Association of Genetic Variants With Primary Open-Angle Glaucoma Among Individuals With African Ancestry

Association between gene polymorphisms and glaucoma susceptibility among Africans: a systematic review and meta-analysis

PURPOSE

This study sought to analyze the effect of allele mutations and gene functions specific to glaucoma susceptibility among Africans.

METHODS

Potentially relevant studies were retrieved from major bibliographic databases (PubMed, Scopus, and Web of Science). Data were extracted and study-specific estimates were meta-analyzed using various models to obtain pooled results.

RESULTS

A total of 11 studies were included in the study. The studies included a total of 3,191 cases with glaucoma and 3,013 controls across all variants. There is no association between the E396E variants of the myocilin (MYOC) gene and an increased likelihood of susceptibility to POAG (OR: 0.91 [95% CI 0.42 to 1.97]). The R141L variant of the Lysyl Oxidase Like 1 (LOXL1) gene is associated with an approximately 3-fold increased likelihood of susceptibility to exfoliative syndrome/exfoliative glaucoma (XFS/XFG) (OR: 2.68 [95% CI 0.04 to 198.94]). There is no association between the G153D variant of the LOXL1 gene and an increased likelihood of susceptibility to XFS/XFG (OR: 0.42 [95% CI 0.02 to 7.65]). The rs59892895*C variant of the Amyloid Beta Precursor Protein Binding Family B Member 2 (APBB2) is associated with a 34% increased likelihood of susceptibility to POAG (OR: 1.34 [95% CI 1.13 to 1.58]).

CONCLUSION

Although progress has been made in understanding the genetic basis of the pathogenesis of glaucoma, several gene mutations related to glaucoma pathogenesis in Africans are yet to be discovered, especially those associated with the pathogenesis of POAG, the most prevalent glaucoma subtype in Africa.

Socioeconomic and Racial Disparities in Primary Open Angle Glaucoma in the United States

PRCIS

Socioeconomic status is a potentially significant, although difficult to isolate, factor in determining glaucoma severity.

PURPOSE

To analyze the level of glaucoma severity (mild, moderate, or severe) based on demographic factors, including age, gender, ethnicity, insurance profile, and zip code, and to use this data to extrapolate the effect of socioeconomic status (SES) and race on glaucoma severity at the community level in Memphis, TN.

PATIENTS AND METHODS

Totally, 2913 patients from a tertiary care center with 3 clinic locations in Memphis, TN who had been given the diagnosis of primary open angle glaucoma (POAG) through use of the ICD-10 codes for mild (H40.1111, H40.1121, H40.1131), moderate (H40.1112, H40.1122, H40.1132), and severe (H40.1113, H40.1123, H40.1133) POAG between January 2016 and July 2021 were included in this study. Diagnoses were made after a complete glaucoma workup consisting of Snellen visual acuity, applanation IOP measurement, gonioscopy, automated Humphreys visual fields (10-2 and 24-2), and optic nerve OCT. Demographic information, including age, gender, ethnicity, insurance profile, and zip code, was also collected with disease severity for each patient. SES was approximated using zip code-level census poverty data and insurance profiles. Statistical analyses were performed, including descriptive, multivariable ordinal logistic modeling, and stepwise multivariable linear modeling.

RESULTS

Glaucoma severity was shown to increase with poverty rate (OR=1.089, P <0.0071), age (OR=1.030, P <0.0001), male sex (OR=1.374, P <0.0001), and Black race (OR=1.896, P <0.0001). Severity was shown to be decreased in patients with private insurance compared with Medicare (OR=0.895, P <0.093) and those from Shelby County compared with other counties (OR=0.703, P <0.0001).

CONCLUSIONS

Our findings indicate that worsening glaucoma severity was associated with higher poverty rates in our patient population. However, isolating socioeconomic status (SES) as an independent factor influencing the incidence and severity of glaucoma remains challenging, given the strong correlation between race and SES.

Exploring Associations between Race/Ethnicity and Glaucoma Prevalence in a Multicenter Brazilian Study: The ELSA-Brasil

Purpose

Previous research indicates a higher prevalence of glaucoma in Black individuals of African descent. However, the association between race and glaucoma in Brazil's multiracial population remains underexplored. This study examines this association and seeks to identify preventable factors potentially influencing prevalence differences among racial groups in Brazil, should such difference be found.

Methods

Employing a cross-sectional design, data were analyzed from 10,696 participants in the multicenter Brazilian Longitudinal Study of Adult Health (2008-2010) who self-identified their race as White, Black, mixed race (pardo), Asian, or Indigenous and completed an ophthalmological questionnaire including their self-reported glaucoma status (yes or no). Poisson regression was used to estimate prevalence ratios (PRs) with robust SEs and adjustments for sociodemographic characteristics and the presence of diabetes, hypertension, and obesity.

Results

The prevalence of glaucoma was 5.8% in Black (86/1483), 3.8% in mixed race (101/2688), 3.8% in indigenous (4/106), 3.5% in Asian (10/288), and 2.4% in White (145/6131) populations. Compared with Whites, Blacks and mixed-race individuals were younger. Age-adjusted prevalence was 175% higher in Black individuals (PR=2.75, 95% confidence interval [CI]: 2.12, 3.56) and 85% higher in mixed-race individuals (PR=1.85, 95% CI: 1.44, 2.36) compared with Whites. The strength of these associations was reduced in models including the comorbidities of obesity, hypertension, and diabetes, which are more prevalent in Black and mixed-race individuals.

Conclusions

Our results reveal a higher prevalence of self-reported glaucoma in non-White groups, especially among Black and mixed-race individuals. Although causality cannot be conclusively established, our data suggest that the increased prevalence of glaucoma in these groups, compared with their White peers, is partially influenced by preventable health conditions.

Genetic Variants Associated With a History of Glaucoma Surgery in Japanese Patients With Primary Open Angle Glaucoma

PRCIS

The genetic risk score (GRS) of genetic variants associated with intraocular pressure (IOP) elevation, but not those associated with optic nerve vulnerability, was associated with a history of glaucoma surgery in Japanese patients with primary open angle glaucoma (POAG).

OBJECTIVE

To investigate genetic variants associated with a history of glaucoma surgery in Japanese patients with POAG.

METHODS

Japanese patients with POAG (n = 468), including normal tension glaucoma (n = 246) and high tension glaucoma (n = 222), and control subjects (n = 246) were genotyped for 22 genetic variants predisposing to POAG, which can be classified into those associated with IOP elevation (IOP-related genetic variants) and optic nerve vulnerability independent of IOP (optic nerve-related genetic variants). The unweighted and weighted GRSs of 17 IOP-related, 5 optic nerve-related, and all 22 genetic variants were calculated, and the association between the GRS and a history of glaucoma surgery was evaluated.

RESULTS

There was a significant association (odds ratio 1.13 per unweighted GRS, 95% CI: 1.03 to 1.24, P = 0.0093) between IOP-related unweighted GRS and a history of glaucoma surgery. A significant association (odds ratio 1.09 per 0.1 weighted GRS, 95% CI: 1.04 to 1.14, P = 0.00022) was also found between IOP-related weighted GRS and a history of glaucoma surgery. The IOP-related GRS was positively correlated with the need for glaucoma surgery. The mean of IOP-related unweighted and weighted GRS in patients with POAG with a history of glaucoma surgery were significantly higher ( P = 0.013 and P = 0.00031, respectively) than those in patients with POAG without a history of glaucoma surgery.

CONCLUSIONS

IOP-related, but not optic nerve-related, genetic variants were associated with a history of glaucoma surgery in Japanese patients with POAG. These results indicate that IOP elevation induced by IOP-related genetic variants rather than optic nerve vulnerability induced by optic nerve-related genetic variants may play an important role in requiring glaucoma surgery.

Performance of Polygenic Risk Scores for Primary Open-Angle Glaucoma in Populations of African Descent

Importance

Primary open-angle glaucoma (POAG) polygenic risk scores (PRSs) continue to be evaluated in primarily European-ancestry populations despite higher prevalence and worse outcomes in African-ancestry populations.

Objective

To evaluate how established POAG PRSs perform in African-ancestry samples from the Genetics in Glaucoma Patients of African Descent (GIGA), Genetics of Glaucoma in Individuals of African Descent (GGLAD), and Million Veteran Program (MVP) datasets and compare these with European-ancestry samples.

Design, Setting, and Participants

This was a multicenter, cross-sectional study of POAG cases and controls from Tanzania, South Africa, Nigeria, Ghana, and the US. Included were individuals of African descent from South Africa and Tanzania from the GIGA dataset; individuals of African descent from Ghana, Nigeria, and the US from the GGLAD dataset; and individuals of African or European descent from the US in the MVP dataset. Data were analyzed from January 2022 to July 2023.

Exposures

Three PRSs derived from large meta-analyses of European and Asian populations, namely Gharahkhani et al (Gharahkhani PRS), Han et al (Han PRS), and Craig et al (Craig PRS).

Main Outcomes and Measures

Odds ratios (ORs) for POAG risk stratification comparing the highest and lowest quintiles; area under the receiver operating characteristic curve (AUROC), and liability coefficient of determination (R2) for the addition of PRS to a baseline of age, sex, and first 5 principal components.

Results

A total of 11 673 cases and 66 432 controls were included in this study across 7 ancestral groups. Mean (SD) age of the total participants was 76.9 (8.7) years, with 74 304 males (95.1%). The following were included in each dataset: GIGA (663 cases, 476 controls), GGLAD (1471 cases, 1482 controls), and MVP (9559 cases, 64 474 controls). Increases in ORs were found for the highest POAG risk quintile ranging from an OR of 1.68 (95% CI, 1.17-2.43) in Ghanaians to 7.05 (95% CI, 2.73-19.6) in the South African multiple ancestry group (which derives from at least 5 distinct ancestral groups: Khoisan, Bantus, Europeans, Indians, and Southeast Asians) with the Gharahkhani PRS. The Han PRS showed OR increases for the highest POAG risk quintile ranging from 2.27 (95% CI, 1.49-3.47) in African American individuals in the GGLAD dataset to 7.24 (95% CI, 6.47-8.12) in Europeans. The Craig PRS predicted OR increases in the highest quintile for all groups ranging from 1.51 (95% CI, 1.05-2.18) in Ghanaians to 6.31 (95% CI, 5.67-7.04) in Europeans. However, AUROC and R2 increases above baseline were lower for all African-ancestry compared with European-ancestry groups in the 3 tested PRSs.

Conclusions and Relevance

In this cross-sectional study, despite some improvements in OR-based risk stratification using the Gharahkhani PRSs, Han PRSs, and Craig PRSs, consistently lower improvements in AUROC and R2 for African-ancestry compared with European-ancestry groups highlight the need for risk prediction models tailored to diverse populations.

Genetic Risk Stratification of Primary Open-Angle Glaucoma in Japanese Individuals

PURPOSE

To assess the impact of genetic risk estimation for primary open-angle glaucoma (POAG) in Japanese individuals.

DESIGN

Cross-sectional analysis.

PARTICIPANTS

Genetic risk scores (GRSs) were constructed based on a genome-wide association study (GWAS) of POAG in Japanese people. A total of 3625 Japanese individuals, including 1191 patients and 2434 controls (Japanese Tohoku), were used for the model selection. We also evaluated the discriminative accuracy of constructed GRSs in a dataset comprising 1034 patients and 1147 controls (the Japan Glaucoma Society Omics Group [JGS-OG] and the Genomic Research Committee of the Japanese Ophthalmological Society [GRC-JOS]) and 1900 participants from a population-based study (Hisayama Study).

METHODS

We evaluated 2 types of GRSs: polygenic risk scores using the pruning and thresholding procedure and a GRS using variants associated with POAG in the GWAS of the International Glaucoma Genetics Consortium (IGGC). We selected the model with the highest areas under the receiver operating characteristic curve (AUC). In the population-based study, we evaluated the correlations between GRS and ocular measurements.

MAIN OUTCOME MEASURE

Proportion of patients with POAG after stratification according to the GRS.

RESULTS

We found that a GRS using 98 variants, which showed genome-wide significance in the IGGC, showed the best discriminative accuracy (AUC, 0.65). In the Japanese Tohoku, the proportion of patients with POAG in the top 10% individuals was significantly higher than that in the lowest 10% (odds ratio [OR], 6.15; 95% confidence interval [CI], 4.35-8.71). In the JGS-OG and GRC-JOS, we confirmed similar impact of POAG GRS (AUC, 0.64; OR [top vs. bottom decile], 5.81; 95% CI, 3.79-9.01). In the population-based study, POAG prevalence was significantly higher in the top 20% individuals of the GRS compared with the bottom 20% (9.2% vs. 5.0%). However, the discriminative accuracy was low (AUC, 0.56). The POAG GRS was correlated positively with intraocular pressure (r = 0.08: P = 4.0 × 10-4) and vertical cup-to-disc ratio (r = 0.11; P = 4.0 × 10-6).

CONCLUSIONS

The GRS showed moderate discriminative accuracy for POAG in the Japanese population. However, risk stratification in the general population showed relatively weak discriminative performance.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Integrating Genetics in Glaucoma Screening

PRCIS

As additional glaucoma genes are identified and classified, polygenic risk scores will be refined, facilitating early diagnosis and treatment. Ensuring genetic research is equitable to prevent glaucoma blindness worldwide is crucial.

PURPOSE

To review the progress in glaucoma genetics over the past 25 years, including the identification of genes with varying contributions to the disease and the development of polygenic risk scores.

METHODS/RESULTS

Over the last 2 and a half decades, glaucoma genetics has evolved from identifying genes with Mendelian inheritance patterns, such as myocilin and CYP1B1, to the discovery of hundreds of genes associated with the disease. Polygenic risk scores have been developed, primarily based on research in Northern European populations, and efforts to refine these scores are ongoing. However, there is a question regarding their applicability to other ethnic groups, especially those at higher risk of primary open angle glaucoma, like individuals of African ancestry. Glaucoma is highly heritable and family history can be used for cascade clinical screening programs, but these will not be feasible in all populations. Thus, cascade genetic testing using well-established genes such as myocilin may help improve glaucoma diagnosis. In addition, ongoing investigations seek to identify pathogenic genetic variants within genes like myocilin.

CONCLUSIONS

The expanding availability of genetic testing for various diseases and early access to genetic risk information necessitates further research to determine when and how to act on specific genetic results. Polygenic risk scores involving multiple genes with subtle effects will require continuous refinement to improve clinical utility. This is crucial for effectively interpreting an individual's risk of developing glaucoma and preventing blindness.

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.

A multi-cohort genome-wide association study in African ancestry individuals reveals risk loci for primary open-angle glaucoma

Primary open-angle glaucoma (POAG), the leading cause of irreversible blindness worldwide, disproportionately affects individuals of African ancestry. We conducted a genome-wide association study (GWAS) for POAG in 11,275 individuals of African ancestry (6,003 cases; 5,272 controls). We detected 46 risk loci associated with POAG at genome-wide significance. Replication and post-GWAS analyses, including functionally informed fine-mapping, multiple trait co-localization, and in silico validation, implicated two previously undescribed variants (rs1666698 mapping to DBF4P2; rs34957764 mapping to ROCK1P1) and one previously associated variant (rs11824032 mapping to ARHGEF12) as likely causal. For individuals of African ancestry, a polygenic risk score (PRS) for POAG from our mega-analysis (African ancestry individuals) outperformed a PRS from summary statistics of a much larger GWAS derived from European ancestry individuals. This study quantifies the genetic architecture similarities and differences between African and non-African ancestry populations for this blinding disease.

Genomics enabling personalised glaucoma care

Glaucoma is a leading cause of visual impairment and a significant public health concern, but despite ongoing advances in our understanding of the disease, several important clinical challenges remain. With the number of affected people projected to increase substantially over coming decades, novel approaches to screening, risk stratification, therapy and glaucoma research are essential to deal with this expanding burden in an efficient and cost-effective manner. Genomics may hold the key to unlocking further biological insights and enabling precision medicine, in which glaucoma care is tailored to the individual patient, based on their unique profile for disease. Here, we provide an overview of how genomics may enable cost-effective targeted population screening and personalised predictions of risk, response to treatment and effective lifestyle advice. Given rapid advances in genetic testing technology and a move towards population-level genotyping, these early results have several important implications that promise to revolutionise the way in which glaucoma is detected and managed in years to come.

Sex and Race Differences in Obesity-Related Genetic Susceptibility and Risk of Cardiometabolic Disease in Older US Adults

Importance

The fat mass and obesity-associated gene (FTO) is associated with obesity phenotypes, but the association is inconsistent across populations. Within-population differences may explain some of the variability observed.

Objective

To investigate sex differences in the association between FTO single-nucleotide variants (SNVs) and obesity traits among self-identified non-Hispanic Black and non-Hispanic White US adults, to examine whether the SNVs were associated with cardiometabolic diseases, and to evaluate whether obesity mediated the association between FTO SNVs and cardiometabolic diseases.

Design, Setting, and Participants

This cross-sectional study used data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a US population-based cohort study with available genetic data (assayed in 2018) and phenotypic data at baseline (enrolled 2003-2007). Participants were aged 45 to 98 years at baseline. Data were analyzed from October 2021 to October 2022.

Exposures

Eleven SNVs in the FTO gene present among both Black and White participants.

Main Outcomes and Measures

Objectively measured obesity indicators (body mass index and waist-to-height ratio), objectively measured and/or self-reported cardiometabolic diseases (hypertension, stroke history, heart disease, and diabetes), and self-reported social-economic and psychosocial status.

Results

A total of 10 447 participants (mean [SD] age, 64.4 [9.7] years; 5276 [55.8%] women; 8743 [83.7%] Black and 1704 [16.3%] White) were included. In the White group, 11 FTO SNVs were significantly associated with obesity, hypertension, and diabetes using linear models (eg, body mass index: β = 0.536; 95% CI, 0.197-0.875), but none of the FTO SNVs were associated with obesity traits in the Black group. White males had a higher risk of obesity while White females had a higher risk of hypertension and diabetes. However, 1 FTO SNV (rs1121980) was associated with a direct increase in the risk of heart disease in Black participants not mediated by obesity (c' = 0.145 [SE, 0.0517]; P = .01).

Conclusions and Relevance

In this cross-sectional study of obesity phenotypes and their association with cardiometabolic diseases, the tested FTO SNVs reflected sex differences in White participants. Different patterns of associations were observed among self-identified Black participants. Therefore, these results could inform future work discovering risk alleles or risk scores unique to Black individuals or further investigating genetic risk in all US residents.

Phenotypic expressions of the optic disc in primary open-angle glaucoma

BACKGROUND

Which phenotypes are we able to recognize in the optic nerve of patients with primary open angle glaucoma?

METHODS

Retrospective interventional case series. 885 eyes from 885 patients at an outpatient tertiary care centre who met specified criteria for POAG were included. Disc photographs were classified by three glaucoma specialists into the following phenotypes according to their predominant characteristics: (1) concentric rim thinning, (2) focal rim thinning, (3) acquired pit of the optic nerve (APON), (4) tilted, (5) extensive peripapillary atrophy (PPA), and (6) broad rim thinning. Demographic, medical, and ocular data were collected. Kruskal-Wallis was used as a non-parametric test and pairwise comparison was performed by using Wilcoxon rank sum test corrected.

RESULTS

Phenotypic distribution was as follows: 398(45%) focal thinning, 153(18%) concentric thinning, 153(17%) broad thinning, 109(12%) tilted, 47(5%) extensive PPA and 25(3%) APON. Phenotypic traits of interest included a higher proportion of female patients with the focal thinning phenotype (p = 0.015); myopia (p = 0.000), Asian race (OR: 8.8, p = 0.000), and younger age (p = 0.000) were associated with the tilted phenotype; the concentric thinning patients had thicker RNFL (p = 0.000), higher MD (p = 0.008) and lower PSD (p = 0.043) than broad thinning, despite no difference in disc sizes (p = 0.849). The focal thinning group had a localized VF pattern with high PSD compared to concentric thinning (p = 0.005).

CONCLUSION

We report six phenotypic classifications of POAG patients with demographic and ocular differences between phenotypes. Future refinement of phenotypes should allow enhanced identification of genetic associations and improved individualization of patient care.

Understanding the complex genetics and molecular mechanisms underlying glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. Currently the only effective treatment for glaucoma is to reduce the intraocular pressure, which can halt the progression of the disease. Highlighting the importance of identifying individuals at risk of developing glaucoma and those with early-stage glaucoma will help patients receive treatment before sight loss. However, some cases of glaucoma do not have raised intraocular pressure. In fact, glaucoma is caused by a variety of different mechanisms and has a wide range of different subtypes. Understanding other risk factors, the underlying mechanisms, and the pathology of glaucoma might lead to novel treatments and treatment of underlying diseases. In this review we present the latest research into glaucoma including the genetics and molecular basis of the disease.

WITHDRAWN: Genome-wide risk prediction of primary open-angle glaucoma across multiple ancestries

This manuscript has been withdrawn by medRxiv following a formal request by the QIMR Berghofer Medical Research Institute Research Integrity Office owing to lack of author consent.

Determinants of participation in glaucoma genomic research in South East Nigeria: A cross-sectional analytical study

BACKGROUND

Genomic research advances the understanding of human health and disease. It also drives both the discovery of salient genetic association(s) as well as targeted screening, diagnostic and therapeutic strategies. Human subject participation is crucial for the success of genomic research.

METHODS

This is a cross sectional analytical study conducted at two tertiary centers in Enugu Southeast Nigeria. Semi structured questionnaires were administered to eligible consenting participants. Data on their demographics, willingness to participate in genomic research and motivation for participation were obtained. Data was analyzed using Stata version 17 and summarized using median, frequencies and interquartile range(IQR). Associations between covariates were evaluated with Chi square test and multivariable logistic regression.

RESULTS

Among 228 glaucoma subjects who participated in our study,119(52.2%) were female and 109(47.8%) were male. The median age was 64 years(IQR = 50-76). Although 219 (96.0%) participants expressed willingness to participate in a glaucoma genetic study, only 27(11.9%) of them will be willing to participate if there will not be feedback of results to participants (χ2 = 18.59, P<0.001). No participant expressed willingness to submit ocular tissue samples. Majority (96.2%) of subjects will not participate if the intended research required submission of body samples after death. Desire to know more about glaucoma (63%) was the most common reason for participation. In a multivariable logistic model, subjects between 61-90 years (p = 0.004, OR = 7.2) were 7 times more likely to express willingness to participate in glaucoma genetic research after adjusting for other covariates when compared to subjects aged 41-60 years. Other covariates did not influence participants' willingness.

CONCLUSION

Glaucoma subjects are more likely to be willing to participate in genetic research, if they would receive feedback of results. Willingness to participate in genetic research is significantly associated with age.

LIMITATIONS

We did not evaluate the salient options for feedback of results to participants in our study.

Glaucoma in Black Individuals: How Far Have We Come and Where Do We Go From Here?

PURPOSE

To provide updates on the key scientific discoveries made and sociological theories put forth that have allowed for a better understanding of the disproportionate burden of glaucoma among Black individuals, and to provide insights into future directions for this important field of work.

DESIGN

Perspective with a scoping review of the literature.

METHODS

Review, synthesis, and critical appraisal of selected literature on the impact of glaucoma in Black Americans. Important studies within and outside of ophthalmology are considered to allow for a greater understanding of the historical, sociopolitical, and encompassing medical contexts surrounding this complex issue.

RESULTS

A historical overview of key epidemiologic studies highlights the repeated and unequivocal demonstration of increased risk of glaucoma in Black individuals. To begin to understand this multi-layered racial disparity, a historical review of race as a social-legal construct is provided. A careful examination of genetic ancestry is considered as a partial means by which increased glaucoma risk is conferred among Black individuals. The growing body of work examining social determinants as an important driver for racial disparities in glaucoma is also reviewed. Finally, the pitfalls and dangers of race-based medicine are highlighted through illustrative cases before providing insights to future directions.

CONCLUSIONS

Though our understanding of the disparities in glaucoma in Black individuals has grown over the past decades, gaps persist, particularly due to deficient data driven by a lack of studies in this disproportionately burdened group. Though the use of race as a variable may become increasingly less relevant with the rise of precision medicine, it remains a crucial, though flawed concept that continues to be our best means by which to measure, investigate, and intervene upon these disparities in our efforts to achieve health equity.

Identifying, Understanding, and Addressing Disparities in Glaucoma Care in the United States

Glaucoma is the leading cause of irreversible blindness worldwide, currently affecting around 80 million people. Glaucoma prevalence is rapidly rising in the United States due to an aging population. Despite recent advances in the diagnosis and treatment of glaucoma, significant disparities persist in disease detection, management, and outcomes among the diverse patient populations of the United States. Research on disparities is critical to identifying, understanding, and addressing societal and healthcare inequalities. Disparities research is especially important and impactful in the context of irreversible diseases such as glaucoma, where earlier detection and intervention are the primary approach to improving patient outcomes. In this article, we first review recent studies identifying disparities in glaucoma care that affect patient populations based on race, age, and gender. We then review studies elucidating and furthering our understanding of modifiable factors that contribute to these inequities, including socioeconomic status (particularly age and education), insurance product, and geographic region. Finally, we present work proposing potential strategies addressing disparities in glaucoma care, including teleophthalmology and artificial intelligence. We also discuss the presence of non-modifiable factors that contribute to differences in glaucoma burden and can confound the detection of glaucoma disparities.

Translational Relevance

By recognizing underlying causes and proposing potential solutions, healthcare providers, policymakers, and other stakeholders can work collaboratively to reduce the burden of glaucoma and improve visual health and clinical outcomes in vulnerable patient populations.

Association of Rates of Ganglion Cell and Inner Plexiform Thinning With Development of Glaucoma in Eyes With Suspected Glaucoma

Importance

In eyes with suspected glaucoma, it is clinically relevant to find diagnostic tests for the risk of development of perimetric glaucoma.

Objective

To investigate the association between rates of ganglion cell/inner plexiform layer (GCIPL) and circumpapillary retinal nerve fiber layer (cpRNFL) thinning and the development of perimetric glaucoma in eyes with suspected glaucoma.

Design, Setting, and Participants

This observational cohort study used data collected in December 2021 from a tertiary center study and a multicenter study. Participants with suspected glaucoma were followed up for 3.1 years. The study was designed in December 2021 and finalized in August 2022.

Exposures

Development of perimetric glaucoma was defined as having 3 consecutive results showing abnormal visual fields. Using linear mixed-effect models, rates of GCIPL were compared between eyes with suspected glaucoma that did and did not develop perimetric glaucoma. A joint longitudinal multivariable survival model was used to investigate the performance of rates of GCIPL and cpRNFL thinning in predicting the risk of developing perimetric glaucoma.

Main Outcomes and Measures

Rates of GCIPL thinning and hazard ratio (HR) of developing perimetric glaucoma.

Results

Among a total of 462 participants, the mean (SD) age was 63.3 (11.1) years, and 275 patients (60%) were female. Of 658 eyes, 153 eyes (23%) developed perimetric glaucoma. The mean rates of GCIPL thinning were faster in eyes that developed perimetric glaucoma (-1.28 vs -0.66 μm/y for minimum GCIPL thinning; difference, -0.62; 95% CI, -1.07 to -0.16; P = .02). Based on the joint longitudinal survival model, every 1-μm/y faster rate of minimum GCIPL and rate of global cpRNFL thinning were associated with a 2.4 and 1.9 higher risk of developing perimetric glaucoma, respectively (HR, 2.4; 95% CI, 1.8 to 3.2, and HR, 1.99; 95% CI, 1.76 to 2.22, respectively; P < .001). Among the predictive factors, African American race (HR, 1.56; 95% CI, 1.05 to 2.34; P = .02), male sex (HR, 1.47; 95% CI, 1.02 to 2.15; P = .03), 1-dB higher baseline visual field pattern standard deviation (HR, 1.73; 95% CI, 1.56 to 1.91; P < .001), and 1-mm Hg higher mean intraocular pressure during follow-up (HR, 1.11; 95% CI, 1.05 to 1.17; P < .001) were associated with higher risk of developing perimetric glaucoma.

Conclusions and Relevance

This study found that faster rates of GCIPL and cpRNFL thinning were associated with higher risks of developing perimetric glaucoma. Rates of cpRNFL thinning and specifically GCIPL thinning may be useful measures for monitoring eyes with suspected glaucoma.

Reverse translation of artificial intelligence in glaucoma: Connecting basic science with clinical applications

Artificial intelligence (AI) has been approved for biomedical research in diverse areas from bedside clinical studies to benchtop basic scientific research. For ophthalmic research, in particular glaucoma, AI applications are rapidly growing for potential clinical translation given the vast data available and the introduction of federated learning. Conversely, AI for basic science remains limited despite its useful power in providing mechanistic insight. In this perspective, we discuss recent progress, opportunities, and challenges in the application of AI in glaucoma for scientific discoveries. Specifically, we focus on the research paradigm of reverse translation, in which clinical data are first used for patient-centered hypothesis generation followed by transitioning into basic science studies for hypothesis validation. We elaborate on several distinctive areas of research opportunities for reverse translation of AI in glaucoma including disease risk and progression prediction, pathology characterization, and sub-phenotype identification. We conclude with current challenges and future opportunities for AI research in basic science for glaucoma such as inter-species diversity, AI model generalizability and explainability, as well as AI applications using advanced ocular imaging and genomic data.

Diversity in Polygenic Risk of Primary Open-Angle Glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. Primary open-angle glaucoma (POAG), the most common glaucoma subtype, is more prevalent and severe in individuals of African ancestry. Unfortunately, this ancestral group has been historically under-represented among genetic studies of POAG. Moreover, both genetic and polygenic risk scores (GRS, PRS) that are typically based on genetic data from European-descent populations are not transferable to individuals without a majority of European ancestry. Given the aspirations of leveraging genetic information for precision medicine, GRS and PRS demonstrate clinical potential but fall short, in part due to the lack of diversity in these studies. Prioritizing diversity in the discovery of risk variants will improve the performance and utility of GRS and PRS-derived risk estimation for disease stratification, which could bring about earlier POAG intervention and treatment for a disease that often goes undetected until significant damage has occurred.

Genetic variants associated with glaucomatous visual field loss in primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is characterized by a progressive optic neuropathy with visual field loss. To investigate the genetic variants associated with visual field loss in POAG, Japanese POAG patients (n = 426) and control subjects (n = 246) were genotyped for 22 genetic variants predisposing to POAG that can be classified into those associated with intraocular pressure (IOP) elevation (IOP-related genetic variants) and optic nerve vulnerability independent of IOP (optic nerve-related genetic variants). The genetic risk score (GRS) of the 17 IOP-related and five optic nerve-related genetic variants was calculated, and the associations between the GRS and the mean deviation (MD) of automated static perimetry as an indicator of the severity of visual field loss and pattern standard deviation (PSD) as an indicator of the focal disturbance were evaluated. There was a significant association (Beta = - 0.51, P = 0.0012) between the IOP-related GRS and MD. The severity of visual field loss may depend on the magnitude of IOP elevation induced by additive effects of IOP-related genetic variants. A significant association (n = 135, Beta = 0.65, P = 0.0097) was found between the optic nerve-related, but not IOP-related, GRS and PSD. The optic nerve-related (optic nerve vulnerability) and IOP-related (IOP elevation) genetic variants may play an important role in the focal and diffuse visual field loss respectively. To our knowledge, this is the first report to show an association between additive effects of genetic variants predisposing to POAG and glaucomatous visual field loss, including severity and focal/diffuse disturbance of visual field loss, in POAG.

The social construction of genomics and genetic analysis in ocular diseases in Ibadan, South-western Nigeria

Genomics, an emerging field to improve public health practice, has potential benefits to understanding ocular diseases. This study explored the social construction of genomics in ocular diseases in the blind community in Ibadan, Nigeria, through two focus group discussions and twelve in-depth interview sessions conducted among people living with ocular disorders. The data were thematic and content-analysed. Although the participants had limited knowledge about ocular diseases, genomics, and their nexus, they maintained a positive attitude toward its potential benefits. This informed their willingness to participate in genomics testing for ocular diseases. The participants preferred saliva-based sample collection over blood-based, and expressed concern for the procedure and accrued benefits of genomics studies. Thus, public sensitisation about ocular diseases and client-centred genomics testing procedures should be engendered.

Development and Evaluation of a Rules-based Algorithm for Primary Open-Angle Glaucoma in the VA Million Veteran Program

The availability of electronic health record (EHR)-linked biobank data for research presents opportunities to better understand complex ocular diseases. Developing accurate computable phenotypes for ocular diseases for which gold standard diagnosis includes imaging remains inaccessible in most biobank-linked EHRs. The objective of this study was to develop and validate a computable phenotype to identify primary open-angle glaucoma (POAG) through accessing the Department of Veterans Affairs (VA) Computerized Patient Record System (CPRS) and Million Veteran Program (MVP) biobank. Accessing CPRS clinical ophthalmology data from VA Medical Center Eye Clinic (VAMCEC) patients, we developed and iteratively refined POAG case and control algorithms based on clinical, prescription, and structured diagnosis data (ICD-CM codes). Refinement was performed via detailed chart review, initially at a single VAMCEC (n = 200) and validated at two additional VAMCECs (n = 100 each). Positive and negative predictive values (PPV, NPV) were computed as the proportion of CPRS patients correctly classified with POAG or without POAG, respectively, by the algorithms, validated by ophthalmologists and optometrists with access to gold-standard clinical diagnosis data. The final algorithms performed better than previously reported approaches in assuring the accuracy and reproducibility of POAG classification (PPV >83% and NPV >97%) with consistent performance in Black or African American and in White Veterans. Applied to the MVP to identify cases and controls, genetic analysis of a known POAG-associated locus further validated the algorithms. We conclude that ours is a viable approach to use combined EHR-genetic data to study patients with complex diseases that require imaging confirmation.

Glaucoma Genetic Risk Scores in the Million Veteran Program

PURPOSE

Primary open-angle glaucoma (POAG) is a degenerative eye disease for which early treatment is critical to mitigate visual impairment and irreversible blindness. POAG-associated loci individually confer incremental risk. Genetic risk score(s) (GRS) could enable POAG risk stratification. Despite significantly higher POAG burden among individuals of African ancestry (AFR), GRS are limited in this population. A recent large-scale, multi-ancestry meta-analysis identified 127 POAG-associated loci and calculated cross-ancestry and ancestry-specific effect estimates, including in European ancestry (EUR) and AFR individuals. We assessed the utility of the 127-variant GRS for POAG risk stratification in EUR and AFR Veterans in the Million Veteran Program (MVP). We also explored the association between GRS and documented invasive glaucoma surgery (IGS).

DESIGN

Cross-sectional study.

PARTICIPANTS

MVP Veterans with imputed genetic data, including 5830 POAG cases (445 with IGS documented in the electronic health record) and 64 476 controls.

METHODS

We tested unweighted and weighted GRS of 127 published risk variants in EUR (3382 cases and 58 811 controls) and AFR (2448 cases and 5665 controls) Veterans in the MVP. Weighted GRS were calculated using effect estimates from the most recently published report of cross-ancestry and ancestry-specific meta-analyses. We also evaluated GRS in POAG cases with documented IGS.

MAIN OUTCOME MEASURES

Performance of 127-variant GRS in EUR and AFR Veterans for POAG risk stratification and association with documented IGS.

RESULTS

GRS were significantly associated with POAG (P < 5 × 10-5) in both groups; a higher proportion of EUR compared with AFR were consistently categorized in the top GRS decile (21.9%-23.6% and 12.9%-14.5%, respectively). Only GRS weighted by ancestry-specific effect estimates were associated with IGS documentation in AFR cases; all GRS types were associated with IGS in EUR cases.

CONCLUSIONS

Varied performance of the GRS for POAG risk stratification and documented IGS association in EUR and AFR Veterans highlights (1) the complex risk architecture of POAG, (2) the importance of diverse representation in genomics studies that inform GRS construction and evaluation, and (3) the necessity of expanding diverse POAG-related genomic data so that GRS can equitably aid in screening individuals at high risk of POAG and who may require more aggressive treatment.

Genome-Wide Association Study Identifies Two Common Loci Associated with Pigment Dispersion Syndrome/Pigmentary Glaucoma and Implicates Myopia in its Development

PURPOSE

To identify genetic variants associated with pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG) in unrelated patients and to further understand the genetic and potentially causal relationships between PDS and associated risk factors.

DESIGN

A 2-stage genome-wide association meta-analysis with replication and subsequent in silico analyses including Mendelian randomization.

PARTICIPANTS

A total of 574 cases with PG or PDS and 52 627 controls of European descent.

METHODS

Genome-wide association analyses were performed in 4 cohorts and meta-analyzed in 3 stages: (1) a discovery meta-analysis was performed in 3 cohorts, (2) replication was performed in the fourth cohort, and (3) all 4 cohorts were meta-analyzed to increase statistical power. Two-sample Mendelian randomization was used to determine whether refractive error and intraocular pressure exert causal effects over PDS.

MAIN OUTCOME MEASURES

The association of genetic variants with PDS and whether myopia exerts causal effects over PDS.

RESULTS

Significant association was present at 2 novel loci for PDS/PG. These loci and follow-up analyses implicate the genes gamma secretase activator protein (GSAP) (lead single nucleotide polymorphism [SNP]: rs9641220, P = 6.0×10-10) and glutamate metabotropic receptor 5 (GRM5)/TYR (lead SNP: rs661177, P = 3.9×10-9) as important factors in disease risk. Mendelian randomization showed significant evidence that negative refractive error (myopia) exerts a direct causal effect over PDS (P = 8.86×10-7).

CONCLUSIONS

Common SNPs relating to the GSAP and GRM5/TYR genes are associated risk factors for the development of PDS and PG. Although myopia is a known risk factor, this study uses genetic data to demonstrate that myopia is, in part, a cause of PDS and PG.

The Predictive Values of Changes in Local and Remote Brain Functional Connectivity in Primary Angle-Closure Glaucoma Patients According to Support Vector Machine Analysis

Purpose

The primary angle-closure glaucoma (PACG) is an irreversible blinding eye disease in the world. Previous neuroimaging studies demonstrated that PACG patients were associated with cerebral changes. However, the effect of optic atrophy on local and remote brain functional connectivity in PACG patients remains unknown.

Materials and Methods

In total, 23 patients with PACG and 23 well-matched Health Controls (HCs) were enrolled in our study and underwent resting-state functional magnetic resonance imaging (rs-fMRI) scanning. The regional homogeneity (ReHo) method and functional connectivity (FC) method were used to evaluate the local and remote brain functional connectivity. Moreover, support vector machine (SVM) method was applied to constructing PACG classification model.

Results

Compared with the HC, PACG patients showed increased ReHo values in right cerebellum (CER)_8, left CER_4-5, and right CER_8. In contrast, PACG patients showed decreased ReHo values in the bilateral lingual gyrus (LING)/calcarine (CAL)/superior occipital gyrus (SOG) and right postcentral gyrus (PostCG). The ReHo value exhibited an accuracy of 91.30% and area under curve (AUC) of 0.95 for distinguishing the PACG patients from HC.

Conclusion

Our study demonstrated that the PACG patients showed abnormal ReHo value in the cerebellum, visual cortex, and supplementary motor area, which might be reflect the neurological mechanisms underlying vision loss and eye pain in PACG patients. Moreover, the ReHo values can be used as a useful biomarker for distinguishing the PACG patients from HCs.

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.

Prevalence Rates and Risk Factors for Primary Open Angle Glaucoma in the Middle East

Glaucoma is a multifactorial disease and a leading cause of irreversible blindness worldwide. Current data has demonstrated the approximate distribution of primary open-angle glaucoma (POAG) in patients of European, African, Hispanic, and Eastern Asian descent. However, a significant gap in the literature exists regarding the prevalence of POAG in Middle Eastern (ME) populations. Current studies estimate ME POAG prevalence based on a European model. Herein we screened 65 total publications on ME prevalence of POAG and specific risk factors using keywords: "glaucoma", "prevalence", "incidence", "risk factor", "Middle East", "Mideast", "Persian", "Far East", as well as searching by individual ME countries through PubMed, Embase, Ovid, Scopus, and Trip searches with additional reference list searches from relevant articles published up to and including March 1, 2021. Fifty qualifying records were included after 15 studies identified with low statistical power, confounding co-morbid ophthalmic diseases, and funding bias were excluded. Studies of ME glaucoma risk factors that identify chromosomes, familial trend, age/gender, socioeconomic status, lifestyle, intraocular pressure, vascular influences, optic disc hemorrhage, cup-to-disc ratio, blood pressure, obstructive sleep apnea, and diabetes mellitus were included in this systematic review. We conclude that the prevalence of POAG in the ME is likely higher than the prevalence rate that European models suggest, with ME specific risk factors likely playing a role. However, these findings are severely limited by the paucity of population-level data in the ME. Well-designed, longitudinal population-based studies with rigorous inclusion and exclusion criteria are ultimately needed to accurately assess the epidemiology and specific mechanistic risk factors of glaucoma in ME populations.

Lack of Association Between Polymorphisms in TXNRD2 and LMX1B and Primary Open-Angle Glaucoma in a Saudi Cohort

Objective: Recent studies have demonstrated an association of single nucleotide polymorphisms (SNPs) rs35934224 in TXNRD2 and rs6478746 near LMX1B genes in primary open-angle glaucoma (POAG) among Europeans. We performed a retrospective, case-control study to investigate the association between the rs35934224 (TXNRD2) and rs6478746 (LMX1B) and POAG in a middle-eastern population from Saudi Arabia. Methods: DNA from 399 participants consisting of 150 POAG cases (83 males and 67 females) and 249 controls (135 males and 114 females) were genotyped using TaqMan® real-time PCR. Statistical tests were performed to evaluate genetic association with POAG and related clinical indices. Results: The minor allele frequency (MAF) of rs35934224[T] was 0.19 and 0.20 in POAG and controls, respectively. The difference was non-significant (odds ratio [OR] = 1.08, 95% confidence interval [CI] = 0.75-1.55, p = 0.663). Likewise, rs6478746[G] MAF was 0.12 in both cases and controls with no statistical significance (OR = 1.02, 95% CI = 0.67-1.56, p = 0.910). Genotype analysis showed no association with POAG for both the SNPs in combined and gender-stratified groups. Regression analysis showed no significant effect of risk factors such as age, sex, rs35934224, and rs6478746 genotypes on POAG outcome. Furthermore, both the SNPs showed no significant genotype effect on clinical indices such as intraocular pressure (IOP) and cup/disc ratio in POAG patients. Conclusions: Rs35934224 in TXNRD2 and rs6478746 near LMX1B genes are not associated with POAG or related clinical indices such as IOP and cup/disc ratio in a Saudi cohort. Since the study is limited by sample size further investigations are needed to confirm these results in a larger cohort.

Population screening for glaucoma in UK: current recommendations and future directions

Effective population screening for glaucoma would enable earlier diagnosis and prevention of irreversible vision loss. The UK National Screening Committee (NSC) recently published a review that examined the viability, effectiveness and appropriateness of a population-based screening programme for primary open-angle glaucoma (POAG). In our article, we summarise the results of the review and discuss some future directions that may enable effective population screening for glaucoma in the future. Two key questions were addressed by the UK NSC review; is there a valid, accurate screening test for POAG, and does evidence exist that screening reduces morbidity from POAG compared with standard care. Six new studies were identified since the previous 2015 review. The review concluded that screening for glaucoma in adults is not recommended because there is no clear evidence for a sufficiently accurate screening test or for better outcomes with screening compared to current care. The next UK NSC review is due to be conducted in 2023. One challenge for POAG screening is that the relatively low disease prevalence results in too many false-positive referrals, even with an accurate test. In the future, targeted screening of a population subset with a higher prevalence of glaucoma may be effective. Recent developments in POAG polygenic risk prediction and deep learning image analysis offer potential avenues to identifying glaucoma-enriched sub-populations. Until such time, opportunistic case finding through General Ophthalmic Services remains the primary route for identification of glaucoma in the UK and greater public awareness of the service would be of benefit.

Eyes of Africa: The Genetics of Blindness: Study Design and Methodology

BACKGROUND

This report describes the design and methodology of the "Eyes of Africa: The Genetics of Blindness," a collaborative study funded through the Human Heredity and Health in Africa (H3Africa) program of the National Institute of Health.

METHODS

This is a case control study that is collecting a large well phenotyped data set among glaucoma patients and controls for a genome wide association study. (GWAS). Multiplex families segregating Mendelian forms of early-onset glaucoma will also be collected for exome sequencing.

DISCUSSION

A total of 4500 cases/controls have been recruited into the study at the end of the 3rd funded year of the study. All these participants have been appropriately phenotyped and blood samples have been received from these participants. Recent GWAS of POAG in African individuals demonstrated genome-wide significant association with the APBB2 locus which is an association that is unique to individuals of African ancestry. This study will add to the existing knowledge and understanding of POAG in the African population.

Risk Stratification and Clinical Utility of Polygenic Risk Scores in Ophthalmology

Translational Relevance

Common genetic variants can be used to effectively stratify the risk of disease development and progression and may be used to guide screening, triaging, monitoring, or treatment thresholds.

African genetic diversity and adaptation inform a precision medicine agenda

The deep evolutionary history of African populations, since the emergence of modern humans more than 300,000 years ago, has resulted in high genetic diversity and considerable population structure. Selected genetic variants have increased in frequency due to environmental adaptation, but recent exposures to novel pathogens and changes in lifestyle render some of them with properties leading to present health liabilities. The unique discoverability potential from African genomic studies promises invaluable contributions to understanding the genomic and molecular basis of health and disease. Globally, African populations are understudied, and precision medicine approaches are largely based on data from European and Asian-ancestry populations, which limits the transferability of findings to the continent of Africa. Africa needs innovative precision medicine solutions based on African data that use knowledge and implementation strategies aligned to its climatic, cultural, economic and genomic diversity.

Predicting the Future of Genetic Risk Profiling of Glaucoma: A Narrative Review

Importance

Glaucoma is the world's leading cause of irreversible blindness. Primary open-angle glaucoma (POAG) is typically asymptomatic early in the disease process, and unfortunately, many are diagnosed too late to prevent vision loss.

Observations

Genome-wide association studies, which evaluate the association between genetic variants and phenotype across the genome, have mapped many genes for POAG. As well as uncovering new biology, genetic information can be combined into a polygenic risk score (PRS), which aggregates an individual's disease risk over many genetic variants. In this nonsystematic review, performed from June 21, 2019, to October 1, 2020, we address a series of questions to explain the challenges and opportunities in translating genetic discoveries in POAG. We summarize what is known about POAG genetics and how its endophenotypes, such as intraocular pressure or cup-disc ratio, can help with prediction. We discuss the sample sizes available and how increases in the future may have an effect on the utility of prediction approaches. We explore particular scenarios, such as the use of PRS in risk stratification, and applications for individuals who are particularly high risk for POAG as a result of them carrying both a high penetrance mutation and an unfavorable PRS. Finally, we discuss the issue of equity in applying these tests and the prospects for prediction for people from various ancestry groups. The cost-effectiveness evaluation of glaucoma PRS in direct-to-consumer genetic testing and across different ancestry groups is warranted in future research.

Conclusions and Relevance

Advances in glaucoma genetics have opened the door for risk stratification based on genetic risk predictions. The PRS approach has shown good promise in predicting who will be at highest risk of POAG, which could improve outcomes if these predictions can be acted on to result in improved clinical outcomes.

Analysis of risk allele frequencies of single nucleotide polymorphisms related to open-angle glaucoma in different ethnic groups

BACKGROUND

The prevalence of open-angle glaucoma (OAG) varies from 0.5% to 7.0% among populations of diverse ancestry, suggesting the existence of genetic differences. The purposes of this study were to provide insights into genetic causes of OAG, which can result in prevalence and phenotype differences among populations of diverse ancestry for OAG, and to compare allele frequencies of intraocular pressure (IOP) elevation-related SNPs in OAG among Koreans and other ethnic groups.

METHODS

We collected the data on a total of 135 OAG-associated single nucleotide polymorphisms (SNPs) from a genome-wide association studies (GWAS) catalog. The population-level allele frequencies of these SNPs were derived based on the 1000 Genomes Project and Korean Reference Genome Database. We used Fisher's exact test to assess whether the effect allele at a given SNP was significantly enriched or depleted.

RESULTS

European, American, and South Asian populations showed similar heatmap patterns, while African, East Asian, and Korean populations had distinct patterns. Korean population presented different profiles compared to other groups; rs1579050 (FMNL2 gene), rs2024211 (CAV2;CAV1), and rs8141433 (GNB1L;TXNRD2 gene), which are known to be associated with IOP variation, were enriched in Americans, Europeans, and Africans, and depleted in Koreans. These can be the candidates for the causative genes of differences in the prevalence of IOP variation in OAG according to ethnic groups.

CONCLUSIONS

Differences in allele frequencies associated with IOP related SNPs between Koreans and other ethnicities were observed, which may explain the high prevalence of OAG with normal IOP predominantly in Koreans and East Asians.

Genetic background modifies vulnerability to glaucoma-related phenotypes in Lmx1b mutant mice

Variants in the LIM homeobox transcription factor 1-beta (LMX1B) gene predispose individuals to elevated intraocular pressure (IOP), a key risk factor for glaucoma. However, the effect of LMX1B mutations varies widely between individuals. To better understand the mechanisms underlying LMX1B-related phenotypes and individual differences, we backcrossed the Lmx1b^V265D (also known as Lmx1b^Icst ) allele onto the C57BL/6J (B6), 129/Sj (129), C3A/BLiA-Pde6b⁺ /J (C3H) and DBA/2J-Gpnmb⁺ (D2-G) mouse strain backgrounds. Strain background had a significant effect on the onset and severity of ocular phenotypes in Lmx1b^V265D/+ mutant mice. Mice of the B6 background were the most susceptible to developing abnormal IOP distribution, severe anterior segment developmental anomalies (including malformed eccentric pupils, iridocorneal strands and corneal abnormalities) and glaucomatous nerve damage. By contrast, Lmx1b^V265D mice of the 129 background were the most resistant to developing anterior segment abnormalities, had less severe IOP elevation than B6 mutants at young ages and showed no detectable nerve damage. To identify genetic modifiers of susceptibility to Lmx1b^V265D -induced glaucoma-associated phenotypes, we performed a mapping cross between mice of the B6 (susceptible) and 129 (resistant) backgrounds. We identified a modifier locus on Chromosome 18, with the 129 allele(s) substantially lessening severity of ocular phenotypes, as confirmed by congenic analysis. By demonstrating a clear effect of genetic background in modulating Lmx1b-induced phenotypes, providing a panel of strains with different phenotypic severities and identifying a modifier locus, this study lays a foundation for better understanding the roles of LMX1B in glaucoma with the goal of developing new treatments.

The Role of Genetic Ancestry as a Risk Factor for Primary Open-angle Glaucoma in African Americans

Purpose

POAG is the leading cause of irreversible blindness in African Americans. In this study, we quantitatively assess the association of autosomal ancestry with POAG risk in a large cohort of self-identified African Americans.

Methods

Subjects recruited to the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study were classified as glaucoma cases or controls by fellowship-trained glaucoma specialists. POAAGG subjects were genotyped using the MEGA Ex array (discovery cohort, n = 3830; replication cohort, n = 2135). Population structure was interrogated using principal component analysis in the context of the 1000 Genomes Project superpopulations.

Results

The majority of POAAGG samples lie on an axis between African and European superpopulations, with great variation in admixture. Cases had a significantly lower mean value of the ancestral component q0 than controls for both cohorts (P = 6.14-4; P = 3-6), consistent with higher degree of African ancestry. Among POAG cases, higher African ancestry was also associated with thinner central corneal thickness (P = 2-4). Admixture mapping showed that local genetic ancestry was not a significant risk factor for POAG. A polygenic risk score, comprised of 23 glaucoma-associated single nucleotide polymorphisms from the NHGRI-EBI genome-wide association study catalog, was significant in both cohorts (P < 0.001), suggesting that both known POAG single nucleotide polymorphisms and an omnigenic ancestry effect influence POAG risk.

Conclusions

In sum, the POAAGG study population is very admixed, with a higher degree of African ancestry associated with an increased POAG risk. Further analyses should consider social and environmental factors as possible confounding factors for disease predisposition.

Glaucoma as Neurodegeneration in the Brain

Glaucoma, a group of diseases characterized by progressive optic nerve degeneration that results in irreversible blindness, can be considered a neurodegenerative disorder of both the eye and the brain. Increasing evidence from human and animal studies have shown that glaucoma shares some common neurodegenerative pathways with Alzheimer’s disease (AD) and other tauopathies, such as chronic traumatic encephalopathy (CTE) and frontotemporal dementia. This hypothesis is based on the focal adhesion pathway hypothesis and the spreading hypothesis of tau. Not only has the Apolipoprotein E (APOE) gene been shown to be associated with AD, but also with primary open angle glaucoma (POAG). This review will highlight the relevant literature in the past 20 years from PubMed that show the pathogenic overlap between POAG and AD. Neurodegenerative pathways that contribute to transsynaptic neurodegeneration in AD and other tauopathies might also be similar to those in glaucomatous neurodegeneration.

Glaucoma in Adults-Screening, Diagnosis, and Management: A Review

IMPORTANCE

Glaucoma is the most common cause of irreversible blindness worldwide. Many patients with glaucoma are asymptomatic early in the disease course. Primary care clinicians should know which patients to refer to an eye care professional for a complete eye examination to check for signs of glaucoma and to determine what systemic conditions or medications can increase a patient's risk of glaucoma. Open-angle and narrow-angle forms of glaucoma are reviewed, including a description of the pathophysiology, risk factors, screening, disease monitoring, and treatment options.

OBSERVATIONS

Glaucoma is a chronic progressive optic neuropathy, characterized by damage to the optic nerve and retinal nerve fiber layer, that can lead to permanent loss of peripheral or central vision. Intraocular pressure is the only known modifiable risk factor. Other important risk factors include older age, nonwhite race, and a family history of glaucoma. Several systemic medical conditions and medications including corticosteroids, anticholinergics, certain antidepressants, and topiramate may predispose patients to glaucoma. There are 2 broad categories of glaucoma, open-angle and angle-closure glaucoma. Diagnostic testing to assess for glaucoma and to monitor for disease progression includes measurement of intraocular pressure, perimetry, and optical coherence tomography. Treatment of glaucoma involves lowering intraocular pressure. This can be achieved with various classes of glaucoma medications as well as laser and incisional surgical procedures.

CONCLUSIONS AND RELEVANCE

Vision loss from glaucoma can be minimized by recognizing systemic conditions and medications that increase a patient's risk of glaucoma and referring high-risk patients for a complete ophthalmologic examination. Clinicians should ensure that patients remain adherent with taking glaucoma medications and should monitor for adverse events from medical or surgical interventions used to treat glaucoma.

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.

Investigation of associations between Piezo1 mechanoreceptor gain-of-function variants and glaucoma-related phenotypes in humans and mice

Glaucoma disproportionately affects individuals of African descent. Prior studies of the PIEZO1 mechanoreceptor have suggested a possible role in glaucoma pathophysiology. Here, we investigated associations between a Piezo1 gain-of-function variant common in individuals of African descent with glaucoma-related phenotypes. We analyzed whole genome sequences to identify Piezo1 variants and their frequencies among 1565 human participants. For the most common variant (e756del), we compared phenotypes between heterozygotes, homozygotes, and wildtypes. Longitudinal mixed effects models of visual field mean deviation (MD) and retinal nerve fiber layer (RNFL) thickness were used to evaluate progression. Based on trends in the models, further investigation was conducted using Piezo1 gain-of-function mice. About 30% of African descent individuals had at least one e756del allele. There were trends suggesting e756del was associated with higher IOPs, thinner RNFLs, lower optic nerve head capillary densities, and greater decreases in MD and RNFL thickness over time, but these did not reach statistical significance. Among mice, increased Piezo1 activity was not significantly associated with IOP or retinal ganglion cell density. Our study confirms that the Piezo1 e756del gain-of-function variant is a frequent polymorphism present in African descent individuals but is unrelated to examined differences in glaucoma phenotypes. Ongoing work is needed to elucidate the role of Piezo1-mediated mechanotransduction in glaucoma.

Prevalence of primary open-angle glaucoma in a Somalia population

PURPOSE

To determine the prevalence of primary open-angle glaucoma (POAG) in patients over 40 years that presented to our tertiary hospital in Somalia Mogadishu.

METHODS

This prospective cross-sectional study included 1550 patients older than 40 years that presented to the ophthalmology clinic of Somalia Mogadishu - Turkey Training and Research Hospital. The patients were evaluated in terms of age, gender, intraocular pressure, and optical cup/disk (C/D) ratio, and central corneal thickness measurements were taken.

RESULTS

The prevalence of glaucoma in the study population over the age of 40 years was 7%. The prevalence of glaucoma was 40% in the 40-50-year group, 6.8% in the 50-60-year group, 7% in the 60-70-year group, 9.9% in the 70-80-year group, and 12.3% in the 80-90-year group. The prevalence of glaucoma statistically significantly increased with advancing age (p < 0.001). The mean intraocular pressure was measured as 16.7 ± 3.3 mmHg for the overall patient population, 16.3 ± 2.9 mmHg for the female patients, and 17.1 ± 3.1 mmHg for the male patients. The mean intraocular pressure of the patients diagnosed with POAG was 27.3 ± 4.2 mmHg, and their mean corneal thickness was 507.9 µm, which was significantly lower than the value of the patients without POAG (545.8) (p < 0.001). The mean C/D ratio was calculated as 0.56 ± 0.21 for the patients with POAG and general 0.24 ± 0.16 for the overall patient population, indicating a statistically significant difference (p < 0.001).

CONCLUSIONS

A high rate of POAG is seen in patients over 40 years of age in Somalia. The mechanism underlying POAG needs to be investigated in this population.

Use of the ICD-10 vision codes to study ocular conditions in Medicare beneficiaries with stroke

BACKGROUND

Ocular conditions are common following stroke and frequently occur in combination with pre-existing ophthalmologic disease. The Medicare International Statistical Classification of Diseases and Related Health Problems (ICD-10) coding system for identifying vision related health conditions provides a much higher level of detail for coding these complex scenarios than the previous ICD-9 system. While this new coding system has advantages for clinical care and billing, the degree to which providers and researchers are utilizing the expanded code structure is unknown. The purpose of this study was to describe the use of ICD-10 vision codes in a large cohort of stroke survivors.

METHODS

Retrospective cohort design to study national 100% Medicare claims files from 2015 through 2017. Descriptive data analyses were conducted using all available ICD-10 vision codes for beneficiaries who had an acute care stay because of a new stroke. The outcome of interest was ≥1 ICD-10 visual code recorded in the claims chart.

RESULTS

The cohort (n = 269,314) was mostly female (57.1%) with ischemic stroke (87.8%). Approximately 15% were coded as having one or more ocular condition. Unspecified glaucoma was the most frequently used code among men (2.83%), those over 85+ (4.80%) and black beneficiaries (4.12%). Multiple vision codes were used in few patients (0.6%). Less than 3% of those in the oldest group (85+ years) had two or more vision codes in their claims.

CONCLUSIONS

Ocular comorbidity was present in a portion of this cohort of stroke survivors, however the vision codes used to describe impairments in this population were few and lacked specificity. Future studies should compare ophthalmic examination results with billing codes to characterize the type and frequency of ocular comorbidity. It important to understand how the use of ICD-10 vision codes impacts clinical decision making, recovery, and outcomes.

Genetic Variants Associated With the Onset and Progression of Primary Open-Angle Glaucoma

PURPOSE

We sought to investigate the genetic variants associated with the onset and progression of primary open-angle glaucoma (POAG).

DESIGN

Case-control genetic association study.

METHODS

Japanese POAG patients (n = 505) and control subjects (n = 246) were genotyped for 22 genetic variants predisposing to POAG that can be classified into those associated with intraocular pressure (IOP) elevation (IOP-related genetic variants) and optic nerve vulnerability independent of IOP (non-IOP-related genetic variants). The total number of risk alleles of the 17 IOP-related and 5 non-IOP-related genetic variants were calculated as the genetic risk score (GRS), and the associations between the GRS and family history of glaucoma as an indicator of POAG onset and age at the diagnosis of glaucoma as an indicator of POAG progression were evaluated.

RESULTS

There was a significant association (P = .014; odds ratio 1.26 per GRS) between the non-IOP-related GRS, but not IOP-related GRS, and a family history of glaucoma in POAG. As the non-IOP-related GRS increased, the risk of a family history of glaucoma increased. In contrast, a significant association (P = .0014; β = -0.14) was found between the IOP-related GRS, but not non-IOP-related GRS, and age at the diagnosis of glaucoma. As the IOP-related GRS increased, age at the diagnosis of glaucoma decreased.

CONCLUSION

The results indicate that non-IOP-related (optic nerve vulnerability) rather than IOP-related (IOP elevation) genetic variants may play an important role in the onset of POAG (family history of glaucoma) and that IOP-related rather than non-IOP-related genetic variants may play an important role in its progression (age at the diagnosis of glaucoma).

Personalising surgical treatments for glaucoma patients

Surgical treatments for glaucoma have relied for decades on traditional filtering surgery such as trabeculectomy and, in more challenging cases, tubes. Antifibrotics were introduced to improve surgical success in patients at increased risk of failure but have been shown to be linked to a greater incidence of complications, some being potentially vision-threatening. As our understanding of glaucoma and its early diagnosis have improved, a more individualised management has been suggested. Recently the term "precision medicine" has emerged as a new concept of an individualised approach to disease management incorporating a wide range of individual data in the choice of therapeutic modalities. For glaucoma surgery, this involves evaluation of the right timing, individual risk factors, targeting the correct anatomical and functional outflow pathways and appropriate prevention of scarring. As a consequence, there is an obvious need for better knowledge of anatomical and functional pathways and for more individualised surgical approaches with new, less invasive and safer techniques allowing for earlier intervention. With the recent advent of minimally invasive glaucoma surgery (MIGS) a large number of novel devices have been introduced targeting potential new sites of the outflow pathway for lowering intraocular pressure (IOP). Their popularity is growing in view of the relative surgical simplicity and apparent lack of serious side effects. However, these new surgical techniques are still in an era of early experiences, short follow-up and lack of evidence of their superiority in safety and cost-effectiveness over the traditional methods. Each year several new devices are introduced while others are withdrawn from the market. Glaucoma continues to be the primary cause of irreversible blindness worldwide and access to safe and efficacious treatment is a serious problem, particularly in the emerging world where the burden of glaucoma-related blindness is important and concerning. Early diagnosis, individualised treatment and, very importantly, safe surgical management should be the hallmarks of glaucoma treatment. However, there is still need for a better understanding of the disease, its onset and progression, the functional and structural elements of the outflow pathways in relation to the new devices as well as their long-term IOP-lowering efficacy and safety. This review discusses current knowledge and the future need for personalised glaucoma surgery.

Short- and long-term outcomes of laparoscopic versus open gastrectomy for locally advanced gastric cancer following neoadjuvant chemotherapy

BACKGROUND

This study aimed to investigate the short- and long-term outcomes of laparoscopic gastrectomy (LG) in patients with advanced gastric cancer following neoadjuvant chemotherapy (NAC) to determine its safety and feasibility.

METHODS

We retrospectively investigated 51 patients who underwent gastrectomy for locally advanced gastric cancer [cT3-4/N1-3 or macroscopic type 3 (> 80 mm) or type 4] following NAC between November 2009 and January 2018. After excluding two patients who underwent palliative surgery due to peritoneal dissemination, 49 patients were ultimately selected for this cohort study. The patients were then divided into the LG group and open gastrectomy (OG) group, after which the clinicopathological characteristics as well as short- and long-term outcomes were examined.

RESULTS

Compared with the OG group, the LG group demonstrated a significantly lower amount of intraoperative blood loss and a shorter hospital stay. The overall complication rates were 10% (2 of 20 patients) and 24% (7 of 29 patients) in the LG and OG groups (P = 0.277), respectively. No significant differences in 5-year disease-free (LG 44.4% vs. OG 53.3%; P = 0.382) or overall survival rates (LG 46.9% vs. OG 54.0%; P = 0.422) were observed between the groups. Multivariate analysis revealed that the surgical procedure (LG vs. OG) was not an independent risk factor for disease-free (P = 0.645) or overall survival (P = 0.489).

CONCLUSIONS

LG may be a potential therapeutic option for patients with gastric cancer following NAC considering its high success rates and acceptable short- and long-term outcomes.