Frequency of testing for detecting visual field progression

Disparities in Visual Field Testing Frequency Among Subjects With Glaucoma

Purpose

Prior evidence suggests racial disparities in the utilization of visual field testing (VFT) for the diagnosis and monitoring of glaucoma. In this study, we considered the effect of baseline glaucoma severity and socioeconomic disadvantage along with other potential confounders such as test reliability, ancillary tests, and glaucoma surgeries on racial disparity in the frequency of VFT.

Methods

The records of all subjects with a diagnosis of glaucoma who received VFT at an academic, tertiary care facility from January 2018 to December 2021 were accessed. Analysis was performed to compare VFT frequency, the total number of office visits (DoS), and the ratio of VFT frequency to DoS (VFT/DoS) across self-reported races while controlling for sex, age, socioeconomic disadvantage (Area Deprivation Index), VF reliability indicators and baseline mean deviation, optical coherence tomography frequency, and glaucoma surgeries.

Results

Among the 2654 subjects (1515 White, 782 Black, and 357 Asian) included in this study, Black subjects had the worst socioeconomic status and disease severity at baseline. They also experienced a 3% lower VFT/DoS ratio compared to White subjects (P = 0.031). Asian subjects had a 5% lower VFT/DoS ratio compared to White subjects (P = 0.015).

Discussion

We identified racial disparity in performing VFT in subjects with glaucoma even when multiple confounders were considered. Further investigation is necessary to identify other race-associated factors to work toward reducing racial disparities in VFT.

Translational Relevance

Black and Asian subjects with glaucoma receive fewer VFT per visit compared to White subjects even when considering socioeconomic disadvantage and disease severity.

Progression of Early Glaucomatous Damage: Performance of Summary Statistics From Optical Coherence Tomography and Perimetry

Purpose

Performance comparison of optical coherence tomography (OCT) and visual field (VF) summary metrics for detecting glaucomatous progression.

Methods

Thirty healthy control eyes (mean deviation [MD], -1.25 ± 2.03; pattern standard deviation [PSD] , 1.78 ± 0.77) and 91 patient eyes comprised of 54 glaucoma patients and 37 glaucoma suspects (MD, -1.58 ± 1.96; PSD, 2.82 ± 1.92) with a follow-up of at least 1 year formed a group to evaluate progression with event analyses (P-Event). A subset of eyes with an additional criterion of a minimum of four tests was used for trend analyses (P-Trend) (30 healthy controls and 73 patients). For P-Event analysis, test-retest variability thresholds (lower 5th percentile) were estimated with repeat tests within a 4-month period. A P-Event eye was considered a "progressor" if the difference between follow-up and baseline tests exceeded the variability thresholds. For the P-Trend analysis, rates of change were calculated based on least-squares regression. Negative rates with significant (P < 0.05) values were considered progressing. For a reference standard, 17 patient eyes were classified as definitely progressing based on clear evidence of structural and corresponding functional progression.

Results

Isolated OCT and VF summary metrics were either inadequately sensitive or not too specific. Combinations of OCT-OCT and OCT-VF metrics markedly improved specificity to nearly 100%. A novel combination of OCT metrics (circumpapillary retinal nerve fiber layer and ganglion cell layer) showed high precision, with 13 of the 15 statistical progressors confirmed as true positives.

Conclusions

Although relying solely on metrics is not recommended for clinical purposes, in situations requiring very high specificity and precision, combinations of OCT-OCT metrics can be used.

Translational Relevance

All available OCT and VF metrics can miss eyes with progressive glaucomatous damage and/or can falsely identify progression in stable eyes.

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.

Home-Based Perimetry for Glaucoma: Where Are We Now?

PURPOSE

To systematically summarize the current literature on home-based perimeters for glaucoma.

METHODS

A systematic review was conducted in accordance with the PRISMA-DTA checklist. Studies reporting portable perimeters designed for home use were retrieved from electronic databases and handsearching of reference lists of relevant publications. Studies reporting diagnostic accuracy data were evaluated with the QUADAS-2 tool and using standard automated perimetry as the reference standard. Other aspects of the technology such as detection of disease progression and patient acceptability were also included. Data were reported in a narrative and tabular format.

RESULTS

Of 18 included studies, 10 evaluated tablet-based perimeters, 4 evaluated web-based perimeters, and 4 evaluated head-mounted displays. Most studies used a clinic or laboratory setting. All studies reporting diagnostic accuracy data had high risk of bias in at least one domain. Across studies, sensitivity ranged from 54% in detecting mild to 91% in detecting moderate/severe glaucoma patients from controls, while specificity was between 50% and 100% for any form of glaucoma. The reported acceptability was high but had high risk of bias.

CONCLUSION

Several promising technologies designed for home-based perimetry have been reported. Current studies used a controlled setting in highly selected populations. There is uncertainty on the performance and value of home-based perimetry for glaucoma. Additional efforts are required to elucidate the ability of the home-based perimeters to detect glaucoma and disease progression in real life situations.

Trends in Utilization of Visual Field Tests for Glaucoma Patients: A Nationwide Study Using the Korean Health Insurance Review and Assessment Database

Purpose

To analyze 10-year trends in utilization of visual field tests for adult glaucoma or glaucoma-suspect patients using the Korean Health Insurance Review and Assessment data.

Methods

Health claims for the years 2010 to 2019, as recorded via Korea’s Health Insurance Review and Assessment service, were accessed. We identified glaucoma patients using the glaucoma diagnostic codes H40 (glaucoma) and H42 (glaucoma in other diseases classified elsewhere). For verification of the glaucoma diagnosis, information on any antiglaucoma medication prescriptions and ocular surgery history also was obtained. Visual field testing data was isolated using procedural codes E6690 (kinetic perimetry) and E6691 (standard automated perimetry [SAP]) performed in tertiary hospitals. Any changes in visual field test utilization were identified using regression trend analysis.

Results

From 2010 to 2019, the total number of SAP procedures performed in tertiary hospitals for either glaucoma or glaucoma-suspect patients increased gradually from 93,459 to 216,433. With regard to kinetic perimetry examinations, the total number decreased gradually from 6,364 to 3,792. The yearly average SAP number per patient showed a slight increase, from 1.168 to 1.248 (β = 0.008, R² = 0.669, p = 0.004). Meanwhile, the yearly average number of kinetic perimeter examinations per patient showed a significant decrease, from 1.093 to 0.940 (β = −0.013, R² = 0.580, p = 0.010).

Conclusions

Between 2010 and 2019, the yearly average number of SAP procedures performed per glaucoma or glaucoma-suspect patient increased in Korea. Meanwhile, the yearly average number of kinetic perimetry examinations per patient significantly decreased.

Visual field progression in Malay patients with primary glaucoma: survival analysis and prognostic factors

PURPOSE

This study aims to determine the 5-year visual field progression and identify the prognostic factors for progression in Malay patients with primary glaucoma.

METHODS

A retrospective cohort record review study was conducted among 222 patients (222 eyes) with primary glaucoma who were selected from a glaucoma research database of a tertiary center in Malaysia. The patients were Malays and diagnosed with primary open-angle glaucoma (POAG) or primary angle-closure glaucoma (PACG). Patients who were followed up regularly for at least 6 months between 1 January 2009 and 31 December 2014 and completed another 1-year follow-up after recruitment (between 1 January 2015 and 31 December 2015) were selected. Multiple prognostic factors that influence visual field progression were identified. Progression of visual field loss was based on the Advanced Glaucoma Intervention Study and Hodapp-Parrish-Anderson scores. Kaplan-Meier survival and Cox proportional hazard regression analyses were performed.

RESULTS

Sixty-three patients (28.4%) developed visual field progression after a mean (SD) follow-up of 6.9 (3.3) years. Those with POAG progressed faster (mean time, 10.6 years; 95% confidence interval [CI], 9.3, 11.9) than those with PACG (17.3 years; 95% CI, 14.8, 19.9) but not statistically significant. Disc hemorrhage and history of eye pain increased the risk of progression by 2.8-folds (95% CI, 1.6, 4.8) and 2.5-folds (1.4, 4.4), respectively.

CONCLUSION

The 5-year survival of the Malay primary glaucoma patients with visual field progression was similar with that of other Asian populations. However, aggressive management is required for those with disc hemorrhages and eye pain related to increased intraocular pressure.

Acceptability of a home-based visual field test (Eyecatcher) for glaucoma home monitoring: a qualitative study of patients' views and experiences

OBJECTIVES

To explore the acceptability of home visual field (VF) testing using Eyecatcher among people with glaucoma participating in a 6-month home monitoring pilot study.

DESIGN

Qualitative study using face-to-face semistructured interviews. Transcripts were analysed using thematic analysis.

SETTING

Participants were recruited in the UK through an advertisement in the International Glaucoma Association (now Glaucoma UK) newsletter.

PARTICIPANTS

Twenty adults (10 women; median age: 71 years) with a diagnosis of glaucoma were recruited (including open angle and normal tension glaucoma; mean deviation=2.5 to -29.9 dB).

RESULTS

All participants could successfully perform VF testing at home. Interview data were coded into four overarching themes regarding experiences of undertaking VF home monitoring and attitudes towards its wider implementation in healthcare: (1) comparisons between Eyecatcher and Humphrey Field Analyser (HFA); (2) capability using Eyecatcher; (3) practicalities for effective wider scale implementation; (4) motivations for home monitoring.

CONCLUSIONS

Participants identified a broad range of benefits to VF home monitoring and discussed areas for service improvement. Eyecatcher was compared positively with conventional VF testing using HFA. Home monitoring may be acceptable to at least a subset of people with glaucoma.

Glaucoma Home Monitoring Using a Tablet-Based Visual Field Test (Eyecatcher): An Assessment of Accuracy and Adherence Over 6 Months

Purpose

To assess accuracy and adherence of visual field (VF) home monitoring in a pilot sample of patients with glaucoma.

Design

Prospective longitudinal feasibility and reliability study.

Methods

Twenty adults (median 71 years) with an established diagnosis of glaucoma were issued a tablet perimeter (Eyecatcher) and were asked to perform 1 VF home assessment per eye, per month, for 6 months (12 tests total). Before and after home monitoring, 2 VF assessments were performed in clinic using standard automated perimetry (4 tests total, per eye).

Results

All 20 participants could perform monthly home monitoring, though 1 participant stopped after 4 months (adherence: 98% of tests). There was good concordance between VFs measured at home and in the clinic (r = 0.94, P < .001). In 21 of 236 tests (9%), mean deviation deviated by more than ±3 dB from the median. Many of these anomalous tests could be identified by applying machine learning techniques to recordings from the tablets' front-facing camera (area under the receiver operating characteristic curve = 0.78). Adding home-monitoring data to 2 standard automated perimetry tests made 6 months apart reduced measurement error (between-test measurement variability) in 97% of eyes, with mean absolute error more than halving in 90% of eyes. Median test duration was 4.5 minutes (quartiles: 3.9-5.2 minutes). Substantial variations in ambient illumination had no observable effect on VF measurements (r = 0.07, P = .320).

Conclusions

Home monitoring of VFs is viable for some patients and may provide clinically useful data.

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.

Detection of Progression With 10-2 Standard Automated Perimetry: Development and Validation of an Event-Based Algorithm

PURPOSE

To describe the development of a new algorithm for detecting progressive changes in 10-2 visual field (VF) tests using event-based analysis and to test its validity in a second, independent glaucoma cohort.

DESIGN

Prospective cohort study.

METHODS

Patients with established open-angle glaucoma from the Macular Assessment and Progression Study (MAPS; development cohort, n = 151), and the African Descent and Glaucoma Evaluation Study (ADAGES; validation cohort, n = 52) were evaluated. The 10-2 VF results from MAPS were obtained during 4 test-retest sessions within a 4-month period. For the validation analysis, 10-2 VF results from ADAGES performed on at least 5 visits were used. The event-based pointwise changes on 10-2 tests in the validation cohort were determined using 2 progression criteria: at least 3 progressing VF locations on 2 or 3 consecutive tests ("possible" or "likely" progression). Linear mixed-effects models were used to evaluate VF progression.

RESULTS

In the validation cohort, the mean (SD) follow-up time was 2.3 (0.7) years. The number of eyes experiencing 10-2 VF progression based on "possible" and "likely" progression was 36 (54.5%) and 11 (16.6%), respectively. Eyes experiencing "possible" progression had MD changes (-0.60 dB/year [95% confidence interval (CI): -0.93 to -0.28]) faster than those not meeting this criterion (P < .001), whereas for those with "likely" progression the difference was -0.91 dB/year (95% CI: -1.26 to -0.56, P < .001).

CONCLUSIONS

A new event-based progression algorithm using the 10-2 VF can identify eyes experiencing more rapid MD progression and may be used as a tool to assess progressive macular functional changes in glaucoma.

Quantification of Visual Field Variability in Glaucoma: Implications for Visual Field Prediction and Modeling

Purpose

To quantify visual field (VF) variability as a function of threshold sensitivity and location, and to compare weighted pointwise linear regression (PLR) with unweighted PLR and pointwise exponential regression (PER) for data fit and prediction ability.

Methods

Two datasets were used for this retrospective study. The first was used to characterize and estimate VF variability, and included a total of 4,747 eyes of 3,095 glaucoma patients with six or more VFs and 3 years or more of follow-up. After performing PER for each series, standard deviation of residuals was quantified for each decibel of sensitivity as a measure of variability. A separate dataset was used to test and compare unweighted PLR, weighted PLR, and PER for data fit and prediction, and included 261 eyes of 176 primary open-angle glaucoma patients with 10 or more VFs and 6 years or more of follow-up.

Results

The degree of variability changed as a function of threshold sensitivity with a zenith and a nadir at 33 and 11 dB, respectively. Variability decreased with eccentricity and was higher in the central 10° (P < 0.001). Differences among the methods for data fit were negligible. PER was the best model to predict future sensitivity values in the mid term and long term.

Conclusions

VF variability increases with the severity of glaucoma damage and decreases with eccentricity. Weighted linear regression neither improves model fit nor prediction. PER exhibited the best prediction ability, which is likely related to the nonlinear nature of long-term glaucomatous perimetric decay.

Translational Relevance

This study suggests that taking into account heteroscedasticity has no advantage in VF modeling.

Visual Defects and Ageing

Many diseases are related to age, among these neurodegeneration is particularly important. Alzheimer's disease Parkinson's and Glaucoma have many common pathogenic events including oxidative damage, Mitochondrial dysfunction, endothelial alterations and changes in the visual field. These are well known in the case of glaucoma, less in the case of neurodegeneration of the brain. Many other molecular aspects are common, such as the role of endoplasmic reticulum autophagy and neuronal apoptosis while others have been neglected due to lack of space such as inflammatory cytokine or miRNA. Moreover, the loss of specific neuronal populations, the induction of similar mechanisms of cell injury and the deposition of protein aggregates in specific anatomical areas are very similar events between these diseases. Intracellular and/or extracellular accumulation of protein aggregates is a key feature of many neurodegenerative disorders. The existence of abnormal protein aggregates has been documented in the RGCs of glaucomatous patients such as the anomalous Tau protein or the β-amyloid accumulations. Intra-cell catabolic processes also appear to be common in both glaucoma and neurodegeneration. They also help us to understand how the basis between these diseases is common and how the visual aspects can be a serious problem for those who are affected.

Detection of Longitudinal Visual Field Progression in Glaucoma Using Machine Learning

PURPOSE

Global indices of standard automated perimerty are insensitive to localized losses, while point-wise indices are sensitive but highly variable. Region-wise indices sit in between. This study introduces a machine learning-based index for glaucoma progression detection that outperforms global, region-wise, and point-wise indices.

DESIGN

Development and comparison of a prognostic index.

METHOD

Visual fields from 2085 eyes of 1214 subjects were used to identify glaucoma progression patterns using machine learning. Visual fields from 133 eyes of 71 glaucoma patients were collected 10 times over 10 weeks to provide a no-change, test-retest dataset. The parameters of all methods were identified using visual field sequences in the test-retest dataset to meet fixed 95% specificity. An independent dataset of 270 eyes of 136 glaucoma patients and survival analysis were used to compare methods.

RESULTS

The time to detect progression in 25% of the eyes in the longitudinal dataset using global mean deviation (MD) was 5.2 (95% confidence interval, 4.1-6.5) years; 4.5 (4.0-5.5) years using region-wise, 3.9 (3.5-4.6) years using point-wise, and 3.5 (3.1-4.0) years using machine learning analysis. The time until 25% of eyes showed subsequently confirmed progression after 2 additional visits were included were 6.6 (5.6-7.4) years, 5.7 (4.8-6.7) years, 5.6 (4.7-6.5) years, and 5.1 (4.5-6.0) years for global, region-wise, point-wise, and machine learning analyses, respectively.

CONCLUSIONS

Machine learning analysis detects progressing eyes earlier than other methods consistently, with or without confirmation visits. In particular, machine learning detects more slowly progressing eyes than other methods.

Impact of optic disc hemorrhage on subsequent glaucoma progression in mild-to-moderate myopia

PURPOSE

To investigate optic disc hemorrhage (DH)'s clinical implications to subsequent progression of primary open-angle glaucoma (POAG) in cases of mild-to-moderate myopia.

DESIGN

Retrospective comparative study.

PARTICIPANTS

(1) Fifty-nine (59) myopic (26.5 mm > axial length [AXL] ≥ 24.0 mm) POAG patients with DH and (2) 59 age-, AXL-, and mean deviation (MD) of visual field (VF)-matched controls without DH were evaluated over the course of a minimum 3.5 years of follow up. For clear assessment of the effect of DH on progression of glaucoma, the patients selected for inclusion in the study were those with stable IOP (i.e., those showing an at least 20% reduction relative to the baseline IOP) whose IOP-lowering medication was not increased, supplemented or changed during the follow-up period.

METHODS

The patients' optic disc/retinal nerve fiber layer (RNFL) photographs were independently evaluated by three glaucoma specialists for structural progression of glaucoma. Event-based analysis with Guided Progression Analysis (GPA) software was used to determine their functional progression. The durations of structural and functional progression were compared by Kaplan-Meier life survival analyses.

MAIN OUTCOME MEASURES

Optic disc/RNFL progression and VF progression.

RESULTS

The mean follow-up periods between the DH and non-DH groups were not significantly different: in the DH group, 5.6±2.7 years; in the non-DH group, 5.4±2.6 years (P = 0.588). In the DH group, 30 (50.8%) of 59 eyes manifested optic disc/RNFL deterioration; in the non-DH group, however, only 17 (28.8%) of 59 eyes showed structural progression. For the DH group, the cumulative probability of structural glaucoma progression was significantly greater than for the non-DH group (P = 0.001; log rank test). Interestingly, the two groups did not significantly differ in the cumulative probability of functional progression (P = 0.79; log rank test): in the DH group, VF progression was observed in 14 eyes (23.7%); in the non-DH group, in 12 eyes (20.3%).

CONCLUSIONS

DH was associated with a greater probability of structural progression in medically well-controlled-IOP POAG eyes with mild-to-moderate myopia. However, the relevance of DH to VF progression was not clear over the course of the average 5.5-year duration of the study.

Impact of Normal Aging and Progression Definitions on the Specificity of Detecting Retinal Nerve Fiber Layer Thinning

PURPOSE

To evaluate the specificity of current definitions used to identify progressive change of the average peripapillary retinal nerve fiber layer (RNFL) thickness measurements obtained on optical coherence tomography (OCT) imaging.

DESIGN

Prospective observational cohort study.

METHODS

Setting: University of California, San Diego.

STUDY POPULATION

Seventy-five eyes from 45 normal participants.

OBSERVATION PROCEDURE

Patients were seen at an average of 5.7 visits over 3.2 years, to determine the age-related average RNFL thickness changes and longitudinal measurement variability. Slope and variability estimates were used to reconstruct "real-world" OCT imaging measurements with computer simulations.

MAIN OUTCOME MEASURE

False-positive rates for progression in normal eyes using different definitions.

RESULTS

The estimated normal average RNFL thickness change over time was -0.54 ± 0.23 μm/year (P < .001). Even with a recent definition of progression that appeared to guarantee a high level of specificity by accounting for normal aging (requiring a significant negative slope that was more negative than the 5% lower limit of aging), 18% simulated normal eyes were still falsely identified as having progressed after 5 years of annual testing in a clinical practice scenario. However, this was reduced to 8% and 4% when trend-based analysis of progression was performed after adjustments using the mean and 5% lower limit of normal rates of aging, respectively.

CONCLUSIONS

This study highlights how current definitions for detecting RNFL thinning have an unacceptably poor level of specificity, and that more stringent definitions are required to avoid misleading interpretations of progression on OCT imaging in clinical practice.

Risk Factors for Rapid Glaucoma Disease Progression

PURPOSE

To determine the intraocular and systemic risk factor differences between a cohort of rapid glaucoma disease progressors and nonrapid disease progressors.

DESIGN

Retrospective case-control study.

METHODS

Setting: Five private ophthalmology clinics.

STUDY POPULATION

Forty-eight rapidly progressing eyes (progression ≥1 dB mean deviation [MD]/year) and 486 non-rapidly progressing eyes (progression <1 dB MD/year). Patients were eligible if they had a diagnosis of glaucoma from their ophthalmologist and if they had greater than or equal to 5 Humphrey visual fields (24-2) conducted. Patients were excluded if their sequential visual fields showed an improvement in MD or if they had greater than 5 dB MD variation in between visits. Patients with obvious neurologic fields were excluded.

OBSERVATION PROCEDURE

Clinical and demographic data (age, sex, central corneal thickness [CCT], intraocular pressure [IOP], refraction, medications), as well as medical, surgical, and ocular histories, were collected.

MAIN OUTCOME MEASURES

Risk factor differences between the cohorts were measured using the independent t test, Wald χ², and binomial regression analysis.

RESULTS

Rapid progressors were older, had significantly lower CCT and baseline IOPs, and were more likely to have pseudoexfoliation, disc haemorrhages, ocular medication changes, and IOP-lowering surgery. They also had significantly higher rates of cardiovascular disease and hypotension. Subjects with cardiovascular disease were 2.33 times more likely to develop rapidly progressive glaucoma disease despite significantly lower mean and baseline IOPs.

CONCLUSION

Cardiovascular disease is an important risk factor for rapid glaucoma disease progression irrespective of IOP control.

Detection of Functional Change Using Cluster Trend Analysis in Glaucoma

Purpose

Global analyses using mean deviation (MD) assess visual field progression, but can miss localized changes. Pointwise analyses are more sensitive to localized progression, but more variable so require confirmation. This study assessed whether cluster trend analysis, averaging information across subsets of locations, could improve progression detection.

Methods

A total of 133 test-retest eyes were tested 7 to 10 times. Rates of change and P values were calculated for possible re-orderings of these series to generate global analysis ("MD worsening faster than x dB/y with P < y"), pointwise and cluster analyses ("n locations [or clusters] worsening faster than x dB/y with P < y") with specificity exactly 95%. These criteria were applied to 505 eyes tested over a mean of 10.5 years, to find how soon each detected "deterioration," and compared using survival models. This was repeated including two subsequent visual fields to determine whether "deterioration" was confirmed.

Results

The best global criterion detected deterioration in 25% of eyes in 5.0 years (95% confidence interval [CI], 4.7-5.3 years), compared with 4.8 years (95% CI, 4.2-5.1) for the best cluster analysis criterion, and 4.1 years (95% CI, 4.0-4.5) for the best pointwise criterion. However, for pointwise analysis, only 38% of these changes were confirmed, compared with 61% for clusters and 76% for MD. The time until 25% of eyes showed subsequently confirmed deterioration was 6.3 years (95% CI, 6.0-7.2) for global, 6.3 years (95% CI, 6.0-7.0) for pointwise, and 6.0 years (95% CI, 5.3-6.6) for cluster analyses.

Conclusions

Although the specificity is still suboptimal, cluster trend analysis detects subsequently confirmed deterioration sooner than either global or pointwise analyses.

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.

The Use of Microperimetry to Detect Functional Progression in Non-Neovascular Age-Related Macular Degeneration: A Systematic Review

We reviewed the current literature on the ability of microperimetry to detect non-neovascular age-related macular degeneration (AMD) disease progression. The index test was retinal sensitivity measurement assessed by microperimetry and comparators were other functional measures (best-corrected and low-luminance visual acuities, and fixation stability) and structural parameters [retinal thickness, choroidal thickness, and area of geographic atrophy (GA) determined by color fundus photographs, short-wave or near-infrared fundus autofluorescence]. The reference standard was area of GA. The literature search was conducted in January 2016 and included MEDLINE, EMBASE, the Cochrane Library, Biosis, Science Citation Index, ProQuest Health and Medicine, CINAHL, and Highwire Press. We included 6 studies that enrolled 41 eyes with intermediate AMD (from a single study) and 80 eyes with GA secondary to AMD. Retinal sensitivity measured by microperimetry was the only functional measure that consistently detected progression in each cohort. Insufficient reported data precluded meta-analysis. Various microperimetry parameters were used to assess cohort-level change in retinal sensitivity, but the methods of analysis have yet to mature in complexity in comparison with established glaucoma field progression analysis. Microperimetry-assessed retinal sensitivity measurement may be more sensitive in detecting progression than other functional measures in non-neovascular AMD. However, the lack of standardized testing protocol and methods of progression analysis hindered comparison. Harmonization of testing protocol and development of more robust methods of analyzing raw microperimetric data will facilitate clinical implementation of this valuable retinal assessment tool.

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.

Detection and measurement of clinically meaningful visual field progression in clinical trials for glaucoma

Glaucomatous visual field progression has both personal and societal costs and therefore has a serious impact on quality of life. At the present time, intraocular pressure (IOP) is considered to be the most important modifiable risk factor for glaucoma onset and progression. Reduction of IOP has been repeatedly demonstrated to be an effective intervention across the spectrum of glaucoma, regardless of subtype or disease stage. In the setting of approval of IOP-lowering therapies, it is expected that effects on IOP will translate into benefits in long-term patient-reported outcomes. Nonetheless, the effect of these medications on IOP and their associated risks can be consistently and objectively measured. This helps to explain why regulatory approval of new therapies in glaucoma has historically used IOP as the outcome variable. Although all approved treatments for glaucoma involve IOP reduction, patients frequently continue to progress despite treatment. It would therefore be beneficial to develop treatments that preserve visual function through mechanisms other than lowering IOP. The United States Food and Drug Administration (FDA) has stated that they will accept a clinically meaningful definition of visual field progression using Glaucoma Change Probability criteria. Nonetheless, these criteria do not take into account the time (and hence, the speed) needed to reach significant change. In this paper we provide an analysis based on the existing literature to support the hypothesis that decreasing the rate of visual field progression by 30% in a trial lasting 12-18 months is clinically meaningful. We demonstrate that a 30% decrease in rate of visual field progression can be reliably projected to have a significant effect on health-related quality of life, as defined by validated instruments designed to measure that endpoint.

Management of advanced glaucoma: Characterization and monitoring

Recent advances in glaucoma diagnosis focus on diagnosing the disease in early stages. Despite the importance of such efforts, a meaningful proportion of patients present in advanced stages. The cost for treatment and monitoring of advanced glaucoma often exceeds that with earlier disease, not to mention the significant effect of visual impairment on quality of life. Moreover, structural and functional tests used to monitor changes encounter technical limitations in advanced cases that can delay detection of true progression. New technologies and methods to analyze longitudinal data may prove helpful for monitoring patients with advanced glaucoma and reduce the burdens of the disease.

Evaluation of the progression of visual field damage in patients suffering from early manifest glaucoma

BACKGROUND

This retrospective study aimed to determine how often a perimetric examination should be carried out in order to identify visual field (VF) changes in patients with relatively early manifestation glaucoma.

MATERIALS AND METHODS

Patients included had a relatively recent manifestation of primary open-angle glaucoma. Patients with a minimum follow-up of 5 years and a minimum of seven VF tests were included. Statistical analysis was performed to verify the trend of variations in mean defect (MD) over time (PeriData). The results were subjected to a t-test for a comparative analysis of progression of VF changes over time. The annual rate of progression provided by PeriData considering all the VFs analyzed was compared with that obtained on half of the VF examinations during the same follow-up period. An analysis of the MD trend over time was also carried out in relationship to the number of VF tests done and by dividing the sample into a high-frequency group (more than eight VFs) and a low-frequency group (fewer than eight VFs) in the follow-up period.

RESULTS

A total of 96 eyes of 96 patients were included, and overall 846 VFs were examined. The paired t-test performed comparing the MD index of all the VFs against half of them did not show statistical significance (P=0.537). The high-frequency group comprised 39 eyes (average VF 11.05±1.91, average time interval 0.76 years) while the low-frequency group comprised 57 eyes (average VF 6.95±0.6, average time interval 1.21 years). The analysis of the MD trend in the high-frequency patients showed significance (P=0.017); the low-frequency group did not show statistical significance (P=0.08).

CONCLUSION

The number of VFs in a determined time interval was not significant. However, a greater frequency of tests provides a predictive evaluation of the rate of progression of early manifestation open-angle glaucoma.

A Two-step Estimation Approach for Logistic Varying Coefficient Modeling of Longitudinal Data

Varying coefficient models are useful for modeling longitudinal data and have been extensively studied in the past decade. Motivated by commonly encountered dichotomous outcomes in medical and health cohort studies, we propose a two-step method to estimate the regression coefficient functions in a logistic varying coefficient model for a longitudinal binary outcome. The model depicts time-varying covariate effects without imposing stringent parametric assumptions. The proposed estimation is simple and can be conveniently implemented using existing statistical packages such as SAS and R. We study asymptotic properties of the proposed estimators which lead to asymptotic inference and also develop bootstrap inferential procedures to test whether the coefficient functions are indeed time-varying or are equal to zero. The proposed methodology is illustrated with the analysis of a smoking cessation data set. Simulations are used to evaluate the performance of the proposed method compared to an alternative estimation method based on local maximum likelihood.

Qualitative investigation of patients' experience of a glaucoma virtual clinic in a specialist ophthalmic hospital in London, UK

OBJECTIVES

To explore how patients felt about delivery of care in a novel technician-delivered virtual clinic compared with delivery of care in a doctor-delivered model.

DESIGN

A qualitative investigation using one-to-one interviews before and after patients' appointments at either the standard outpatient glaucoma clinic or the new technician-delivered virtual glaucoma clinic (Glaucoma Screening and Stable Monitoring Service, GSMS).

SETTING

A glaucoma clinic based in a tertiary ophthalmic specialist hospital in London.

PARTICIPANTS

43 patients (38 Caucasian, 5 African/Afro-Caribbean) were interviewed prior to their glaucoma appointment; 38 patients were interviewed between 4 and 6 weeks after their appointment. Consecutive patients were identified from patient reception lists and telephoned prior to their appointment inviting them to participate.

RESULTS

Trust in the patient-provider relationship emerged as a key theme in patients' acceptance of not being seen in a traditional doctor-delivered service. Patients who were well informed regarding their glaucoma status and low risk of progression to sight loss were more accepting of the GSMS. Patients valued the reassurance received through effective communication with their healthcare practitioner at the time of their appointment.

CONCLUSIONS

This study suggests that patients are accepting of moving to a model of service delivery whereby the doctor is removed from the consultation as long as they are informed about the status of their condition and reassured by the interaction with staff they meet. This study highlights the importance of patient engagement when introducing new models of service delivery.

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.

Assessment of the reliability of standard automated perimetry in regions of glaucomatous damage

PURPOSE

Visual field testing uses high-contrast stimuli in areas of severe visual field loss. However, retinal ganglion cells saturate with high-contrast stimuli, suggesting that the probability of detecting perimetric stimuli may not increase indefinitely as contrast increases. Driven by this concept, this study examines the lower limit of perimetric sensitivity for reliable testing by standard automated perimetry.

DESIGN

Evaluation of a diagnostic test.

PARTICIPANTS

A total of 34 participants with moderate to severe glaucoma; mean deviation at their last clinic visit averaged -10.90 dB (range, -20.94 to -3.38 dB). A total of 75 of the 136 locations tested had a perimetric sensitivity of ≤ 19 dB.

METHODS

Frequency-of-seeing curves were constructed at 4 nonadjacent visual field locations by the Method of Constant Stimuli (MOCS), using 35 stimulus presentations at each of 7 contrasts. Locations were chosen a priori and included at least 2 with glaucomatous damage but a sensitivity of ≥ 6 dB. Cumulative Gaussian curves were fit to the data, first assuming a 5% false-negative rate and subsequently allowing the asymptotic maximum response probability to be a free parameter.

MAIN OUTCOME MEASURES

The strength of the relation (R(2)) between perimetric sensitivity (mean of last 2 clinic visits) and MOCS sensitivity (from the experiment) for all locations with perimetric sensitivity within ± 4 dB of each selected value, at 0.5 dB intervals.

RESULTS

Bins centered at sensitivities ≥ 19 dB always had R(2) >0.1. All bins centered at sensitivities ≤ 15 dB had R(2) <0.1, an indication that sensitivities are unreliable. No consistent conclusions could be drawn between 15 and 19 dB. At 57 of the 81 locations with perimetric sensitivity <19 dB, including 49 of the 63 locations ≤ 15 dB, the fitted asymptotic maximum response probability was <80%, consistent with the hypothesis of response saturation. At 29 of these locations the asymptotic maximum was <50%, and so contrast sensitivity (50% response rate) is undefined.

CONCLUSIONS

Clinical visual field testing may be unreliable when visual field locations have sensitivity below approximately 15 to 19 dB because of a reduction in the asymptotic maximum response probability. Researchers and clinicians may have difficulty detecting worsening sensitivity in these visual field locations, and this difficulty may occur commonly in patients with glaucoma with moderate to severe glaucomatous visual field loss.

A qualitative investigation into patients' views on visual field testing for glaucoma monitoring

OBJECTIVES

To investigate the views and experiences of patients regarding their glaucoma follow-up, particularly towards the type and frequency of visual field (VF) testing.

DESIGN

A qualitative investigation using focus groups. The group discussion used broad open questions around the topics in a prompt guide relating to experiences of glaucoma follow-up, and in particular, VF monitoring. All the groups were taped, transcribed and coded using manual and computer-aided methods.

SETTING

Three National Health Service (NHS) hospitals in England; two focus groups took place at each hospital.

PARTICIPANTS

28 patients (mean (SD) age: 74 (9) years; 54% women) diagnosed with glaucoma for at least 2 years. Each focus group consisted of 3-6 patients.

PRIMARY AND SECONDARY OUTCOMES

(1) Attitudes and experiences of patients with glaucoma regarding VF testing. (2) Patients' opinions about successful follow-up in glaucoma.

RESULTS

These patients did not enjoy the VF test but they recognised the importance of regular monitoring for preserving their vision. These patients would agree to more frequent VF testing on their clinician's recommendation. A number of themes recurred throughout the focus groups representing perceived barriers to follow-up care. The testing environment, waiting times, efficiency of appointment booking and travel to the clinic were all perceived to influence the general clinical experience and the quality of assessment data. Patients were also concerned about aspects of patient-doctor communication, and often received little to no feedback about their results.

CONCLUSIONS

Patients trust the clinician to make the best decisions for their glaucoma follow-up. However, patients highlighted a number of issues that could compromise the effectiveness of VF testing. Addressing patient-perceived barriers could be an important step for devising optimal strategies for follow-up care.

New insights into measurement variability in glaucomatous visual fields from computer modelling

OBJECTIVE

To develop a model to simulate visual fields (VFs) in glaucoma patients, and to characterize variability of the Mean Deviation (MD) VF summary measurement using real VFs and simulations.

METHODS

Pointwise VF variability was previously approximated using longitudinal VF data (24-2 SITA Standard, Humphrey Field Analyzer) from 2,736 patients; these data were used to build a non-parametric model to simulate VFs. One million VF simulations were generated from 1,000 VFs (1,000 simulations per 'ground-truth' VF), and the variability of simulated MDs was characterized as a function of ground-truth MD and Pattern Standard Deviation (PSD).

RESULTS

The median (interquartile range, IQR) patient age and MD was 66 (56 to 75) years and -3.5 (-8.3 to -1.1) decibels, respectively. The inferred variability as a function of ground-truth MD and PSD indicated that variability, on average, increased rapidly as glaucoma worsened. However, the pattern of VF damage significantly affects the level of MD variability, with more than three-fold differences between patients with approximately the same levels of MD but different patterns of loss.

CONCLUSIONS

A novel approach for simulating VFs is introduced. A better understanding of VF variability will help clinicians to differentiate real VF progression from measurement variability. This study highlights that, overall, MD variability increases as the level of damage increases, but variability is highly dependent on the pattern of VF damage. Future research, using VF simulations, could be employed to provide benchmarks for measuring the performance of VF progression detection algorithms and developing new strategies for measuring VF progression.

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.

Comparison of neuroretinal rim area measurements made by the Heidelberg Retina Tomograph I and the Heidelberg Retina Tomograph II

PURPOSE

To investigate the agreement between neuroretinal rim area (RA) measurements using the Heidelberg Retina Tomograph I (HRT Classic) and Heidelberg Retina Tomograph II (HRT II). To compare apparent RA changes in follow-up series of HRT II topographies when using either an HRT Classic or HRT II mean topography as baseline.

DESIGN

Cross-sectional study and "no-change," short time series study.

PARTICIPANTS

Forty-three ocular hypertensive and 31 primary open angle glaucoma subjects.

METHODS

Five HRT Classic and 5 HRT II examinations were acquired from 1 eye of each subject, across 2 visits within 6 weeks. For the cross-sectional study, follow-up RA measurements from HRT Classic and HRT II were compared, using the same HRT Classic mean topography as the baseline. The linear rates of RA change were compared in 2 short time series with either an HRT Classic or an HRT II mean topography as baseline, and 4 follow-up HRT II mean topographies. Intervals between topographies were arbitrarily set at 1 year for meaningful comparisons of rates. Rates of RA change over time were calculated by linear regression. Separate analyses were performed using 3 available reference planes (RP).

MAIN OUTCOME MEASURES

Global and sectoral RA measurements in HRT Classic and HRT II mean topographies; linear rates of RA change.

RESULTS

HRT Classic minus HRT II mean differences (95% limits of agreement) were 0.09 (-0.17, 0.35) mm, 0.09 (-0.13, 0.32) mm, and 0.11 (-0.24, 0.46) mm for the Moorfields, 320 µm, and standard RPs, respectively (P<0.001 for all RPs, Wilcoxon rank sum test). In the time series, the mean differences (95% limits of agreement) of RA rates of change (HRT Classic baseline minus HRT II baseline) were -0.01 (-0.06, 0.03) mm/y, -0.01 (-0.06, 0.04) mm/y, and -0.0 (-0.09, 0.05) mm/y using the Moorfields, 320 µm, and standard RPs, respectively.

CONCLUSION

Although HRT software is backward-compatible, follow-up RA measurements made in the same eye using HRT Classic and HRT II devices display statistically and clinically meaningful systematic differences when HRT Classic topographies are used as a baseline.

Specificity of the program threshold noiseless trend for perimetric progression analysis

PURPOSE

To evaluate the specificity of the Threshold Noiseless Trend program (TNT), designed to measure progression in visual fields, using four procedures.

MATERIALS AND METHODS

A. In 63 eyes with ocular hypertension, whose last examination showed no perimetric or morphological defects, we performed a mean of 7.70 +/- 1.71 follow-up examinations during 2.2 +/- 0.6 years. B. In 81 glaucomatous eyes examined twice with a bracketing strategy (Octopus 1-2-3 perimeter), we calculated mean threshold value and long-term fluctuation. We simulated 12 different visual fields, adding a random component to simulate an equivalent fluctuation of amplitude. C. Seventy-two glaucomatous eyes, with and without progression, were examined 7.76 +/- 1.25 times during 4.88 +/- 1.39 years using the Humphrey-Sita Standard strategy. Visual field tests were randomly disordered and analyzed using TNT. D. 1221 eyes were examined 7.19 +/- 3.5 times during 3.50 +/- 1.45 years (10,407 visual fields) using TOP-G1 program. We detected progression in 204 eyes using TNT. They were re-evaluated after random disordering of visual field tests.

RESULTS

The four procedures indicated specificity > or = 95% as from the seventh examination; this reduced to 90% in experiment C with six examinations, and in experiments A and C with five examinations.

CONCLUSIONS

The specificity of TNT may be considered to be over 95% with a large number of examinations, and 90-100% with fewer examinations. At least five examinations are required for a basic interpretation of progression, and preferably more than six to guarantee the specificity of the result.

A critical discussion of the rates of progression and causes of optic nerve damage in glaucoma: International Glaucoma Think Tank II: July 25-26, 2008, Florence, Italy

The International Glaucoma Think Tank II brought together glaucoma clinicians and researchers from all over the world to discuss current practices in glaucoma diagnosis and management, and the neurobiology of glaucoma. The meeting focused on several themes, including rates of deterioration in glaucoma patients, mechanisms of optic nerve damage, and implications for treatment. Issues such as how to measure and integrate progression information into clinical practice, screening protocols, or trials were discussed, as were promising new technologies and limitations of currently available measurement tools. Clinical applications for genetic testing were considered. Study of the neurobiology of glaucoma continues to inform our understanding of underlying degenerative processes, as well as to introduce possibilities for early detection or prevention. Many questions regarding glaucoma pathophysiology and best treatment practices remain unanswered, but with continued research and discussion, we will advance our understanding of this disease and ensure that patients receive optimal care.

Glaucoma: an area of darkness

This review of Primary Open Angle Glaucoma looks at the management of the condition today. It does this by looking at the following areas: (a) the size of the problem; (b) the position of IOP, with respect to its elevation and fluctuation; (c) optic nerve head changes; and (d) visual function changes. In doing so, it contrasts what is known now with ideas and concepts that were prevalent at the time of the two previous Bowman lecturers, Duke Elder and Drance, as well as noting concepts about the disease that were current at the time of William Bowman. The review concludes by suggesting challenges in this area that lie ahead.

A two-stage neural spiking model of visual contrast detection in perimetry

Perimetry is a commonly used clinical test for visual function, limited by high variability. The sources of this variability need to be better understood. In this paper, we investigate whether noise intrinsic to neural firing could explain the variability in normal subjects. We present the most physiologically accurate model to date for stimulus detection in perimetry combining knowledge of the physiology of components of the visual system with signal detection theory, and show that it requires that detection be mediated by multiple cortical cells in order to give predictions consistent with psychometric functions measured in human observers.

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

BACKGROUND

This study aimed to gain insight into the optimal spacing in time for visual field tests for progression detection in glaucoma.

METHODS

Three perimetric strategies for progression detection were compared by means of simulation experiments in a theoretical cohort. In strategies 1 and 2, visual field testing was performed with fixed-spaced inter-test intervals, using intervals of 3 and 6 months respectively. In strategy 3, the inter-test interval was kept at 1 year as long as the fields appeared unchanged. Then, as soon as progression was suspected, confirmation or falsification were performed promptly. Follow-up fields were compared against a baseline assuming linear deterioration, using various progression criteria. Outcome measures were: (1) specificity, (2) time delay until the diagnosis of definite progression, and (3) number of required tests.

RESULTS

Strategies 2 and 3 had a higher specificity than strategy 1. Strategies 1 and 3 detected progression earlier than strategy 2. The number of required visual field tests was lowest for strategy 3.

CONCLUSION

Perimetry in glaucoma can be optimised by postponing the next test under apparently stable field conditions and bringing the next test forward once progression is suspected.

Modeling the sensitivity to variability relationship in perimetry

PURPOSE

Studies in glaucoma patients show that standard automated perimetry results increase in variability as sensitivity decreases. However, the reasons for this change are unclear. This study presents the principle of Divergent Dysfunction as a possible explanation for this change in variability, and incorporates it into a model that can be used to simulate perimetry.

METHODS

A computer program was written to simulate visual field test results based on the model, using a Full Threshold testing strategy. The validity of the simulation was tested by comparing it with normal sensitivity values, and with test-retest data from 63 participants evaluated five times each over the course of 1 month. The effect on the simulated data of varying parameters of the model was investigated, such as changing the magnitude of variability and the percentages of false positive and negative responses.

RESULTS

The correlation between subject and simulated test-retest data was 0.987. Several factors were found to affect the sensitivity-variability relationship for the simulated data, most notably the rate of sensitivity decline, the percentage of false positives, and the starting luminance of the test procedure.

CONCLUSIONS

The principle of Divergent Dysfunction presented here provides a plausible explanation for the sensitivity-variability relationship for standard automated perimetry in glaucomatous eyes. The model and resultant simulation program aim to provide an intuitive demonstration of the principle, which can also be used to examine the effectiveness of different testing strategies. These findings have great implications for future clinical research.

Towards an optimal perimetric strategy for progression detection in glaucoma: from fixed-space to adaptive inter-test intervals

BACKGROUND

The aim was to compare two perimetric strategies for progression detection in glaucoma.

METHODS

Two perimetric strategies for progression detection were compared by means of a thought experiment in a theoretical cohort. In strategy I, visual field testing is performed with fixed-space inter-test intervals at a frequency of two tests per year. In strategy II, the frequency of visual field testing is set to one test per year as long as the fields are apparently unchanged, whereas as soon as progression is suspected, confirmation or falsification is performed within a short time span. Outcome measures were the time delay between the progression event and the diagnosis of definite progression, and the number of visual field tests performed per patient per year.

RESULTS

Average time delay between the actual progression event and the final diagnosis of definite progression was 15 months in the case of strategy I and 6 months in the case of strategy II. Maximum time delays were 18 and 12 months respectively. The frequency of visual field testing was 2 tests per patient per year for strategy I and 1.45 tests per patient per year for strategy II.

CONCLUSIONS

Perimetry in glaucoma can be optimised by postponing the next test in the case of an apparently stable field and accelerating the next test in the case of a suspected progression. This results in an earlier diagnosis, a lower perimetric frequency and a shorter period of uncertainty for the patient.

Bayes' theorem applied to perimetric progression detection in glaucoma: from specificity to positive predictive value

PURPOSE

To estimate the specificity of a clinical evaluation of a series of visual fields and to calculate the positive predictive value of progression.

METHODS

The specificity of a clinical evaluation of a series of visual fields was estimated using nonparametric ranking and probability calculus. The positive predictive value of progression was calculated using Bayes' theorem. The literature suggests a prior probability of progression of typically 0.10 in the case of one visual field per year. Three different prior probability values were used: 0.05, 0.10, and 0.20. Calculations were performed for a sensitivity of 0.50, 0.80, and 1.00.

RESULTS

Specificity of a clinical evaluation of a series of visual fields was calculated as 0.83 for four fields (two baseline fields, one follow-up field with suspected progression, and one confirmation of the suspected progression), 0.90 for five fields, and 0.95 for six fields. Positive predictive values ranged from 0.14 to 0.83. Positive predictive value was approximately 0.5 for a prior probability of 0.10, a sensitivity of 0.80, and a specificity of 0.90.

CONCLUSIONS

Realistic series of visual fields that are apparently progressive have a positive predictive value of typically 0.5, i.e., half of them are stable. In the case of a high prior probability (uncontrolled glaucoma or long interval between successive fields), four fields may suffice to diagnose progression, whereas at least six fields are required if the prior probability is low.

Predictive factors for glaucomatous visual field progression in the Advanced Glaucoma Intervention Study

PURPOSE

To investigate the risk factors associated with visual field (VF) progression in the Advanced Glaucoma Intervention Study (AGIS) with pointwise linear regression (PLR) analysis of serial VFs.

DESIGN

Prospective, multicenter, randomized clinical trial.

PARTICIPANTS

Five hundred nine eyes of 401 patients from the AGIS with a baseline VF score of <or=16, >or=7 VF examinations, and >or=3 years of follow-up were selected.

MAIN OUTCOME MEASURE

Visual field progression.

METHODS

This is a cohort study of patients enrolled in a prospective randomized clinical trial (AGIS). Worsening of a test location on PLR analysis was defined as a change of threshold sensitivity of >or=1.00 decibels a year, with P<or=0.01. Visual field progression was defined as worsening of at least 2 test locations within a Glaucoma Hemifield Test cluster with PLR analysis. Multivariate logistic regression was used to determine risk factors associated with VF worsening. Intraocular pressure (IOP) fluctuation was defined as standard deviation of the IOP at all visits after the initial surgery.

RESULTS

The mean (+/- standard deviation) follow-up time and baseline AGIS score were 7.4 (+/-1.7) years and 7.7 (+/-4.4), respectively. Visual field progression was detected with PLR analysis in 151 eyes (30%). Older age at the initial intervention (P = 0.0012; odds ratio [OR], 1.30; 95% confidence interval [CI], 1.11-1.50), larger IOP fluctuation (P = 0.0013; OR, 1.31; 95% CI, 1.12-1.54), increasing number of glaucoma interventions (P = 0.01; OR, 1.74; 95% CI, 1.14-2.64), and longer follow-up (P = 0.02; OR, 1.19; 95% CI, 1.03-1.38) were associated with increased odds of VF progression. When regression analyses were repeated in eyes with and without a history of cataract extraction, IOP fluctuation was the only variable to be consistently associated with VF progression.

CONCLUSION

Both increasing age and greater IOP fluctuation increase the odds of VF progression by 30% (for each 5-year increment in age and 1-mmHg increase in IOP fluctuation). The higher risk conferred by IOP fluctuation was consistently observed in eyes with and without a history of cataract extraction.

Reducing noise in suspected glaucomatous visual fields by using a new spatial filter

Visual field testing with automated perimetry is hampered by the amount of noise present in the readings. Here, we derive a physiologically accurate spatial filter to be applied to the data after patient examination. The filter was tested by a Virtual Eye computer simulation. By simulating series of stable fields it was shown that specificity of determining visual field changes was improved; while simulating progressing fields (based on a map of the optic nerve head) it was shown that sensitivity was also improved. The filter appears to reduce the noise in glaucomatous visual field data and may be clinically useful.