Progression detection in glaucoma can be made more efficient by using a variable interval between successive visual field tests

Effect of Testing Frequency on the Time to Detect Glaucoma Progression With Optical Coherence Tomography (OCT) and OCT Angiography

PURPOSE

To determine how the frequency of testing affects the time required to detect statistically significant glaucoma progression for circumpapillary retinal nerve fiber layer (cpRNFL) with optical coherence tomography (OCT) and circumpapillary capillary density (cpCD) with OCT angiography (OCTA).

DESIGN

Retrospective, observational cohort study.

METHODS

In this longitudinal study, 156 eyes of 98 patients with glaucoma followed up over an average of 3.5 years were enrolled. Participants with 4 or more OCT and OCTA tests were included to measure the longitudinal rates of cpRNFL thickness and cpCD change over time using linear regression. Estimates of variability were then used to re-create real-world cpRNFL and cpCD data by computer simulation to evaluate the time required to detect progression for various loss rates and different testing frequencies.

RESULTS

The time required to detect a statistically significant negative cpRNFL and cpCD slope decreased as the testing frequency increased, albeit not proportionally. cpCD detected progression slightly earlier than cpRNFL. Eighty percent of eyes with a cpCD loss of -1%/y were detected after 6.0, 4.2, and 4 years when testing was performed 1, 2, and 3 times per year, respectively. Progression in 80% of eyes with a cpRNFL loss of -1 µm/y was detected after 6.3, 5.0, and 4.2 years, respectively.

CONCLUSIONS

cpRNFL and cpCD are comparable in detecting progression. As there were only small changes in the time to detect progression when testing increased from 2 to 3 times per year, testing twice per year may provide sufficient information for detecting progression with either OCT or OCTA in clinical settings.

Patient and Provider Perspectives on Glaucoma Treatment Adherence: A Delphi Study in Urban Alabama

SIGNIFICANCE

Patients with glaucoma and providers recognized perceived treatment efficacy, patient-provider relationship, psychological stress, instillation skill, good quality of life, and forgetfulness as key determinants of glaucoma adherence. This shared insight could help shape the development of clinical and behavioral interventions for addressing treatment barriers and improving adherence.

PURPOSE

Despite their impact on adherence in glaucoma, sociobehavioral factors may not be adequately explored during clinical consultations. We aimed to elicit consensus between patients and providers around key determinants of adherence and hypothesized that patients would place greater emphasis on sociobehavioral factors compared with providers.

METHODS

A two-round Delphi survey was used to assess treatment beliefs, barriers, facilitators, motivators, and needs among 18 patients with glaucoma and providers. In round 1, agreement with 46 statements was scored on a 5-point Likert scale (strongly disagree to strongly agree). Statements with which 80% or more of panelists agreed reached consensus and advanced to round 2, where participants were asked to prioritize them based on their importance to treatment.

RESULTS

There was consensus regarding the influence of perceived treatment efficacy, good provider relationship, good quality of life, psychological stress, glaucoma knowledge, instillation skill, and forgetfulness on glaucoma adherence. For statements that failed to reach consensus, the Bonferroni-corrected Mann-Whitney U test revealed that the greatest differences between patients and providers pertained to regimen complexity (provider median, 4 [interquartile range {IQR}, 1]; patient median, 1.5 [IQR, 1]; P = .002), instillation skill (providers, 4 [IQR, 0.5]; patients, 2 [IQR, 1]; P = .001), and low motivation (providers, 3 [IQR, 2.25]; patients, 1 [IQR, 0]; P = .003).

CONCLUSIONS

Although patients and providers prioritized sociobehavioral factors as key determinants of adherence, disagreement between these groups was observed in other areas. Continued juxtaposition of patient and provider perspectives could spotlight underexplored areas and guide the development of successful interventions for improving adherence.

Functional assessment of glaucoma: Uncovering progression

Clinicians who manage glaucoma patients carefully monitor the visual field to determine if treatments are effective or interventions are needed. Visual field tests may reflect disease progression or variability among examinations. We describe the approaches and perimetric tests used to evaluate glaucomatous visual field progression and factors that are important for identifying progression. These include stimulus size, which area of the visual field to assess (central versus peripheral), and the testing frequency, evaluating which is important to detect change early while minimizing patient testing burden. We also review the different statistical methods developed to identify change. These include trend- and event-based analyses, parametric and nonparametric tests, population-based versus individualized approaches, as well as pointwise and global analyses. We hope this information will prove useful and important to enhance the management of glaucoma patients. Overall, analysis procedures based on series of at least 5 to 6 examinations that require confirmation and persistence of changes, that are guided by the pattern and shape of the glaucomatous visual field deficits, and that are consistent with structural defects provide the best clinical performance.

Frequency of Testing to Detect Visual Field Progression Derived Using a Longitudinal Cohort of Glaucoma Patients

PURPOSE

To determine the time required to detect statistically significant progression for different rates of visual field loss using standard automated perimetry (SAP) when considering different frequencies of testing using a follow-up scheme that resembles clinical practice.

DESIGN

Observational cohort study.

PARTICIPANTS

One thousand seventy-two eyes of 665 patients with glaucoma followed up over an average of 4.3±0.9 years.

METHODS

Participants with 5 or more visual field tests over a 2- to 5-year period were included to derive the longitudinal measurement variability of SAP mean deviation (MD) using linear regressions. Estimates of variability then were used to reconstruct real-world visual field data by computer simulation to evaluate the time required to detect progression for various rates of visual field loss and different frequencies of testing. The evaluation was performed using a follow-up scheme that resembled clinical practice by requiring a set of 2 baseline tests and a confirmatory test to identify progression.

MAIN OUTCOME MEASURES

Time (in years) required to detect progression.

RESULTS

The time required to detect a statistically significant negative MD slope decreased as the frequency of testing increased, albeit not proportionally. For example, 80% of eyes with an MD loss of -2 dB/year would be detected after 3.3, 2.4, and 2.1 years when testing is performed once, twice, and thrice per year, respectively. For eyes with an MD loss of -0.5 dB/year, progression can be detected with 80% power after 7.3, 5.7, and 5.0 years, respectively.

CONCLUSIONS

This study provides information on the time required to detect progression using MD trend analysis in glaucoma eyes when different testing frequencies are used. The smaller gains in the time to detect progression when testing is increased from twice to thrice per year suggests that obtaining 2 reliable tests at baseline followed by semiannual testing and confirmation of progression through repeat testing in the initial years of follow-up may provide a good compromise for detecting progression, while minimizing the burden on health care resources in clinical practice.

More frequent, more costly? Health economic modelling aspects of monitoring glaucoma patients in England

BACKGROUND

Chronic open angle glaucoma (COAG) is an age-related eye disease causing irreversible loss of visual field (VF). Health service delivery for COAG is challenging given the large number of diagnosed patients requiring lifelong periodic monitoring by hospital eye services. Yet frequent examination better determines disease worsening and speed of VF loss under treatment. We examine the cost-effectiveness of increasing frequency of VF examinations during follow-up using a health economic model.

METHODS

Two different VF monitoring schemes defined as current practice (annual VF testing) and proposed practice (three VF tests per year in the first 2 years after diagnosis) were examined. A purpose written health economic Markov model is used to test the hypothesis that cost effectiveness improves by implementing proposed practice on groups of patients stratified by age and severity of COAG. Further, a new component of the model, estimating costs of visual impairment, was added. Results were derived from a simulated cohort of 10000 patients with quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) used as main outcome measures.

RESULTS

An ICER of £21,392 per QALY was derived for proposed practice improving to a value of £11,382 once savings for prevented visual impairment was added to the model. Proposed practice was more cost-effective in younger patients. Proposed practice for patients with advanced disease at diagnosis generated ICERs > £60,000 per QALY; these cases would likely be on the most intensive treatment pathway making clinical information on speed of VF loss redundant. Sensitivity analysis indicated results to be robust in relation to hypothetical willingness to pay threshold identified by national guidelines, although greatest uncertainty was allied to estimates of implementation and visual impairment costs.

CONCLUSION

Increasing VF monitoring at the earliest stages of follow-up for COAG appears to be cost-effective depending on reasonable assumptions about implementation costs. Our health economic model highlights benefits of stratifying patients to more or less monitoring based on age and stage of disease at diagnosis; a prospective study is needed to prove these findings. Further, this works highlights gaps in knowledge about long term costs of visual impairment.

Incorporating Spatial Models in Visual Field Test Procedures

Purpose

To introduce a perimetric algorithm (Spatially Weighted Likelihoods in Zippy Estimation by Sequential Testing [ZEST] [SWeLZ]) that uses spatial information on every presentation to alter visual field (VF) estimates, to reduce test times without affecting output precision and accuracy.

Methods

SWeLZ is a maximum likelihood Bayesian procedure, which updates probability mass functions at VF locations using a spatial model. Spatial models were created from empirical data, computational models, nearest neighbor, random relationships, and interconnecting all locations. SWeLZ was compared to an implementation of the ZEST algorithm for perimetry using computer simulations on 163 glaucomatous and 233 normal VFs (Humphrey Field Analyzer 24-2). Output measures included number of presentations and visual sensitivity estimates.

Results

There was no significant difference in accuracy or precision of SWeLZ for the different spatial models relative to ZEST, either when collated across whole fields or when split by input sensitivity. Inspection of VF maps showed that SWeLZ was able to detect localized VF loss. SWeLZ was faster than ZEST for normal VFs: median number of presentations reduced by 20% to 38%. The number of presentations was equivalent for SWeLZ and ZEST when simulated on glaucomatous VFs.

Conclusions

SWeLZ has the potential to reduce VF test times in people with normal VFs, without detriment to output precision and accuracy in glaucomatous VFs.

Translational Relevance

SWeLZ is a novel perimetric algorithm. Simulations show that SWeLZ can reduce the number of test presentations for people with normal VFs. Since many patients have normal fields, this has the potential for significant time savings in clinical settings.

Are rates of vision loss in patients in English glaucoma clinics slowing down over time? Trends from a decade of data

PURPOSE

To examine changes in rates of visual field (VF) progression in patients attending a sample of glaucoma clinics in England between 1999 and 2012.

METHODS

An archive of 473 252 Humphrey VFs recorded across the UK was retrospectively examined. Distribution of rates recorded in the first half of the decade was compared with the second. The relationship between age and severity of MD loss at baseline with rates of loss and frequency of testing was examined.

RESULTS

VF series from 18 926 eyes were analysed. Median rate of MD loss for the period before and after 2003 was -0.11 and -0.06 dB/year, respectively, but the proportion of eyes with medium or fast rates of MD loss remained constant. Median rate of MD loss in older (>70 years) eyes was faster than that observed in younger (<60 years) eyes (-0.21 compared with -0.01 dB/year). Median rate of loss did not vary with severity of MD loss at baseline. Frequency of testing, typically carried out annually, did not vary by age, rate of loss or disease severity.

CONCLUSIONS

VFs of eyes treated in the first half of the decade deteriorated more rapidly than those in the second half. Several factors might explain these differences but average effects were small and there was no reduction in the proportion of rapidly progressing eyes over the decade. Older age and, to a lesser extent, worse VF damage at diagnosis are indicators for faster VF loss in clinics, but frequency of VF testing was similar for all patients.

Frequency of visual field testing when monitoring patients newly diagnosed with glaucoma: mixed methods and modelling

Background

Visual field (VF) tests are the benchmark for detecting and monitoring the eye disease glaucoma. Measurements from VF tests are variable, which means that frequent monitoring, perhaps over a long period of time, is required to accurately detect true glaucomatous progression. In 2009, guidelines for the diagnosis and management of glaucoma issued by the National Institute for Health and Care Excellence revealed an absence of research evidence about the clinical effectiveness and cost-effectiveness of using different monitoring intervals to detect disease progression. However, the European Glaucoma Society (EGS) guidelines on patient examination recommend that newly diagnosed glaucoma patients should undergo VF testing three times per year in the first 2 years after initial diagnosis.

Objectives

The primary objective of this project was to explore the clinical effectiveness and cost-effectiveness of using different monitoring intervals to detect VF progression in newly diagnosed glaucoma patients. Other objectives sought to (1) explore glaucoma patients’ views and experiences of monitoring using focus groups; and (2) establish glaucoma subspecialists’ attitudes regarding frequency of VF testing using a five-item questionnaire.

Design

These questions were investigated using a multicentre audit of current practice and existing NHS data (VF records from almost 90,000 patients). New research knowledge was provided through statistical and health economic modelling of these and additional published data.

Results

The multicentre audit showed that VF monitoring is, on average, carried out annually. Patient focus groups indicated that, although patients do not like VF testing, they accept it as a critical part of their care. Patients raised concerns regarding distracting testing environments, quality of instructions, explanation of results and excessive waiting times. Questionnaires revealed that clinicians’ attitudes towards the frequency of VF testing varied considerably, and many glaucoma specialists believed that current recommendations are impractical. Statistical modelling suggested that EGS recommendations could be clinically effective as progression can be identified sooner than is possible with annual testing. Health economic modelling suggested that increased VF monitoring may also be cost-effective [incremental cost-effectiveness ratio (ICER) was equal to £21,679].

Conclusions

Statistical modelling of VF data suggests there is strong rationale for following EGS recommendations with the primary benefit of providing better information about fast-progressing patients. Our health economic model suggested that increasing VF testingmaybe cost-effective (ICER was equal to £21,679), especially when accounting for gains to society. Nevertheless, many clinicians consider increased VF testing of patients impossible with current resources. In addition, patient focus groups raised concerns about the practicalities of delivery of VF tests.

Future work

Results from this study could inform the design of a prospective randomised comparative trial of different VF monitoring intervals in glaucoma linked to stratifying patients according to risk factors for progression. The statistical model for VF data can be further developed to be used as a practical tool for optimising individualised follow-up. The views of clinicians and patients indicate that service delivery of VF testing is an important issue and worthy of further investigation. Ensuring the confidence and co-operation of the patient should be at the centre of future research into the most efficient strategies for glaucoma monitoring.

Funding

This work was funded by the National Institute for Health Research Health Services and Delivery Research programme.

Current status of visual field examination in Andalusia, Spain: the SICVA Study

PURPOSE

To ascertain the frequency of visual field examination (VFE) in patients attending public Andalusian hospitals (the SICVA study).

METHODS

This was a multicenter, observational, retrospective study of patients with documented and/or suspected glaucoma subject to campimetric monitoring for longer than 2 years. The numbers of VFEs performed in the first 2 years and in the complete follow-up period were analyzed. Data on VFE reliability were studied and VFE change was collected based on the Glaucoma Staging System 2.

RESULTS

A total of 722 eyes (from 467 consecutive patients), 349 with suspected and 373 with documented glaucoma, were included. Mean patient age was 65.9 years (SD = 11.3), and median follow-up time was 56 months (P25 = 36, P75 = 84). Three (P25 = 2, P75 = 4) VFEs were performed in the first 2 years of follow-up in the overall sample, as compared to 2 VFEs (P25 = 2, P75 = 4) in patients with suspected glaucoma, and 3 VFEs (P25 = 2, P75 = 4) in those with documented glaucoma (p<0.001).

CONCLUSIONS

Based on these results, frequency of VFE in Andalusia differs from the standards recommended by the European Glaucoma Society to assess progression in the first 2 years of patient follow-up.

Accuracy of matching optic discs with visual fields: the European Structure and Function Assessment Trial (ESAFAT)

PURPOSE

To determine the ability of ophthalmologists across Europe to match stereoscopic optic disc photographs to visual fields of varying severity.

DESIGN

Evaluation and comparison of 2 diagnostic tests.

PARTICIPANTS

A total of 109 of 260 invited ophthalmologists in 11 European countries. These had participated in the previous European Optic Disc Assessment Trial (EODAT), a trial on glaucoma diagnostic accuracy based on optic discs only.

METHODS

Each participant matched stereo optic disc photographs of 40 healthy and 48 glaucomatous eyes to a visual field chosen from 4 options per disc. The 4 presented visual fields included the corresponding one and 3 other visual fields, varying in severity. The matching accuracy and any inaccuracy per disease severity were calculated. Classification accuracy (as glaucomatous or healthy) was compared with EODAT data. Duplicate slides allowed for the assessment of intraobserver agreement.

MAIN OUTCOME MEASURES

Accuracy of matching optic discs with their corresponding visual field and of classifying them as healthy or glaucomatous; intraobserver agreement (κ).

RESULTS

The overall accuracy of ophthalmologists for correctly matching stereoscopic optic disc photographs to their visual fields was 58.7%. When incorrectly matched, the observers generally overestimated the visual field severity (P<0.001), notably in eyes with early glaucoma. The intraobserver agreement was, on average, moderate (0.52).

CONCLUSIONS

European ophthalmologists correctly matched stereoscopic optic disc photographs to their corresponding visual field in only approximately 59% of cases. In most mismatches, the clinicians overestimated the visual field damage.

A survey of attitudes of glaucoma subspecialists in England and Wales to visual field test intervals in relation to NICE guidelines

OBJECTIVES

To establish the attitudes of glaucoma specialists to the frequency of visual field (VF) testing in the UK, using the NICE recommendations as a standard for ideal practice.

DESIGN

Interview and postal survey.

SETTING

UK and Eire Glaucoma Society national meeting 2011 in Manchester, UK, with a second round of surveys administered by post.

PARTICIPANTS

All consultant glaucoma specialists in England and Wales were invited to complete the survey.

PRIMARY AND SECONDARY OUTCOME MEASURES

(1) Compliance of assigned follow-up VF intervals with NICE guidelines for three hypothetical patient scenarios, with satisfactory treated intraocular pressure and (a) no evidence of VF progression; (b) evidence of VF progression and (c) uncertainty about VF progression, and respondents were asked to provide typical follow-up intervals representative of their practice; (2) attitudes to research recommendations for six VF in the first 2 years for newly diagnosed patients with glaucoma.

RESULTS

70 glaucoma specialists completed the survey. For each of the clinical scenarios a, b and c, 14 (20%), 33 (47%) and 28 (40%) responses, respectively, fell outside the follow-up interval recommended by NICE. Nearly half of the specialists (46%) agreed that 6 VF tests in the first 2 years was ideal practice, while 16 (28%) said this was practice 'not possible', with many giving resources within the NHS setting as a limiting factor.

CONCLUSIONS

The results from this survey suggest that there is a large variation in attitudes to follow-up intervals for patients with glaucoma in the UK, with assigned intervals for VF testing which are, in many cases, inconsistent with the guidelines from NICE.

Event-based progression detection strategies using scanning laser polarimetry images of the human retina

Monitoring glaucoma patients and ensuring optimal treatment requires accurate and precise detection of progression. Many glaucomatous progression detection strategies may be formulated for Scanning Laser Polarimetry (SLP) data of the local nerve fiber thickness. In this paper, several strategies, all based on repeated GDx VCC SLP measurements, are tested to identify the optimal one for clinical use. The parameters of the methods were adapted to yield a set specificity of 97.5% on real image series. For a fixed sensitivity of 90%, the minimally detectable loss was subsequently determined for both localized and diffuse loss. Due to the large size of the required data set, a previously described simulation method was used for assessing the minimally detectable loss. The optimal strategy was identified and was based on two baseline visits and two follow-up visits, requiring two-out-of-four positive tests. Its associated minimally detectable loss was 5-12 μm, depending on the reproducibility of the measurements.