Visual field test simulation and error in threshold estimation.

Spenceley, S.E.; Henson, David B.

doi:10.1136/bjo.80.4.304

Cited by 25 publications

(19 citation statements)

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“…[13][14][15][16] The virtual eye simulation described in this study may be useful for exploring the behaviour of visual field progression. Previously we have used a computer simulation similar to the one described here to show that PLR is equally sensitive to detecting both gradual (linear) and sudden (episodic) sensitivity loss.…”

Section: Discussionmentioning

confidence: 99%

“…This type of investigation, like others examining methods for quantifying visual field changes, is hampered by the lack of an external "gold standard" for progression. Computer simulations have been extensively used as an alternative to analysing actual patient data to develop improved perimetric testing strategies [13][14][15][16] : they offer a more reproducible and controllable means of examining the behaviour of visual field data. This suggests that they may also be useful in examining the problems of detecting progression in series of visual field data.…”

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confidence: 99%

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Frequency of testing for detecting visual field progression

Gardiner

Crabb

2002

British Journal of Ophthalmology

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Aims: To investigate the effect of frequency of testing on the determination of visual field progression using pointwise linear regression (PLR). Methods: A "virtual eye" was developed to simulate series of sensitivities over time at a given point in the eye. The user can input the actual behaviour of the point (for example, stable or deteriorating steadily), and then a configurable amount of noise is added to produce a realistic series over time. The advantage of this over using patient data is that the actual status of the eye is known. Series were generated using different frequencies of testing, and the diagnosis that would have been made from each series was compared with the true status of the eye. A point was diagnosed as progressing if the regression line for the series showed a deterioration of at least 1 dB per year, significant at the 1% level. From these results, graphs were produced showing the number of points correctly or incorrectly diagnosed as progressing. Results: With the virtual eye deteriorating at a rate of 2 dB/year, it was found that the point was determined to be progressing quicker when more tests were carried out each year. With a stable virtual eye, it was found that increasing the frequency of testing increased the number of series that were falsely labelled as progressing during the first 3 years of testing. Conclusions: As the frequency of testing increases, the sensitivity of PLR increases. However, the specificity decreases; possibly meaning more unnecessary changes in treatment. Three tests per year provide a good compromise between sensitivity and specificity. V isual field results from computerised perimetry are the standard measurement of a patient's visual function and are likely to remain so in future years, especially with the promise of better measurement strategies.1 2 Perimetry shows the actual effect on the patient's vision, which will vary even among patients with, for example, the same degree of inflated intraocular pressure or damage to the optic nerve. Evaluation of change in a series of visual fields remains an important aspect of monitoring patients for disease progression. New methods, using linear regression analysis of individual sensitivity values against time of follow up have been developed. [3][4][5][6] These techniques, known as pointwise linear regression (PLR), have been shown by several studies to compare favourably with other methods for detecting visual field progression in patients with glaucoma. 7-12The main purpose of this study was to investigate the effect of frequency of testing on the performance of PLR in detecting gradual sensitivity deterioration. This is particularly important to the clinical management of patients with glaucoma. This type of investigation, like others examining methods for quantifying visual field changes, is hampered by the lack of an external "gold standard" for progression. Computer simulations have been extensively used as an alternative to analysing actual patient data to develop improved perimetric testing strategi...

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Frequency of testing for detecting visual field progression

Gardiner

Crabb

2002

British Journal of Ophthalmology

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“…To counteract this effect, we calculated a correction based on the tested normal subjects and applied this correction to all subjects. Knowing about the flattening of the FOS curve with increased defect depth [23] we would expect that a correction based on normal threshold levels would not completely correct the deviation in areas with defects. However, in our study we could not observe the defects being shallower on average, compared to the NS strategy; a fact, we did not find an explanation for.…”

Section: Discussionmentioning

confidence: 99%

A Comparison between the Pulsed Rising Amplitude Perimetry and the Normal Staircase Strategy in Standard Automated Perimetry

Todorova¹,

Palmowski-Wolfe²

2013

J Clin Exp Ophthalmol

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IntroductionStandard automated perimetry (SAP) is the currently accepted gold standard for detection and monitoring of glaucomatous dysfunction [1]. The outcome of SAP as a psychophysical test, however, is subjective and variable [2,3]. In the normal strategy (NS) the stimulus luminance varies stepwise, in order to define thresholds. As published literature clearly demonstrates, in cases with advanced visual field disturbances, increasing the accuracy of the estimated threshold and its reproducibility require prolongation of the examination time. This, in consequence, results in increasing fatigue-related artefacts [2,3], which hinder a direct comparison of local threshold resolution.New fast perimetric strategies, like Dynamic, Swedish Interactive Threshold Algorithm (SITA) and Tendency-Oriented Perimetry (TOP) aim at achieving a comparable high sensitivity and specificity for detection of disease and progression analysis, while taking considerably less time. Here, the examination time is decreased using the prior information about age-corrected normal thresholds values, frequency-of-seeing curves (FOS-curves) and correlations between different points, while the results of the already tested neighbouring points are taken into account, as well [4][5][6][7][8][9]. The significant gain in time in the TOP strategy, however, is producing a reduction in spatial resolution, making the test unsuitable for application in pathologies with very narrow, deep defects [8,9].One further attempt in optimising the test duration, while keeping an accurate threshold determination, is the introduction of methods based on continuous luminance variation. The rising amplitude perimetry (RAMP) and its modification -the continuous light increment strategy (CLIP) [10,11], in contrast to the TOP strategy, is assessing every single test location independently. Here, the slow temporal onset algorithm starts from invisible (subthreshold) light and increases in luminance until the patient responds to the light.In general, the determination of thresholds varies complexly and is dependent on several variables, including the effect of temporal summation, stimulus duration, speed of the light onset and wavelength of monochromatic light [12,13].For CLIP methods, the summative phenomenon of the neighboring areas after exposure to light, that is the effect of temporal summation, AbstractBackground and scope: Pulsed rising amplitude perimetry (pulsed RAMP) is an improved strategy for automated static perimetry, developed to save examination time without accuracy loss. The aim of this study was to identify characteristic differences between the normal strategy (NS) and the pulsed RAMP strategy in standard automated perimetry, in order to evaluate the potential of the pulsed RAMP for threshold estimation.

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“…Although there are typical visual field defects that occur with patterns of structural losses in disease, that is, structure‐function concordance, results in reality are often confounded by inherent variability of the measurement technique . This is especially true for diseases with slow progression or in the early stages of disease .…”

Section: The Problem Of Structure‐function Discordancementioning

confidence: 99%

The value of visual field testing in the era of advanced imaging: clinical and psychophysical perspectives

Phu

Khuu

Yapp

et al. 2017

Clinical and Experimental Optometry

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White‐on‐white standard automated perimetry (SAP) is widely used in clinical and research settings for assessment of contrast sensitivity using incremental light stimuli across the visual field. It is one of the main functional measures of the effect of disease upon the visual system. SAP has evolved over the last 40 years to become an indispensable tool for comprehensive assessment of visual function. In modern clinical practice, a range of objective measurements of ocular structure, such as optical coherence tomography, have also become invaluable additions to the arsenal of the ophthalmic examination. Although structure‐function correlation is a highly desirable determinant of an unambiguous clinical picture for a patient, in practice, clinicians are often faced with discordance of structural and functional results, which presents them with a challenge. The construction principles behind the development of SAP are used to discuss the interpretation of visual fields, as well as the problem of structure‐function discordance. Through illustrative clinical examples, we provide useful insights to assist clinicians in combining a range of clinical results obtained from SAP and from advanced imaging techniques into a coherent picture that can help direct clinical management.

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Visual field test simulation and error in threshold estimation.

Cited by 25 publications

References 10 publications

Frequency of testing for detecting visual field progression

Frequency of testing for detecting visual field progression

A Comparison between the Pulsed Rising Amplitude Perimetry and the Normal Staircase Strategy in Standard Automated Perimetry

The value of visual field testing in the era of advanced imaging: clinical and psychophysical perspectives

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