The Effect of Stimulus Size on the Reliable Stimulus Range of Perimetry

Gardiner, Stuart K.; Demirel, Shaban; Goren, Deborah; Mansberger, Steven L.; Swanson, William H.

doi:10.1167/tvst.4.2.10

Cited by 42 publications

(62 citation statements)

References 34 publications

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“…2B), which may be accredited to the greater number of response elements recruited with a larger stimulus size compensating for the reduced density. 28 This is also consistent with the results of a previous study, 51 which suggests better response characteristic can be attained in areas with sensitivity below the measurement floor with a larger stimulus size. Therefore, selection of a stimulus size within the spatial summation area but not smaller than truly necessary may maximize the signal-to-noise ratio.…”

Section: Practical Implications Of Structure-function Correlation Witsupporting

confidence: 91%

Consistency of Structure-Function Correlation Between Spatially Scaled Visual Field Stimuli and In Vivo OCT Ganglion Cell Counts

Yoshioka

Zangerl

Phu

et al. 2018

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. To investigate the effect of stimulus size and disease status on the structure-function relationship within the central retina, we correlated the differential light sensitivity (DLS) with Goldmann stimulus size I to V (GI-V) and optical coherence tomography (OCT) derived in vivo ganglion cell count per stimulus area (GCc) within the macular area in normal subjects and patients with early glaucoma.METHODS. Humphrey Field Analyzer 10-2 visual field data with GI through V and Spectralis OCT macular ganglion cell layer (GCL) thickness measurements were collected from normal and early glaucoma cohorts including 25 subjects each. GCc was calculated from GCL thickness data and correlated with DLSs for different stimulus sizes.RESULTS. Correlation coefficients attained with smaller stimulus size were higher compared to larger stimulus sizes in both normal (GI-GII: R 2 ¼ 0.41-0.43, GIII-GV: R 2 ¼ 0.16-0.41) and diseased cohorts (GI-GII: R 2 ¼ 0.33-0.41, GIII-GV: R 2 ¼ 0.19-0.36). Quadratic regression curves for combined GI to V data demonstrated high correlation (R 2 = 0.82-0.90) and differed less than 1 dB of visual sensitivity within the GCc range between cohorts. The established structure-function relationship was compatible with a histologically derived model correlation spanning the range predicted by stimulus sizes GI to GIII.CONCLUSIONS. Stimulus sizes within critical spatial summation area (GI-II) improved structurefunction correlations in the central visual field. The structure-function relationship was identical in both normal and diseased cohort when GI to GV data were combined. Congruency of GI and GII structure-function correlation with those previously derived with GIII from more peripheral locations further suggests that the structure-function relationship is governed by the number of ganglion cell per stimulus area.

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Section: Practical Implications Of Structure-function Correlation Witsupporting

confidence: 91%

Consistency of Structure-Function Correlation Between Spatially Scaled Visual Field Stimuli and In Vivo OCT Ganglion Cell Counts

Yoshioka

Zangerl

Phu

et al. 2018

Invest. Ophthalmol. Vis. Sci.

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“…In another study the investigators found no evidence that use of a size V stimulus significantly decreased the lower limit of the reliable stimulus range beyond 15–19 dB (Gardiner et al, 2015); however, using a size V stimulus resulted in a higher sensitivity at the same location. For instance, a test location that reached a sensitivity value of 15 dB with size III may reveal a sensitivity of 20 dB when tested with a size V stimulus.…”

Section: Detection Of Visual Field Progressionmentioning

confidence: 99%

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

Moraes

Liebmann

Levin

2017

Progress in Retinal and Eye Research

149

123

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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.

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“…Using Size V (1.72° diameter) stimuli instead of the more conventional Size III (0.43° diameter) stimuli reduces variability at any given location, 15 but this appears to be driven solely by the increase in sensitivity caused by use of larger stimuli, 16 implying that it postpones but does not prevent the point at which variability is too high to be able to distinguish true change from noise in a clinic situation. It may be more efficient to present larger stimuli if the test subject does not respond to a 15-dB Size III stimulus, as is done by the Heidelberg Edge Perimeter (Heidelberg Engineering, Heidelberg, Germany).…”

Section: Discussionmentioning

confidence: 99%

“…Another possibility would be to use larger stimuli throughout the range to reduce variability 15 and extend the range of severities over which reliable measurements could be obtained. 16,17 Size threshold perimetry, whereby stimulus size is altered rather than contrast, may also extend the dynamic range without increasing variability, 18 although this would require more extensive modifications to clinical perimeters so as to meet the need for a sufficient number of different stimulus sizes.…”

Section: Discussionmentioning

confidence: 99%

Effect of Restricting Perimetry Testing Algorithms to Reliable Sensitivities on Test-Retest Variability

Gardiner

Mansberger

2016

Invest. Ophthalmol. Vis. Sci.

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PurposeWe have previously shown that sensitivities obtained at severely damaged visual field locations (<15–19 dB) are unreliable and highly variable. This study evaluates a testing algorithm that does not present very high contrast stimuli in damaged locations above approximately 1000% contrast, but instead concentrates on more precise estimation at remaining locations.MethodsA trained ophthalmic technician tested 36 eyes of 36 participants twice with each of two different testing algorithms: ZEST0, which allowed sensitivities within the range 0 to 35 dB, and ZEST15, which allowed sensitivities between 15 and 35 dB but was otherwise identical. The difference between the two runs for the same algorithm was used as a measure of test-retest variability. These were compared between algorithms using a random effects model with homoscedastic within-group errors whose variance was allowed to differ between algorithms.ResultsThe estimated test-retest variance for ZEST15 was 53.1% of the test-retest variance for ZEST0, with 95% confidence interval (50.5%–55.7%). Among locations whose sensitivity was ≥17 dB on all tests, the variability of ZEST15 was 86.4% of the test-retest variance for ZEST0, with 95% confidence interval (79.3%–94.0%).ConclusionsRestricting the range of possible sensitivity estimates reduced test-retest variability, not only at locations with severe damage but also at locations with higher sensitivity. Future visual field algorithms should avoid high-contrast stimuli in severely damaged locations. Given that low sensitivities cannot be measured reliably enough for most clinical uses, it appears to be more efficient to concentrate on more precise testing of less damaged locations.

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The Effect of Stimulus Size on the Reliable Stimulus Range of Perimetry

Cited by 42 publications

References 34 publications

Consistency of Structure-Function Correlation Between Spatially Scaled Visual Field Stimuli and In Vivo OCT Ganglion Cell Counts

Consistency of Structure-Function Correlation Between Spatially Scaled Visual Field Stimuli and In Vivo OCT Ganglion Cell Counts

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

Effect of Restricting Perimetry Testing Algorithms to Reliable Sensitivities on Test-Retest Variability

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