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

Missed Opportunities in Screening for Glaucoma

PURPOSE

To create a holistic and realistic view regarding current knowledge, understanding, and challenges of screening in general and in glaucoma.

METHODS/RESULTS

Based upon available literature, all systems suffer from the same challenges: huge variability of care practices (despite guidelines), simultaneous under care and over care, as well as the unsustainable increase of costs. While the magnitude of these challenges differs immoderately between well-off and developing countries, the Western world has already demonstrated that simply doing more than what we currently do is not the solution. System outcomes also matter in screening, that is, its benefits should outweigh any harms (over-care, false positives/negatives, uncertain findings, etc.) and be cost-effective. However, even when the evidence does not support screening (as is currently the case in glaucoma), it may feel justified as "at least we are doing something." Strong commercial interests, lobbying and politics star as well and will influence the control arm even in high-quality randomized screening trials (RCT).

CONCLUSIONS

As resources will never be sufficient for all health care activities that providers wish to deliver and what people wish to receive, we need to ask big questions and adopt a public health perspective in glaucoma and eye care. How can we create and maintain a sustainable balance between finding and treating underserved high-risk patients without burdening the broader patient population and societies with over-diagnostics and treatments? Considering numerous biases related to screening, including the variability in care practices, a high-quality RCT for the screening of glaucoma would be very challenging to organize and evaluate its universal usefulness.

Screening Strategies and Methodologies

PRCIS

While glaucoma is a leading cause of irreversible vision loss, it presents technical challenges in the design and implementation of screening. New technologies such as PRS and AI offer potential improvements in our ability to identify people at high risk of sight loss from glaucoma and may improve the viability of screening for this important disease.

PURPOSE

To review the current evidence and concepts around screening for glaucoma.

METHODS/RESULTS

A group of glaucoma-focused clinician scientists drew on knowledge and experience around glaucoma, its etiology, and the options for screening. Glaucoma is a chronic progressive optic neuropathy affecting around 76 million individuals worldwide and is the leading cause of irreversible blindness globally. Early stages of the disease are asymptomatic meaning a substantial proportion of cases remain undiagnosed. Early detection and timely intervention reduce the risk of glaucoma-related visual morbidity. However, imperfect tests and a relatively low prevalence currently limit the viability of population-based screening approaches. The diagnostic yield of opportunistic screening strategies, relying on the identification of disease during unrelated health care encounters, such as cataract clinics and diabetic retinopathy screening programs, focusing on older people and/or those with a family history, are hindered by a large number of false-positive and false-negative results. Polygenic risk scores (PRS) offer personalized risk assessment for adult-onset glaucoma. In addition, artificial intelligence (AI) algorithms have shown impressive performance, comparable to expert humans, in discriminating between potentially glaucomatous and non-glaucomatous eyes. These emerging technologies may offer a meaningful improvement in diagnostic yield in glaucoma screening.

CONCLUSIONS

While glaucoma is a leading cause of irreversible vision loss, it presents technical challenges in the design and implementation of screening. New technologies such as PRS and AI offer potential improvements in our ability to identify people at high risk of sight loss from glaucoma and may improve the viability of screening for this important disease.

Screening of Glaucoma: Consensus and Directions

PURPOSE

Glaucoma is a leading public health concern globally. This summary discusses barriers to glaucoma screening and novel strategies for a cost-effective glaucoma screening.

METHODS/RESULTS

We discuss barriers to glaucoma screening and recent advancements in glaucoma detection and care, including targeted screening approach as well as telemedicine, genetic testing, and artificial intelligence (AI). A major barrier to glaucoma screening is the cost-effectiveness of case finding resulting from the low prevalence of the disease and the complexity of the diagnosis. Targeted-screening, as well as multi-level screening, can reduce the false positive rate and increase the cost-effectiveness of the program. Telemedicine, availability of genetic testing and polygenic risk scores, and AI provide the opportunity for novel glaucoma screening programs in primary care, portable, and home-based settings and will be helpful for lowering the costs, identifying patients in need of urgent treatment and enabling timely diagnosis and early intervention.

CONCLUSIONS

Screening of glaucoma is challenging and changing. Recent advancements in digital technology and genetics have led to the development of tools that are promising for novel screening methodologies. Clinical trials are needed to demonstrate the long-term effect of targeted screening on the burden of glaucoma worldwide.

The Significance of Screening Family Members in Glaucoma: Opportunities and Challenges

PRECIS

This article delves into the imperative of screening family members of patients with glaucoma due to the disease's hereditary nature. It discusses the significant risks faced by first-degree relatives, approaches for identification, and challenges in implementing effective screening strategies. Emphasizing education, targeted campaigns, community involvement, and collaborative healthcare approaches, the article highlights the potential for mitigating undiagnosed glaucoma cases through strategic interventions targeting high-risk individuals.

PURPOSE

This article underscores the importance of screening family members of glaucoma patients, emphasizing the hereditary nature of the disease and the potential for screening to allow for early intervention to help prevent unnecessary vision loss.

METHODS/RESULTS

Glaucoma, affecting over 111.8 million by 2040, is relatively asymptomatic until late in the disease. Genetics predispose to glaucoma, with up to 70% heritability. High-risk individuals, particularly first-degree relatives, exhibit substantially elevated glaucoma risks-up to 22% compared with 2.3% in controls. Family history also correlates with greater disease severity. Identifying high-risk family members through cascade screenings for causative genes or direct examinations during proband visits emerges as efficient strategies. Challenges persist, including slow progression, healthcare accessibility, and ethical dilemmas in implementing family member screening. Challenges extend to the healthcare system, socioeconomic barriers, and familial communication issues. Efforts to educate probands and the public on the hereditary nature of glaucoma are pivotal. Tailored education campaigns, leveraging clinic visits, and community screenings, complemented by optometrist collaboration, form essential strategies.

CONCLUSIONS

Although challenges hinder family member screening, educating probands, targeted patient education, collaborative healthcare approaches, and community involvement offer promising avenues to combat undiagnosed glaucoma cases.

Glaucoma Screening Guidelines Worldwide

PRCIS

Recommendations for glaucoma screening vary significantly from organization to organization, and while worldwide screening is currently not recommended, there is support in many organizations for screening at-risk subgroups of the general population.

OBJECTIVE

To summarize and compare current glaucoma screening protocols of major national and international, governmental, and non-governmental organizations.

METHODS

A general review of the major medical, and more specifically ophthalmic, organizations within North America, South America, Europe, Asia, and Africa was undertaken. Protocols from recent international and regional meetings were reviewed and summarized and a comparative analysis was employed to highlight differences between national and regional policies.

RESULTS

In general, it was found that worldwide screening for glaucoma is currently of limited clinical utility and unlikely to be cost-effective. However, a more targeted approach is recommended by some major organizations, including the American Academy of Ophthalmology, the Pan-American Association of Ophthalmology, and the International Council of Ophthalmology in conjunction with a group of prominent ophthalmologists based in Sub-Saharan Africa recommend a targeted approach to screening specific populations that are deemed to be at higher risk of developing glaucoma.

CONCLUSION

General population screening for glaucoma has been adopted as a recommendation by only a few organizations and only in specific situations. It is the screening of high-risk populations that has been demonstrated to be not only clinically useful in diagnosing and treating larger proportions of the general population benefiting from a higher positive-predictive value for screening protocols in these groups but also cost-effective. Further research is needed to create cost-effective protocols to successfully screen these high-risk populations for glaucoma using methods that are sufficiently sensitive and specific.

Predicting perimetric defects from en face maps of retinal nerve fibre layer reflectance

PURPOSE

To develop criteria to predict visual hemifields with deep perimetric defects based on retinal nerve fibre layer (RNFL) reflectance, in a transparent process whose components can be assessed by independent laboratories analysing data from their own small groups.

METHODS

The analysis was carried out in four stages, using three independent groups of patients-30, 33 and 62 participants-with glaucoma and age-similar controls. The first stage used Group 1 to develop a criterion for RNFL reflectance images at 24, 36 or 48 μm below the inner limiting membrane (ILM). The second stage evaluated the criterion using Group 2. The third stage developed a second criterion to improve performance for Groups 1 and 2 combined. The fourth stage evaluated the second criterion with Group 3. Confidence intervals for sensitivity and specificity were then computed by combining results from all three groups.

RESULTS

The first criterion identified all hemifields with deep defects and no hemifields from controls, using a within-eye reference for healthy RNFL. For Group 2, specificity remained high but sensitivity was reduced. The second criterion improved sensitivity by using location-specific reference values. For Group 3, sensitivity remained high but reduced specificity was found. Confidence intervals showed substantial overlap for the two criteria.

CONCLUSIONS

We developed two criteria to identify patients with deep perimetric defects with high specificity and sensitivity. Several improvements are warranted: automated identification of the fovea-disc angle and optic disc locations, evaluation of normal variation in patterns of RNFL thickness, improved segmentation of ILM and major vasculature, reduction of within-eye variability in RNFL reflectance of healthy eyes, assessment of effects of image quality, assessment of effects of comorbidity and effectiveness of other devices.

[Bibliometric study and analysis of citation networks of visual screening in primary care]

AIM

Screenings make it possible to detect anomalies that can be treated and identify patients who require referral to a specialist. The objective is to identify the different areas of research and determine the most cited publications on screening in primary care.

METHODS

An analysis of publications and visualization of citation networks has been carried out using the Citation Network Explorer software. The bibliographic search was carried out with the Web of Science (WOS) database using the search term: "screening AND (vision OR eye OR ocular OR visual)".

RESULTS

We analyzed 16707 publications in all fields, 23919 citation networks have been found. The number of publications has increased, with 2021 being the year with the highest number. The majority are scientific articles and the predominant language is English. The most cited article is a global meta-analysis on the prevalence of glaucoma, showing the importance of screening for its early detection since it is essential to avoid blindness. Using the clustering function we found 8 groups with a significant number of publications where we have bibliography on certain eye diseases: glaucoma, diabetic retinopathy, pediatric amblyopia, keratoconus and dry eye.

CONCLUSIONS

The main areas of study in relation to screening are the detection of diseases such as glaucoma, retinopathy of prematurity, keratoconus and dry eye. As well as the detection through visual analysis of childhood amblyopia and vision loss in elderly patients. It also gives importance to performing ocular motility tests in problems of acquired brain damage.

Lessons From The Glaucoma Foundation Think Tank 2023: A Patient-Centric Approach to Glaucoma

PRCIS

The main takeaways also included that BIG DATA repositories and AI are important combinatory tools to foster novel strategies to prevent and stabilize glaucoma and, in the future, recover vision loss from the disease.

PURPOSE

To summarize the main topics discussed during the 28th Annual Glaucoma Foundation Think Tank Meeting "A Patient-Centric Approach to Glaucoma" held in New York on June 9 and 10, 2023.

METHODS

The highlights of the sessions on BIG DATA, genetics, modifiable lifestyle risk factors, female sex hormones, and neuroprotection in the field of primary open angle glaucoma (POAG) were summarized.

RESULTS

The researchers discussed the importance of BIG DATA repositories available at national and international levels for POAG research, including the United Kingdom Biobank. Combining genotyped large cohorts worldwide, facilitated by artificial intelligence (AI) and machine-learning approaches, led to the milestone discovery of 312 genome-wide significant disease loci for POAG. While these loci could be combined into a polygenic risk score with clinical utility, Think Tank meeting participants also provided analytical epidemiological evidence that behavioral risk factors modify POAG polygenetic risk, citing specific examples related to caffeine and alcohol use. The impact of female sex hormones on POAG pathophysiology was discussed, as was neuroprotection and the potential use of AI to help mitigate specific challenges faced in clinical trials and speed approval of neuroprotective agents.

CONCLUSIONS

The experts agreed on the importance of genetics in defining individual POAG risk and highlighted the additional crucial role of lifestyle, gender, blood pressure, and vascular risk factors. The main takeaways also included that BIG DATA repositories and AI are important combinatory tools to foster novel strategies to prevent and stabilize glaucoma and, in the future, recover vision loss from the 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.

Measures of multiple deprivation and visual field loss in glaucoma clinics in England: lessons from big data

BACKGROUND/OBJECTIVES

To examine the association between multiple deprivation with late diagnosis and rapid worsening of glaucoma in patients in English hospital eye services (HES).

METHODS

602,439 visual fields (VFs) were extracted from five regionally different glaucoma clinics in England. Mean Deviation (MD) worse than -12 dB was used as a surrogate definition for advanced VF loss at diagnosis in patients with ≥2 reliable VF records. MD loss worse than -1 dB per year was used to define rapid VF progression in patients with ≥6 VFs. Patient data were stratified into deciles of the Index of Multiple Deprivation (IMD) from residential postcodes.

RESULTS

There was an association between IMD and advanced VF loss at diagnosis in 44,956 patients with 18% (293/1608) and 11% (771/6929) in the most and least deprived IMD decile, respectively. Age-corrected odds ratio (OR) for having advanced VF loss at entry into HES was 1.42 (95% confidence interval [CI] 1.21-1.67) and 0.75 (95% CI: 0.66-0.85) in the most and least deprived IMD decile respectively (reference = fifth decile). In 15,094 patients with follow up data (median [interquartile range] of 6.9 [4.5, 10.0] years), the proportion having rapid VF progression did not differ across the IMD spectrum.

CONCLUSION

Large-scale VF data from clinics indicates that glaucoma severity at presentation to English HES is associated with levels of multiple deprivation. We found no evidence to suggest likelihood of having rapid VF progression during follow-up is associated with IMD; this hints at equity of glaucoma care and outcomes once patients are in English HES.

[Awareness for glaucoma in the general population]

BACKGROUND

Glaucoma is not a rare entity but because very few symptoms occur and visual field defects are frequently first recognized at a late stage, a large proportion of glaucoma diseases remain undetected. The aim of this study was to identify the proportion of undiagnosed glaucoma in German population-based cohort studies and to contextualize them in the context of the literature.

MATERIAL AND METHODS

The prevalence of glaucoma in the Gutenberg Health Study (GHS) and the age-related investigations on health of the University of Regensburg (AugUR) was evaluated based on visual field examinations and optic disc color photography according to the ISGEO criteria. Furthermore, the self-reported glaucoma diagnoses were collected and the proportion of undiagnosed glaucoma was determined.

RESULTS

The proportion of undiagnosed glaucoma was 55% in the GHS, and 53% in the AugUR study. The results correlate with results from previous studies from other countries in which the proportion of unrecognized glaucoma ranged from 33% to 78%. In the GHS and the AugUR study the proportion of undiagnosed glaucoma was higher in younger age groups and in women.

DISCUSSION

Roughly every second case of glaucoma is undetected. As the symptoms are often nonspecific or take a long time to appear, there is a risk of advanced glaucomatous visual field defects or blindness due to a lack of glaucoma awareness. Studies have shown that a systematic screening can halve this risk.

Potential for Collider Bias in Studies Examining the Association of Central Corneal Thickness With Glaucoma

Purpose

Central corneal thickness (CCT) may be biologically related to glaucoma or observed as associated with glaucoma simply due to its effect on intraocular pressure (IOP) measurement. We aimed to determine if the previously reported CCT-glaucoma associations, in which the analyses were adjusted for IOP or participants were selected on IOP, could be explained by collider bias.

Methods

We simulated datasets mimicking a longitudinal population-based study (Los Angeles Latino Eye Study) and a trial (Ocular Hypertension Treatment Study) such that: (i) CCT was not truly associated with glaucoma, (ii) CCT and true IOP both contribute to measured IOP, and (iii) true IOP contributes to glaucoma risk. We then tested whether an association between CCT and glaucoma could be spuriously induced simply by adjusting for or selecting on measured IOP.

Results

A thinner CCT was significantly associated with higher glaucoma incidence in the simulated longitudinal population-based study when adjusted for measured IOP, but not crudely (unadjusted). A thinner CCT was crudely associated with glaucoma incidence in the simulated trial in which the participants were selected for high measured IOP. Effect sizes in the simulations were similar to those observed in the original studies.

Conclusions

Our findings question whether CCT is biologically associated with glaucoma and suggest that current evidence may be due to collider bias. This indicates that CCT alone cannot be used as a factor to identify people at high risk of glaucoma in the general population. Using CCT in combination with IOP may be superior to using IOP alone.

Association Between Myopic Refractive Error and Primary Open-Angle Glaucoma: A 2-Sample Mendelian Randomization Study

Importance

Refractive error (RE) is the most common form of visual impairment, and myopic RE is associated with an increased risk of primary open-angle glaucoma (POAG). Whether this association represents a causal role of RE in the etiology of POAG remains unknown.

Objective

To evaluate shared genetic influences and investigate the association of myopic RE with the risk for POAG.

Design, Setting, and Participants

Observational analyses were used to evaluate the association between mean spherical equivalent (MSE) RE (continuous trait) or myopia (binary trait) and POAG risk in individuals from the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort. To quantify genetic overlap, genome-wide genetic correlation analyses were performed using genome-wide association studies (GWAS) of MSE RE or myopia and POAG from GERA. Potential causal effects were assessed between MSE RE and POAG using 2-sample Mendelian randomization. Genetic variants associated with MSE RE were derived using GWAS summary statistics from a GWAS of RE conducted in 102 117 UK Biobank participants. For POAG, we used GWAS summary statistics from our previous GWAS (3836 POAG cases and 48 065 controls from GERA). Data analyses occurred between July 2020 and October 2021.

Main Outcomes and Measure

Our main outcome was POAG risk as odds ratio (OR) caused by per-unit difference in MSE RE (in diopters).

Results

Our observational analyses included data for 54 755 non-Hispanic White individuals (31 926 [58%] females and 22 829 [42%] males). Among 4047 individuals with POAG, mean (SD) age was 73.64 (9.20) years; mean (SD) age of the 50 708 controls was 65.38 (12.24) years. Individuals with POAG had a lower refractive MSE and were more likely to have myopia or high myopia compared with the control participants (40.2% vs 34.1%, P = 1.31 × 10-11 for myopia; 8.5% vs 6.8%, P = .004 for high myopia). Our genetic correlation analyses demonstrated that POAG was genetically correlated with MSE RE (rg, -0.24; SE, 0.06; P = 3.90 × 10-5), myopia (rg, 0.21; SE, 0.07; P = .004), and high myopia (rg, 0.23; SE, 0.09; P = .01). Genetically assessed refractive MSE was negatively associated with POAG risk (inverse-variance weighted model: OR per diopter more hyperopic MSE = 0.94; 95% CI, 0.89-0.99; P = .01).

Conclusions and Relevance

These findings demonstrate a shared genetic basis and an association between myopic RE and POAG risk. This may support population POAG risk stratification and screening strategies, based on RE information.

Terrestrial health applications of visual assessment technology and machine learning in spaceflight associated neuro-ocular syndrome

The neuro-ocular effects of long-duration spaceflight have been termed Spaceflight Associated Neuro-Ocular Syndrome (SANS) and are a potential challenge for future, human space exploration. The underlying pathogenesis of SANS remains ill-defined, but several emerging translational applications of terrestrial head-mounted, visual assessment technology and machine learning frameworks are being studied for potential use in SANS. To develop such technology requires close consideration of the spaceflight environment which is limited in medical resources and imaging modalities. This austere environment necessitates the utilization of low mass, low footprint technology to build a visual assessment system that is comprehensive, accessible, and efficient. In this paper, we discuss the unique considerations for developing this technology for SANS and translational applications on Earth. Several key limitations observed in the austere spaceflight environment share similarities to barriers to care for underserved areas on Earth. We discuss common terrestrial ophthalmic diseases and how machine learning and visual assessment technology for SANS can help increase screening for early intervention. The foundational developments with this novel system may help protect the visual health of both astronauts and individuals on Earth.

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.