Chancellery Research - Research Publications

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    Developing a Screening Tool for Areas of Abnormal Central Vision Using Visual Stimuli With Natural Scene Statistics
    Srinivasan, R ; Turpin, A ; McKendrick, AM (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2022-02-01)
    PURPOSE: Previous studies show that some visual field (VF) defects are detectable from visual search behavior; for example, when watching video. Here, we developed and tested a VF testing approach that measures the number of fixations to find targets on a background with spatial frequency content similar to natural scenes. METHODS: Twenty-one older controls and 20 people with glaucoma participated. Participants searched for a Gabor (6 c/°) that appeared in one of 25 possible locations within a 15° (visual angle) 1/f noise background (RMS contrast: 0.20). Procedure performance was assessed by calculating sensitivity and specificity for different combinations of control performance limits (p = 95%, 98%, 99%), number of target locations with fixations outside control performance limits (k = 0 to 25) and number of repeated target presentations (n = 1 to 20). RESULTS: Controls made a median of two to three fixations (twenty-fifth to seventy-fifth percentile: two to four) to locate the target depending on location. A VF was flagged "abnormal" when the number of fixations was greater than the p = 99% for k = 3 or more locations with n = 2 repeated presentations, giving 85% sensitivity and 95.2% specificity. The median test time for controls was 85.71 (twenty-fifth to seventy-fifth percentile: 66.49-113.53) seconds. CONCLUSION: Our prototype test demonstrated effective and efficient screening of abnormal areas in central vision. TRANSLATIONAL RELEVANCE: Visual search behavior can be used to detect central vision loss and may produce results that relate well to performance in natural visual environments.
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    Do Additional Testing Locations Improve the Detection of Macular Perimetric Defects in Glaucoma?
    Montesano, G ; McKendrick, AM ; Turpin, A ; Brusini, P ; Oddone, F ; Fogagnolo, P ; Perdicchi, A ; Johnson, CA ; Lanzetta, P ; Rossetti, LM ; Garway-Heath, DF ; Crabb, DP (ELSEVIER SCIENCE INC, 2021-11-18)
    PURPOSE: To evaluate the ability of additional central testing locations to improve detection of macular visual field (VF) defects in glaucoma. DESIGN: Prospective cross-sectional study. PARTICIPANTS: Four hundred forty healthy people and 499 patients with glaucomatous optic neuropathy (GON) were tested with a fundus tracked perimeter (CMP; CenterVue) using a 24-2 grid with 12 additional macular locations (24-2+). METHODS: Glaucomatous optic neuropathy was identified based on expert evaluation of optic nerve head photographs and OCT scans, independently of the VF. We defined macular defects as locations with measurements outside the 5% and 2% normative limits on total deviation (TD) and pattern deviation (PD) maps within the VF central 10°. Classification was based on the total number of affected macular locations (overall detection) or the largest number of affected macular locations connected in a contiguous cluster (cluster detection). Criteria based on the number of locations and cluster size were used to obtain equivalent specificity between the 24-2 grid and the 24-2+ grids, calculated using false detections in the healthy cohort. Partial areas under the receiver operating characteristic curve (pAUCs) were also compared at specificities of 95% or more. MAIN OUTCOME MEASURES: Matched specificity comparison of the ability to detect glaucomatous macular defects between the 24-2 and 24-2+ grids. RESULTS: At matched specificity, cluster detection identified more macular defects with the 24-2+ grid compared with the 24-2 grid. For example, the mean increase in percentage of detection was 8% (95% confidence interval [CI], 5%-11%) and 10% (95% CI, 7%-13%) for 5% TD and PD maps, respectively, and 5% (95% CI, 2%-7%) and 6% (95% CI, 4%-8%) for the 2% TD and PD maps, respectively. Good agreement was found between the 2 grids. The improvement measured by pAUCs was also significant but generally small. The percentage of eyes with macular defects ranged from about 30% to 50%. Test time for the 24-2+ grid was longer (21% increase) for both cohorts. Between 74% and 98% of defects missed by the 24-2 grid had at least 1 location with sensitivity of < 20 dB. CONCLUSIONS: Visual field examinations with additional macular locations can improve the detection of macular defects in GON modestly without loss of specificity when appropriate criteria are selected.
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    Subjective measurement of the Stiles-Crawford effect with different field sizes
    Nilagiri, VK ; Suheimat, M ; Lambert, AJ ; Turpin, A ; Vohnsen, B ; Atchison, DA (OPTICAL SOC AMER, 2021-08-01)
    The Stiles-Crawford effect of the first kind (SCE) is the phenomenon in which light entering the eye near the center of the pupil appears brighter than light entering near the edge. Previous investigations have found an increase in the directionality (steepness) of the effect as the testing location moves from the center of the visual field to parafoveal positions, but the effect of central field size has not been considered. The influence of field size on the SCE was investigated using a uniaxial Maxwellian system in which stimulus presentation was controlled by an active-matrix liquid crystal display. SCE directionality increased as field size increased from 0.5° to 4.7° diameter, although this was noted in four mild myopes and not in two emmetropes. The change with field size was supported by a geometric optics absorption model.
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    ConTEXT Explorer: a web-based text analysis tool for exploring and visualizing concepts across time
    Yang, Z ; Mikolajczak, G ; Turpin, A (The Open Journal, 2021-12-09)
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    A Method for Reducing the Number of Presentations in Perimetric Test Procedures.
    Turpin, A ; McKendrick, AM (Association for Research in Vision and Ophthalmology (ARVO), 2022-04-01)
    Purpose: To introduce a new method (ARBON) for decreasing the test time of psychophysical procedures and examine its application to perimetry. Methods: ARBON runs in parallel with an existing psychophysical procedure injecting occasional responses of seen or unseen into that procedure. Using computer simulation to mimic human responses during perimetry, we assess the performance of ARBON relative to an underlying test procedure and a version of that procedure truncated to be faster. Simulations used 610 normal eyes (age 20 to 80 years) and 163 glaucoma eyes (median mean deviation = -1.81 dB, 5th percentile = +2.14 dB, 95th percentile = -22.55 dB). Outcome measures were number of presentations and mean absolute error in threshold estimation. We also examined the probability distribution of measured thresholds. Results: ARBON and the Truncated procedure reduced presentations by 16% and 18%, respectively. Mean error was increased by 8% to 10% for the Truncated procedure but decreased by 5% to 7% for ARBON. The probability distributions of measured thresholds using ARBON overlapped with the Underlying procedure by over 80%, whereas the Truncated procedure overlapped by 50%. Conclusions: ARBON offers a principled method for reducing test time. ARBON can be added to any existing psychophysical procedure without requiring any change to the logic or parameters controlling the procedure, resulting in distributions of measured thresholds similar to those of the underlying procedure. Translational Relevance: ARBON can be added to a perimetry test procedure to speed up the test while largely preserving the distribution of returned sensitivities, thus producing normative data similar to the data for the original, underlying perimetric test.
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    The Open Perimetry Initiative: A framework for cross-platform development for the new generation of portable perimeters
    Marin-Franch, I ; Turpin, A ; Artes, PH ; Chong, LX ; McKendrick, AM ; Alawa, KA ; Wall, M (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2022-04-01)
    The Open Perimetry Initiative was formed in 2010 with the aim of reducing barriers to clinical research with visual fields and perimetry. Our two principal tools are the Open Perimetry Interface (OPI) and the visualFields package with analytical tools. Both are fully open source. The OPI package contains a growing number of drivers for commercially available perimeters, head-mounted devices, and virtual reality headsets. The visualFields package contains tools for the analysis and visualization of visual field data, including methods to compute deviation values and probability maps. We introduce a new frontend, the opiApp, that provides tools for customization for visual field testing and can be used as a frontend to run the OPI. The app can be used on the Octopus 900 (Haag-Streit), the Compass (iCare), the AP 7000 (Kowa), and the IMO (CREWT) perimeters, with permission from the device manufacturers. The app can also be used on Android phones with virtual reality headsets via a new driver interface, the PhoneHMD, implemented on the OPI. The use of the tools provided by the OPI library is showcased with a custom static automated perimetry test for the full visual field (up to 50 degrees nasally and 80 degrees temporally) developed with the OPI driver for the Octopus 900 and using visualFields for statistical analysis. With more than 60 citations in clinical and translational science journals, this initiative has contributed significantly to expand research in perimetry. The continued support of researchers, clinicians, and industry are key in transforming perimetry research into an open science.
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    Increased Depth, Reduced Extent, and Sharpened Edges of Visual Field Defects Measured by Compass Fundus Perimeter Compared to Humphrey Field Analyzer
    Liu, P ; Nguyen, BN ; Turpin, A ; McKendrick, AM (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2021-10-01)
    Purpose: The purpose of this study was to compare visual field results of the COMPASS fundus perimeter (CMP) and the Humphrey Field Analyzer (HFA) in the same eyes; to compare structure-function concordance between circumpapillary retinal nerve fiber layer (Cp-RNFL) profiles and the two perimetry results; and to evaluate whether differences between the two results reflect postulated advantages of real-time eye movement compensation during perimetry. Methods: We retrospectively analyzed 24-2 visual field data measured with CMP and HFA together with Cp-RNFL optical coherence tomography (OCT) scan data from 95 eyes of 65 people with glaucoma. We defined visual field locations with total deviation (TD) less than -5 dB as defective. The CMP and HFA fields were compared on measures of: spatial extent (number of defective locations); depth (TD values); and sharpness of scotomata edges (maximum TD difference between defective locations and their neighbors). Structure-function concordance between Cp-RNFL profile and respective visual field was also compared. Results: Compared to the HFA, scotomata measured by CMP were of reduced spatial extent (mean difference = -3.14 locations, p < 0.001), greater depth (median TD of CMP = -17 dB versus HFA = -13 dB, p = 0.029) and steeper edges (median of maximum TD difference of CMP = 10.6 dB versus HFA = 6 dB, p < 0.001). Structure-function concordance between Cp-RNFL profile and either visual field were comparable despite the reduced scotoma spatial extent measured by CMP. Conclusions: Glaucomatous visual fields measured by CMP displayed characteristics consistent with expected effects of using real-time eye movement compensation technology compared to the widely used HFA. Translational Relevance: Glaucomatous visual field defects measured by the CMP are more localized, deeper, and steeper than those of the HFA.
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    Visual Field Progression in Glaucoma: Comparison Between PoPLR and ANSWERS
    Marin-Franch, I ; Artes, PH ; Turpin, A ; Racette, L (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2021-12-01)
    Purpose: It has been suggested that the detection of visual field progression can be improved by modeling statistical properties of the data such as the increasing retest variability and the spatial correlation among visual field locations. We compared a method that models those properties, Analysis with Non-Stationary Weibull Error Regression and Spatial Enhancement (ANSWERS), against a simpler one that does not, Permutation of Pointwise Linear Regression (PoPLR). Methods: Visual field series from three independent longitudinal studies in patients with glaucoma were used to compare the positive rate of PoPLR and ANSWERS. To estimate the false-positive rate, the same visual field series were randomly re-ordered in time. The first dataset consisted of series of 7 visual fields from 101 eyes, the second consisted of series of 9 visual fields from 150 eyes, and the third consisted of series of more than 9 visual fields (17.5 on average) from 139 eyes. Results: For a statistical significance of 0.05, the false-positive rates for ANSWERS were about 3 times greater than expected at 15%, 17%, and 16%, respectively, whereas for PoPLR they were 7%, 3%, and 6%. After equating the specificities at 0.05 for both models, positive rates for ANSWERS were 16%, 25%, and 38%, whereas for PoPLR they were 12%, 33%, and 49%, or about 5% greater on average (95% confidence interval = -1% to 11%). Conclusions: Despite being simpler and less computationally demanding, PoPLR was at least as sensitive to deterioration as ANSWERS once the specificities were equated. Translational Relevance: Close control of false-positive rates is key when visual fields of patients are analyzed for change in both clinical practice and clinical trials.
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    Principles of Melbourne Connect
    Gruba, P ; Turpin, A ( 2021)
    Melbourne Connect is a new initiative partnership between The University of Melbourne and industry groups. It is the centrepiece of a new innovation ecosystem connected to the university. In this paper we outlined the motivation and methods used to define a set of underlying principles for the operation of the innovation ecosystem.
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    Developing a workforce to support research reliant on data and compute
    Turpin, A ; Gruba, P ; Pozanenko, A ; Stupnikov, S ; Thalheim, B ; Mendez, E ; Kiselyova, N (CEUR, 2021-01-01)
    We describe the construction, operation and evaluation of the Melbourne Data Analytics Platform; a group of academics whose mission is to support research requiring non-trivial data analysis or compute at the University of Melbourne.