New perimetric threshold test algorithm with dynamic strategy and tendency oriented perimetry (TOP) in glaucomatous eyes

Screening for Glaucomatous Visual Field Defects in Rural Australia with an iPad

Aim and objective

Developing improved methods for early detection of visual field defects is pivotal to reducing glaucoma-related vision loss. The Melbourne Rapid Fields screening module (MRF-S) is an iPad-based test, which allows suprathreshold screening with zone-based analysis to rapidly assess the risk of manifest glaucoma. The versatility of MRF-S has potential utility in rural areas and during infectious pandemics. This study evaluates the utility of MRF-S for detecting field defects in non-metropolitan settings.

Materials and methods

This was a prospective, multicenter, cross-sectional validation study. Two hundred and fifty-two eyes of 142 participants were recruited from rural sites through two outreach eye services in Australia. Participants were tested using MRF-S and compared with a reference standard; either Zeiss Humphrey Field Analyzer or Haag-Streit Octopus performed at the same visit. Standardized questionnaires were used to assess user acceptability. Major outcome measures were the area under the curve (AUC) for detecting mild and moderate field defects defined by the reference tests, along with corresponding performance characteristics (sensitivity, specificity).

Results

The mean test duration for MRF-S was 1.88 minutes compared with 5.92 minutes for reference tests. The AUCs for mild and moderate field defects were 0.81 [95% confidence interval (CI): 0.75–0.87] and 0.87 (95% CI: 0.83–0.92), respectively, indicating very good diagnostic accuracy. Using a risk criterion of 55%, MRF-S identified moderate field defects with a sensitivity and specificity of 88.4 and 81.0%, respectively.

Conclusion and clinical significance

The MRF-S iPad module can identify patients with mild and moderate field defects while delivering favorable user acceptability and short test duration. This has potential application within rural locations and amidst infectious pandemics.

How to cite this article

Chia MA, Trang E, Agar A, et al. Screening for Glaucomatous Visual Field Defects in Rural Australia with an iPad. J Curr Glaucoma Pract 2021;15(3):125–131.

Comparing the usefulness of a new algorithm to measure visual field using the variational Bayes linear regression in glaucoma patients, in comparison to the Swedish interactive thresholding algorithm

Background/aims

We previously reported that the visual field (VF) prediction model using the variational Bayes linear regression (VBLR) is useful for accurately predicting VF progression in glaucoma (Invest Ophthalmol Vis Sci. 2014, 2018). We constructed a VF measurement algorithm using VBLR, and the purpose of this study was to investigate its usefulness.

Method

122 eyes of 73 patients with open-angle glaucoma were included in the current study. VF measurement was performed using the currently proposed VBLR programme with AP-7700 perimetry (KOWA). VF measurements were also conducted using the Swedish interactive thresholding algorithm (SITA) standard programme with Humphrey field analyser. VF measurements were performed using the 24–2 test grid. Visual sensitivities, test–retest reproducibility and measurement duration were compared between the two algorithms.

Result

Mean mean deviation (MD) values with SITA standard were −7.9 and −8.7 dB (first and second measurements), whereas those with VBLR-VF were −8.2 and −8.0 dB, respectively. There were no significant differences across these values. The correlation coefficient of MD values between the 2 algorithms was 0.97 or 0.98. Test–retest reproducibility did not differ between the two algorithms. Mean measurement duration with SITA standard was 6 min and 02 s or 6 min and 00 s (first or second measurement), whereas a significantly shorter duration was associated with VBLR-VF (5 min and 23 s or 5 min and 30 s).

Conclusion

VBLR-VF reduced test duration while maintaining the same accuracy as the SITA-standard.

[Static automated perimetry in the diagnosis of glaucoma. Part 1: Basic principles]

Static automated perimetry is an indispensable tool in the diagnosis of glaucoma. It is used to study the differential light sensitivity of the retina in different points of the visual field. The most important is the central zone of the visual field, many perimetric programs and strategies have been developed for its examination. Using standard background brightness, we can vary sizes, location methods and the type of stimulus delivery. The proper use of standard achromatic perimetry is crucial for the correct management of glaucoma patients. This review analyzes literature on the basic principles of static perimetry in the examination of differential photosensitivity of the retina.

Continuous Light Increment Perimetry Compared to full Threshold Strategy in Glaucoma

PURPOSE

Continuous light increment perimetry (CLIP) is an improved testing strategy for automated static perimetry designed to save test time and enhance patient compliance. CLIP uses a modified ramp stimulus where stimulus intensity is continuously increased according to patient reaction time, starting from a subthreshold intensity until recognition. The test is constantly modified according to patient performance. As CLIP showed good results in normal subjects in previous studies, the authors now compared CLIP to the standard 4/2-full threshold (4/2) strategy in glaucoma patients.

METHODS

Fifty-two patients with glaucomatous visual field defects (mean sensitivities 2.9 to 18.4 dB), all with perimetric experience, were tested with CLIP (three times) and 4/2 in a randomized fashion. Tests were performed at 55 test locations within the central 30 degree visual field (24-2 area) using the Twinfield perimeter.

RESULTS

Average mean sensitivity was significantly higher for CLIP than for 4/2 (t test, p<0.0001). Absolute scotomas and extension of scotomas were comparable for both strategies, whereas CLIP found less deep relative scotomas in some cases. Mean test time was significantly shorter for CLIP (5.6 min) compared to 4/2 (8.9 min) (Wilcoxon signed rank test, p<0.0001). Patient acceptance was better for CLIP than for 4/2.

CONCLUSIONS

CLIP showed comparable results to 4/2 with excellent patient acceptance. Mean sensitivities are 1.8 dB higher than for 4/2; similar results were found previously in normal subjects. CLIP was able to save a mean 38% of test time compared to full threshold strategy with good reproducibility.

Influence of Test Strategy on Octopus Perimeter Cluster Mean Defect Values: Adaptive Bracketing Normal Strategy Versus Tendency-oriented Perimetry

BACKGROUND/PURPOSE

Using adaptive bracketing "normal" (N) strategy it has been shown that cluster trend analysis is useful for early detection of glaucomatous progression with Octopus perimetry. However, in clinical practice "tendency-oriented perimetry" (TOP) is mostly used. In TOP, responses given at neighboring points modify the threshold values, and this process does not respect cluster borders. In the current investigation, we evaluated the influence of test strategy on the cluster mean defect (cluster MD) values.

MATERIALS AND METHODS

Sixty-nine eyes with normal visual field and 63 glaucoma eyes with predominantly mild to moderate glaucomatous visual field defect underwent Octopus perimetry with N and TOP strategy on the same day. Cluster MD values and global parameters were compared between test strategies in each group.

RESULTS

In the normal group, all global parameters (P≤0.0003) and cluster MD for 6 uncorrected and 5 corrected clusters differed significantly between the strategies (P≤0.0052). In the glaucoma group, no significant difference was seen for global mean sensitivity and global MD, but square loss variance reflecting inhomogeneity was 1.0 dB lower with TOP (P<0.0001). Two uncorrected and 3 corrected clusters differed significantly (P≤0.0026) and several other clusters differed almost significantly between the strategies. The differences spread up to 1.9 dB without any systematic direction.

CONCLUSIONS

Using TOP, cluster MD determined for one cluster is statistically and clinically significantly influenced by responses given at points outside the cluster. This may also influence cluster trend analysis for glaucomatous progression. Therefore, TOP, although fast and easily performed, is not the optimal procedure for cluster and corrected cluster analyses.

Comparison of structure-function relationship between corresponding retinal nerve fibre layer thickness and Octopus visual field cluster defect values determined by normal and tendency-oriented strategies

BACKGROUND/AIMS

Previously, we found a strong structure-function relationship between Octopus visual field cluster sensitivity and corresponding sector retinal nerve fibre layer thickness (RNFLT) values, using normal strategy and 16 custom-made cluster-sector pairs. However, Octopus commercially offers 10 clusters, correction for diffuse defect (corrected clusters) and tendency-oriented perimetry (TOP) strategy. In the current investigation, we evaluated structure-function relationship for these conditions, respectively.

METHODS

Twenty-four healthy, 45 ocular hypertensive and 63 glaucoma eyes underwent Octopus perimetry (normal and TOP strategies) and RNFLT measurements on the same day. Pearson's correlation between corresponding cluster defect and sector RNFLT values was investigated.

RESULTS

Correlation between the corresponding cluster defect and sector RNFLT values was significant (p<0.0001) for all clusters, with both test strategies. The r values ranged from -0.3529 and -0.3877 to -0.5798 and -0.5893, respectively. The highest r values were found for the inferotemporal RNFLT sector superior and superior paracentral cluster pairs with both strategies. No difference in correlation was seen between the strategies (p≥0.183). For corrected clusters, significant correlation (p<0.01) was seen only for two inferotemporal and one superotemporal RNFLT sectors, with both strategies (r values: -0.2446, -0.2375; -0.3526, -0.3119; -0.2392, -0.2340, respectively).

CONCLUSIONS

Octopus normal and TOP strategies provide similar, moderate-to-strong negative correlation between the corresponding cluster defect and sector RNFLT values for all 10 manufacturer-provided clusters. For corrected clusters the relationship is poor, which suggests that by correcting for diffuse sensitivity loss some local glaucomatous defect is removed. For structure-function based clinical decisions, use of TOP is possible but use of corrected clusters is not recommended.

Psychophysical factors that have been applied to clinical perimetry

Perimetry is the most common clinical diagnostic test procedure for evaluating the status of peripheral visual function in the management of ocular and neurologic diseases. This procedure has an extended history, and its design, implementation and interpretation is dependent on many principles that have been developed through visual psychophysical studies of target size, target duration, background adaptation level, chromatic characteristics and other stimulus properties (see Greve, 1973; Johnson, 1994, chap. 17, 1996, 2008, 2010, chap. 23; Johnson & Keltner, 1998, chap. 7; Johnson & Sample, 2002, chap. 22; Johnson & Wall, 2011, chap. 35; Wall & Johnson, 2005, chap. 2 for reviews). This paper will provide a general overview of the history of perimetry, selection of stimulus parameters, development of test strategies, clinical testing conditions, new procedures and approaches to perimetry, experimental design, analysis and interpretation methods, hypothesis testing, prediction and forecasting procedures, and other related topics. It is somewhat paradoxical that although there have been major advances in all of these areas that have significantly enhanced the utility and value of this clinical diagnostic test, the fundamental methodology has remained mostly unchanged for thousands of years. It is hoped that this overview will be of assistance to investigators and clinicians who wish to use or modify this diagnostic procedure for their ongoing career activities.

Oculus-Spark perimetry compared with 3 procedures of glaucoma morphologic analysis (GDx, HRT, and OCT)

PURPOSE

To compare diagnostic capabilities and agreement between Oculus-Spark perimetry and 3 procedures of glaucoma morphologic analysis.

METHODS

A total of 102 normal eyes and 104 consecutive eyes with suspected or confirmed glaucoma (1 eye per subject) were analyzed in a prospective observational case-control study, using Spark strategy (Oculus Easyfield Perimeter), Heidelberg retinal tomograph (HRT), Zeiss laser polarimetry (GDx), and Cirrus optical coherence tomography (OCT).

RESULTS

Spark first phase lasted 37 seconds and all 4 phases 2:34 minutes. Specificities and sensitivities were as follows: Spark mean deviation (MD) first phase (95.1%, 85.6%), MD second and final phases (95.1%, 86.5%), GDx-nerve fiber indicator (95.1%, 57.4%), HRT-Reinhard Burk discriminant function (95.1%, 52.9%), HRT glaucoma probability score (95.1%, 71.2%), Cirrus OCT vertical cup/disc ratio (96.1%, 85.6%), and Cirrus OCT retinal nerve fiber layer thickness (95.1%, 68.0%). Diagnostic agreement between second and final Spark MD phases was kappa=0.92; between phase 1 Spark/MD and Cirrus OCT/vertical C/D ratio was kappa=0.78. Agreements between the 2 Cirrus OCT indices was kappa=0.69 and between the 2 HRT indices was kappa=0.559. The correlation coefficient between second and final MD and PSD was 0.99, and 0.98 between the number of scotomatous points. There was high concordance in scotoma position in both phases (kappa=0.86). The linear correlation coefficients between the morphologic indices were 0.48-0.78, and between morphologic and functional indices 0.51-0.76. Correlation coefficients comparing morphologic and functional indices were similar in the first and the last phase (p>0.05 in all cases).

CONCLUSIONS

Spark perimetry appears to show useful sensitivity and specificity, even in the first phase, and good agreement with the morphology.

Non-conventional perimetric methods in the detection of early glaucomatous functional damage

PURPOSE

To compare the ability of frequency-doubling technology (FDT), rarebit perimetry (RBP), and pulsar perimetry (PP) in detecting early glaucomatous functional damage.

METHODS

This prospective observational cross-sectional case study included 52 patients with early primary open-angle glaucoma (mean deviation -2.3+/-1.1 dB; pattern standard deviation 3.0+/-1.2 dB) and 53 healthy controls. Visual field (VF) testing included standard automated perimetry (SAP) Humphrey Field Analyzer 30-2, FDT N-30, RBP (version 4.0), and PP T30W. One eye per patient was considered. Sensitivity at fixed specificities and area under the receiver operating characteristic curve (AROC) for discriminating between healthy and glaucomatous eyes were calculated and compared.

RESULTS

The parameters associated with the largest AROC, which were not statistically different (Hanley-McNeil method, P0.42-0.71) were as follows: number of locations in the pattern deviation probability (PDP) plot with P<5% for FDT (0.93); mean hit rate for RBP (0.95); and mean defect for PP (0.94). PP test duration was significantly shorter than FDT and RBP (P<0.002).

CONCLUSIONS

FDT, PP, and RBP are useful non-conventional VF methods in detecting early glaucomatous VF defects with similar AROCs. The methods were rapid and easy, and PP took less than half the time than SAP. These non-conventional testing may prove to be useful in providing additional information in the diagnosis of glaucoma suspect with normal SAP results, in the therapeutic decision-making process of early glaucomatous patients, and in subjects unable to perform VF testing with SAP.

Stabilization and comparison of TOP and Bracketing perimetric strategies using a threshold spatial filter

BACKGROUND

To evaluate a new perimetric spatial filter that takes into account relations of dependence between regions of the glaucomatous visual field.

METHODS

51 glaucoma patients and 30 controls were examined using the Octopus 1-2-3 on four occasions using program 32; two with TOP and two with Bracketing (BRA) strategy. Each threshold was replaced by a filtered threshold, calculated as the mean of its own value and the four points best correlated with it, weighted with the correlation coefficient (r) that relates them.

RESULTS

Application of the filter had minimal effect on the absolute mean defect (MD) but reduced the square root of loss variance (sLV) by 17.6% in TOP and 28.8% in BRA, increasing the similarity between their results. Filtered TOP and BRA thresholds were more similar than those obtained in the two unfiltered BRA examinations. Filtering reduced the value of short fluctuation by 28.6% in TOP and 45.4% in BRA and reduced sLV fluctuation by 14.3% in TOP and 24.2% in BRA, thus harmonizing the two strategies for these two parameters (p > 0.05). The influence of filtering on MD fluctuation was minimal (p > 0.05). In normal subjects the number of points beyond 5 dB of normality (not reproducible false scotomas) reduced from 1.5% to 0.2% in TOP and from 4.9% to 1.6% in BRA, while in glaucoma patients changes were minimal.

CONCLUSIONS

The proposed spatial filter stabilized perimetric results, acting with greater effect on BRA than on TOP, making their results more similar.

Optic Disc Tomography and Perimetry in Controls, Glaucoma Suspects, and Early and Established Glaucomas

PURPOSE

To analyze the priority of morphological and functional defects in glaucoma.

METHODS

Nine-hundred seventy-three eyes of 973 subjects were examined with Heidelberg retinal tomograph (HRT II) and Octopus 311 perimeter (TOP strategy). These included 72 controls (C), 659 early and suspect open angle glaucoma (ESG) with perimetric mean defect (MD) lower than 6 dB, and 242 confirmed moderate and advanced glaucomas (AG) with perimetric MD>or=6 dB.

RESULTS

I. (Control group): Age was significantly correlated with mean sensitivity (MS) (r=0.50, p<0.00001) and nasal cup shape measure (r=0.33, p=0.005). II. (C and ESG groups): For 95.8% specificity, the best sensitivity was obtained with square root of loss variance (sLV) (ROC area=69.7%, sensitivity=33.7%) and maximum contour elevation (ROC area=69.6%, sensitivity=29.0%). Maximum contour elevation and sLV coincided in diagnosis in 12.4% of cases. An equation using 64 HRT II indices predicted MS with a standard error of estimate (SEE) of 1.87 dB (r=0.67, p<0.00001) and MD (SEE=1.88 dB, r=0.47, p<0.00001). III. (All cases): RB discriminant function value was the best HRT II index to estimate MS values (SEE=5.4 dB, r=0.52, p<0.0001), MD (SEE=5.2 dB, r=0.50, p<0.0001), sLV (SEE=1.9 dB, r=0.41, p<0.0001) and Number of Pathological Points (NPP; SEE=21.3 dB, r=0.49, p<0.0001). Sector correlation of the optic nerve and visual field was high (maximum r=0.66) in cases with superior visual field defects and low in the rest of cases. More than 95% of cases with established glaucoma had abnormal sLV, but <60% had abnormal optic disc indices.

DISCUSSION

Perimetry reveals age-related defects slightly more than HRT II. HRT II indices correlated better with MS than with MD, probably because none of them was age corrected. Good correlation between anatomical and functional data in C and ESG, and sensitivity results indicated small differences in early development between both methods. Perimetry identifies defects more clearly than structural measures in established glaucoma.

Diagnostic accuracy and reproducibility of tendency oriented perimetry in glaucoma

PURPOSE

To evaluate the diagnostic capability of tendency oriented perimetry (TOP) in glaucoma.

METHODS

A): The diagnostic accuracy of mean defect (MD), square-root of the loss variance (s LV), and number of pathologic points (NPP) was calculated in 295 normal and 414 glaucoma eyes (179 early, 112 moderate, and 123 advanced) examined with TOP. B): Threshold fluctuation (F) and its relationship with the loss variance (LV) was measured in 34 normal and 33 glaucoma eyes (mean MD=3 dB; SD=3.9) for TOP and for full-threshold perimetry (FT). C): Twenty-eight eyes with stable glaucoma (mean MD=9.5 dB; SD=7.2) were examined six times to quantify LV error. D): TOP and FT were tested with the simulation program PeriSim using different behavior models.

RESULTS

A): The best diagnostic index in early glaucoma (MD<6dB) was sLV (specificity=90.2%, sensitivity=84.9). The three indices had similar precision in moderate and severe glaucoma. B): Threshold fluctuation and sLV were better correlated in TOP (r=0.72, p<0.01) than in FT (r=0.62, p<0.01). For normal subjects, in FT the incidence of F<2 dB was 8.82% and s LV<1.5 dB 5.88%. The same frequencies in TOP were 67.65% and 55.88%. C): Averaging six examinations reduced the sLV val ue by 22%. D): The threshold estimation error increased 1 dB in TOP in relation to FT for the same patient's behavior, but the error in TOP was lower than i n FT when the worst behavior was modeled.

CONCLUSIONS

TOP is a good discriminator between glaucoma and normality. Perimetry results overestimate the real sLV value. TOP's high diagnostic ability is probably associated to the algorithm design and to less contaminating influences during the examination.

Comparison of Diagnostic Ability between a Fast Strategy, Tendency-Oriented Perimetry, and the Standard Bracketing Strategy

PURPOSE

To compare the diagnostic abilities of the standard bracketing strategy (BR) and a fast strategy, the tendency-oriented perimetry (TOP).

METHODS

Seventy-seven controls and 91 eyes from patients with glaucoma were analyzed with the strategies TOP and BR. Sensitivity (Se), specificity (Sp), the area under the receiver operating characteristic (ROC) curve (AC) and the optimum cutoff value (CO) were calculated for the visual field indices mean defect (MD), the square root of the loss variance (sLV) and the number of pathological points (NPP).

RESULTS

In the glaucoma group, the mean MD value using TOP and BR was 7.5 and 8.3 dB, respectively. The mean sLV value using TOP and BR was 5.0 and 5.3 dB, respectively. Indices provided by TOP had higher ROC values than the ones provided by BR. Using TOP, the index with the best diagnostic ability was sLV (Sp = 94.8, Se = 90.1, AC = 0.966, CO = 2.5 dB), followed by NPP and MD. Using BR, the best results were obtained for MD (Sp = 92.2, Se = 81.3, AC = 0.900, CO = 2.5 dB) followed by sLV and NPP.

CONCLUSIONS

A fast strategy, TOP, had superior diagnostic ability than the standard BR. Although TOP provided lower LV values than BR, the diagnostic ability of this index was higher than that of the conventional strategy.

The Finnish evidence-based guideline for open-angle glaucoma

In most patients, chronic open-angle glaucoma is a slowly progressive disease. Eyes with very high intraocular pressure (IOP > 30 mmHg) represent an exception to this and should be treated and followed extremely intensively. As lowering IOP is, so far, the only means of treating glaucoma, the majority of research reports deal with the IOP-lowering effect of the treatment. The primary goal of treatment, however, is to prevent glaucomatous damage to the structures and function of the eye. The effectiveness of treatment is monitored with optic disc and retinal nerve fibre layer imaging and with visual field examinations. If the glaucomatous changes are progressing, more effective treatment should be given. In the course of follow-up, it should be noted that the changes in the optic nerve structure and function appear and progress at different time-points with delays of up to several years. The assessment of abnormalities is dependent on the examination method and requires a great deal of experience on the part of the examiner. The important risk factors in glaucoma are elevated IOP (even if IOP is within normal range in half of patients ), age, positive family history, exfoliation, race and myopia.

Multicenter evaluation of tendency-oriented perimetry (TOP) using the G1 grid

PURPOSE

The G1-TOP program is a short automated perimetric strategy which sub-divides the G1 grid of 59 points into four sub-grids. Each point is tested only once, but each patient's response is used to modify that particular point and the surrounding ones from the remaining sub-grids. This study compared the results of the G1-TOP program with the Standard Bracketing strategy.

METHODS

Eleven participating institutions provided data from 213 patients (406 eyes). The main group consisted of 284 glaucomas and 55 glaucoma suspects. Other groups included 31 eyes with neurological disorders, 20 with chorioretinal lesions and 16 normal eyes. Mean age was 62.7 +/- 15.4 (range 14-88) years. All subjects had previous perimetric experience and visual acuity better than 0.5. Examination included G1-Standard Bracketing and G1-TOP testing, in interchangeable order, with the Octopus 1-2-3 perimeter.

RESULTS

The correlation coefficient for mean defect (MD) was 0.95. Standard error (YX) for MD, square root of loss variance (LV) and individual thresholds were 1.86 dB, 1.29 dB, and 4.72 dB, respectively. Mean sensitivity values were similar (difference 0.04 +/- 1.87 dB) (p>0.05). Mean duration for G1-TOP was 2.19 +/- 0.26 min, while G1-Standard Bracketing took 11.51 +/- 1.52 min (ratio 1/5.1, or a net reduction of 80.4%). The sensitivity of G1-TOP versus G1-Standard Bracketing was: glaucoma 77.1/78.5, glaucoma suspects 38.2/47.3, neurological disorders 87.1/87.1 and chorioretinal lesions 80.0/85.0.

CONCLUSIONS

The G1-TOP program gave very similar results to G1-Standard Bracketing in only 20% of the time required by the standard strategy.