PACG in a large seven-generation white British family showing variable expression and incomplete penetrance. The 9 bp deletion, c.1432_1440del; p.478_480del was present in all affected individuals with angle-closure disease. We show ubiquitous expression of this transcript in cell lines derived from human tissues and in iris, retina, retinal pigment and ciliary epithelia, cornea and lens. We also identified eight additional mutations in SPATA13 in a cohort of 189 unrelated PACS/PAC/PACG samples. This gene encodes a 1277 residue protein which localises to the nucleus with partial co-localisation with nuclear speckles. In cells undergoing mitosis SPATA13 isoform I becomes part of the kinetochore complex co-localising with two kinetochore markers, polo like kinase 1 (PLK-1) and centrosome-associated protein E (CENP-E). The 9 bp deletion reported in this study increases the RAC1-dependent guanine nucleotide exchange factors (GEF) activity. The increase in GEF activity was also observed in three other variants identified in this study. Taken together, our data suggest that SPATA13 is involved in the regulation of mitosis and the mutations dysregulate GEF activity affecting homeostasis in tissues where it is highly expressed, influencing PACG pathogenesis.

Iris and its relevance to angle closure disease: a review

Glaucoma is a leading cause of irreversible visual impairment, and primary angle closure glaucoma (PACG) affects Asians disproportionately. Whereas advances in ocular imaging have identified several anatomical risk factors, our ability to predict PACG still requires considerable improvement. The iris plays a crucial role in the pathophysiology of angle closure disease, either through a mechanical or vascular mechanism. Irises of closed-angle eyes inhibit vastly different structural constituents as compared with those of open-angle eyes, thereby effecting variations in biomechanical properties and iris fluid conductivity. The clinical consequences include a smaller change in iris volume on pupil dilation in closed-angle eyes, thereby bringing the iris and trabecular meshwork closer in apposition. In this review, we summarise the potential role of the iris in the pathogenesis of angle closure disease.