Publications by authors named "Jack Phu"

41 Publications

Adaptations of early career optometrists in clinical practice during the COVID-19 pandemic.

Clin Exp Optom 2021 May 20:1-6. Epub 2021 May 20.

Private Practice, Sydney, New South Wales, Australia.

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http://dx.doi.org/10.1080/08164622.2021.1924628DOI Listing
May 2021

Viability of performing multiple 24-2 visual field examinations at the same clinical visit: the Frontloading Fields Study (FFS).

Am J Ophthalmol 2021 May 2. Epub 2021 May 2.

Centre for Eye Health, University of New South Wales, Kensington, NSW; School of Optometry and Vision Science, University of New South Wales, Kensington, NSW.

Purpose: To assess the viability in terms of time taken for testing and repeatability of frontloading (performing multiple perimetric examinations) in a single clinic visit.

Design: Reliability enhancement analysis.

Participants: 329 healthy, glaucoma suspect, and glaucoma subjects within a glaucoma clinic undergoing perimetric testing using SITA-Faster twice for each eye within the same session. We analysed global indices, pointwise sensitivity and probability scores, test duration and reliability metrics.

Results: 9.1% of right and 6.7% of left eye results were unreliable for both tests, with 58.4% and 67.5% of right and left eyes achieving reliable results on both. 83.8% of all subjects spent less than 20 minutes performing all tests. Differences in global indices, pointwise sensitivity and probability scores showed no systematic nor clinically significant difference between test one and two for each eye. There was also no systematic difference in the number of test locations identified as defective at the p < 0.05 level between tests. Test results that were unreliable tended to show more instances of a failed "cluster" criterion that were not repeatable.

Conclusions: Frontloading using SITA-Faster was viable for obtaining sets of reliable, repeatable perimetric data in terms of conventional outputs, overcoming practical issues regarding low test reliability using singleton results and confirmation of visual field defects. Despite the need to remain cognisant of the reliability of SITA-Faster, frontloading using this algorithm may be a practical method for meeting recommendations for multiple perimetric data required to make confident inferences about glaucoma state and progression.
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http://dx.doi.org/10.1016/j.ajo.2021.04.019DOI Listing
May 2021

Comparison of 10-2 and 24-2C Test Grids for Identifying Central Visual Field Defects in Glaucoma and Suspect Patients.

Ophthalmology 2021 Mar 17. Epub 2021 Mar 17.

Centre for Eye Health, University of New South Wales, Kensington, New South Wales; School of Optometry and Vision Science, University of New South Wales, Kensington, New South Wales.

Purpose: To compare the ability of 24-2C and 10-2 test grids in measuring visual field global indices, identifying central visual field defects, and facilitating macular structure-function analysis with OCT scans in glaucoma and glaucoma suspect patients.

Design: Prospective, cross-sectional study.

Participants: One eye from 131 glaucoma and 57 glaucoma suspect patients recruited from a referral-only, university-based glaucoma clinic.

Methods: Each subject underwent perimetric testing using 24-2C SITA-Faster and 10-2 SITA-Fast in random order, and Cirrus OCT macular imaging (Ganglion Cell Analysis) for structure-function correlations.

Main Outcome Measures: Visual field global indices (mean deviation, pattern standard deviation, binarized "cluster" pass/fail, and central mean sensitivity), number and proportion of visual field defects, and structure-function concordance with the Cirrus OCT deviation map following visual field location displacement for correspondence with underlying retinal ganglion cell position.

Results: Global indices (mean deviation, pattern standard deviation, and central mean sensitivity) were similar between both grids. The 10-2 detected more defects compared with the 24-2C (P < 0.0001 for all patients, P = 0.006 for glaucoma patients). This was preserved when analyzing the proportion of defects in the central visual field for all patients (P = 0.02) but was not significantly different for glaucoma patients (P = 0.051). The 10-2 identified more central "clusters" of 2+ contiguous points of deficit (P < 0.0001). Structure-function comparisons performed at locations where visual field and OCT test locations were colocalized revealed greater concordance of structural and functional deficits using the 10-2 (P < 0.0001). The 10-2 took a median of 201 seconds, and the 24-2C took a median of 154 seconds, corresponding to the different thresholding algorithms.

Conclusions: The 24-2C and 10-2 test grids return similar global indices of visual field performance and proportionally similar amounts of central visual field loss. The additional points in the 10-2 grid return more "clusters" of defects and a greater rate of structure-function concordance compared with the 24-2C test grid. Thus, the 24-2C can identify the presence of a clustered central visual field defect using similar probability criteria, whereas the 10-2 may be more useful in comprehensively characterizing the defect and predicting central visual function.
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http://dx.doi.org/10.1016/j.ophtha.2021.03.014DOI Listing
March 2021

Headaches related to latanoprost in open-angle glaucoma.

Clin Exp Optom 2021 Mar 2:1-9. Epub 2021 Mar 2.

Centre for Eye Health, University of New South Wales, Kensington, NSW, Australia.

: The existing notion that topical latanoprost can lead to symptoms of headaches by reporting three cases of headache symptoms that developed following instillation of latanoprost prescribed as first-line therapy for newly diagnosed primary open-angle glaucoma (POAG) is explored in this case series.: Prostaglandin analogues (PGAs) are often used as first-line treatment in the treatment of POAG. An uncommon and infrequently reported side effect of PGAs is headaches.: A retrospective review of patient records was conducted on patients seen at the Centre for Eye Health between April 2016 and August 2017. Clinical findings, including outcomes following interventions such a punctal occlusion, as well as the proposed pharmacological mechanism underlying this phenomenon are presented and discussed.: Case 1 is a 62-year-old Caucasian male diagnosed with POAG and prescribed latanoprost in both eyes. At the follow-up visit, he reported waking up in with a dull throbbing headache following instillation of the eye drops the night before. Case 2 is a 58-year-old Asian male with POAG prescribed latanoprost to both eyes. Within a week, he developed symptoms of recurrent progressively worsening headaches post-instillation which persisted into the morning. Case 3 is a 75-year-old Caucasian male with POAG prescribed latanoprost for both eyes. He developed latanoprost sensitivity as well as headache symptoms associated with the eye drops which resolved followed its cessation. All patients reported initial symptoms of headaches associated with latanoprost use however the headaches were not persistent with intermittent punctal occlusion (cases 1 and 2) or intra-class drug rechallenge (case 3).: Although there may be a yet-undiscovered link between a headache response and latanoprost, these cases call to question the pharmacological relationship between latanoprost and headache symptoms. A systemic approach to critically examine the pathophysiological link between pharmacological therapy and potential adverse effects is proposed.
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http://dx.doi.org/10.1080/08164622.2021.1878846DOI Listing
March 2021

The performance and confidence of clinicians in training in the analysis of ophthalmic images within a work-integrated teaching model.

Ophthalmic Physiol Opt 2021 Mar 8. Epub 2021 Mar 8.

Centre for Eye Health, University of New South Wales, Kensington, New South Wales, Australia.

Purpose: A fundamental clinical skill is the recognition of artefacts within the outputs of advanced imaging modalities. However, current teaching programmes of healthcare practitioners are becoming increasingly challenged to provide practical exposure within an already crowded curriculum. This study evaluates the impact of a novel work-integrated teaching model on the confidence and competence of clinicians in the use of optical coherence tomography (OCT) and the recognition of its artefacts. The outcomes were then used to develop a model to predict performance and guide teaching strategies.

Methods: We prospectively evaluated a 6-week clinical placement for final year optometry students within a diagnostic eye clinic in 2018-2020. Participants completed a quiz on the identification of common OCT artefacts and rated their confidence levels on key areas of OCT application using a five-point Likert scale. Both were completed before (pre-rotation) and after (post-rotation) the placement. The cohort was divided into two groups; the first group was used to assess the impact of the placement and derive the prediction model for post-placement performance, which was then validated against the second group.

Results: A significant improvement in detecting OCT imaging artefacts was seen upon completion of the placement, which was greater in participants with lower entry level performance. Across all OCT artefact subtypes, there was an improvement in detecting segmentation error, delineation error and media opacities. A model predicting post-placement student performance was developed using entry level knowledge base as the key dependent variable. Self-rated confidence improved across all domains of OCT application but was not found to be a direct predictor of actual performance.

Conclusions: These results highlight the benefit of a work-integrated learning programme on both academic performance and confidence whilst identifying entry level knowledge base as the key variable predicting improvement. Tailored teaching incorporating entering knowledge is the best predictor of improvement during clinical placements. Integrating clinicians into a work-integrated setting with tailored teaching and comprehensive practical exposure can be an effective method for training future or current healthcare professionals.
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http://dx.doi.org/10.1111/opo.12795DOI Listing
March 2021

A combined convolutional and recurrent neural network for enhanced glaucoma detection.

Sci Rep 2021 Jan 21;11(1):1945. Epub 2021 Jan 21.

Vision Science Group, Graduate School of Health, University of Technology Sydney, Sydney, Australia.

Glaucoma, a leading cause of blindness, is a multifaceted disease with several patho-physiological features manifesting in single fundus images (e.g., optic nerve cupping) as well as fundus videos (e.g., vascular pulsatility index). Current convolutional neural networks (CNNs) developed to detect glaucoma are all based on spatial features embedded in an image. We developed a combined CNN and recurrent neural network (RNN) that not only extracts the spatial features in a fundus image but also the temporal features embedded in a fundus video (i.e., sequential images). A total of 1810 fundus images and 295 fundus videos were used to train a CNN and a combined CNN and Long Short-Term Memory RNN. The combined CNN/RNN model reached an average F-measure of 96.2% in separating glaucoma from healthy eyes. In contrast, the base CNN model reached an average F-measure of only 79.2%. This proof-of-concept study demonstrates that extracting spatial and temporal features from fundus videos using a combined CNN and RNN, can markedly enhance the accuracy of glaucoma detection.
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http://dx.doi.org/10.1038/s41598-021-81554-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820237PMC
January 2021

Authors' reply.

Ophthalmic Physiol Opt 2021 Jan 25;41(1):203-204. Epub 2020 Nov 25.

Centre for Eye Health, University of New South Wales, Kensington, Australia.

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http://dx.doi.org/10.1111/opo.12760DOI Listing
January 2021

Visualizing the Consistency of Clinical Characteristics that Distinguish Healthy Persons, Glaucoma Suspect Patients, and Manifest Glaucoma Patients.

Ophthalmol Glaucoma 2020 Jul - Aug;3(4):274-287. Epub 2020 Apr 26.

Centre for Eye Health, University of New South Wales, Kensington, Australia; School of Optometry and Vision Science, University of New South Wales, Kensington, Australia.

Purpose: To use factor analysis to visualize and assess the reproducibility and consistency of clinical quantitative parameters that can optimally distinguish among healthy, glaucoma suspect, and manifest glaucoma patients at a cross-sectional level and thus to describe the transition of quantitative change among the diagnostic categories.

Design: Retrospective cross-sectional study.

Participants: The medical records of healthy, glaucoma suspect, and manifest glaucoma patients (diagnosed by expert clinicians) seen at the Centre for Eye Health in 2015 (n = 148, n = 664, and n = 129, respectively) and 2018 (n = 242, n = 464, and n = 126, respectively) were reviewed. One eye was selected for the study.

Methods: Quantitative clinical measures (intraocular pressure [IOP], central corneal thickness [CCT], visual field [VF], and OCT) were extracted and binary logistic (backward stepwise) regression was performed to identify factors that dictated separation between diagnostic pairs. These were used systematically as inputs for factor analysis to determine a final model that could potentially predict a clinical diagnosis.

Main Outcome Measures: Intraocular pressure, CCT, VF (mean deviation and pattern standard deviation) indices, and OCT optic nerve head parameters and thickness values (retinal nerve fiber layer [RNFL] and ganglion cell-inner plexiform layer).

Results: Few clinical parameters were identified commonly as significant across all diagnostic pairings for 2015 (3 of 23: IOP, pattern standard deviation, and 7-o'clock RNFL thickness) and 2018 (1 of 23: vertical cup-to-disc ratio). Few parameters overlapped when comparing 2015 and 2018 results, highlighting inconsistencies in the models between years. Factor analysis showed good separation between healthy persons and glaucoma patients. Using biplots to visualize the data in 2-dimensional clusters, glaucoma suspect patients demonstrated substantial overlap with healthy and glaucoma cohorts. The contributions of each parameter to diagnostic separation changed between groups and years.

Conclusions: Despite advances in quantitative ocular imaging and perimetry, the transition among healthy, glaucoma suspect, and manifest glaucoma patients remains confounded by a lack of consistent, reproducible combinations of quantitative clinical criteria. These results highlight the nebulousness (at patient-, instrument-, and clinician-related levels) of glaucoma diagnosis that remains contingent on individual clinical expertise and assessment.
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http://dx.doi.org/10.1016/j.ogla.2020.04.009DOI Listing
April 2020

Validation of a novel functional test for assessing metamorphopsia using epiretinal membranes as a model.

Sci Rep 2020 09 10;10(1):14938. Epub 2020 Sep 10.

Centre for Eye Health, University of New South Wales, Kensington, NSW, Australia.

Current tests for assessing metamorphopsia do not account for confounders such as perceptual filling-in and spatial redundancy, which affect its sensitivity and repeatability. This proof-of-concept study aimed to assess the performance of a novel laboratory-based psychophysical test (Line Sag Test, LST) which addresses these issues for quantification of metamorphopsia in idiopathic epiretinal membranes. The LST quantifies perpendicular metamorphopsia at three eccentricities (3°, 6°, and 9°) along eight meridians (45° steps). Metamorphopsia was assessed using the LST and Amsler grid and the hit rates of both tests for detecting metamorphopsia were compared. Normal metamorphopsia scores using the LST did not differ significantly from 0 and fell within one step-size (p = 0.500). The LST detected significantly more cases of metamorphopsia than the Amsler grid (14/21 versus 3/21) (p = 0.003). Similarly, significantly more cases of visual distortions in asymptomatic iERMs were detected using the LST than the Amsler grid (11/18 versus 0/18) (p = 0.008). The LST has a higher hit rate compared to the Amsler grid (67% versus 14%). This work demonstrates a psychophysically-robust functional test addressing perceptual confounders is more sensitive for quantifying and localising metamorphopsia in macular disease, particularly in asymptomatic disease.
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http://dx.doi.org/10.1038/s41598-020-71627-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7484749PMC
September 2020

Management of open-angle glaucoma by primary eye-care practitioners: toward a personalised medicine approach.

Clin Exp Optom 2021 Apr 29;104(3):367-384. Epub 2021 Mar 29.

Ophthalmology Department, Prince of Wales Hospital, Sydney, Australia.

Glaucoma is the leading cause of irreversible blindness worldwide. As a chronic disease, glaucoma presents a significant burden to the individual, health-care provider and the health-care system. Currently, strategies for treating glaucoma are focused on lowering intraocular pressure, which is aimed at slowing or arresting disease progression over time. This is the only current accepted therapeutic strategy for glaucoma, and can be achieved using topical drugs, laser trabeculoplasty, filtration surgery or cyclodestructive techniques. The lowering of intraocular pressure has been well-supported by numerous large-scale seminal clinical trials in primary open-angle glaucoma, in both its early and advanced stages. Although such guidance remains current, in the last 10-years, there has been a significant evolution in preferred first-line therapies in the treatment of open-angle glaucoma with a resultant shift in practice patterns, particularly early in the course of the disease. These changes reflect both from the perspective of the doctor - in titrating the most effective and least risky treatment modality - and the perspective of the patient, in consenting to a treatment that preserves vision and results in minimal negative impact on quality of life. In this review, the most recent evidence regarding treatment modalities for early primary open-angle glaucoma is presented and an updated framework for management guidance is proposed.
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http://dx.doi.org/10.1111/cxo.13114DOI Listing
April 2021

Assessment of angle closure spectrum disease as a continuum of change using gonioscopy and anterior segment optical coherence tomography.

Ophthalmic Physiol Opt 2020 09 14;40(5):617-631. Epub 2020 Aug 14.

Centre for Eye Health, University of New South Wales, Kensington, New South Wales, Australia.

Purpose: Studies examining the anterior chamber angle and angle closure disease often compare quantitative angle information obtained using anterior segment optical coherence tomography (ASOCT) with one of several ordinal scales derived using gonioscopy. We test the assumption that the ordinal gonioscopic angle grades have equal step sizes and can be analysed using metric statistics.

Methods: The medical records of 214 consecutive patients who were referred for assessment of the anterior chamber angle were prospectively examined using gonioscopy and ASOCT (Spectralis Optical Coherence Tomography, OCT, www.heidelbergengineering.com). Anterior chamber angle parameters (angle opening distance, AOD, and trabecular-iris space area, TISA at 500 and 750 microns) were extracted from ASOCT images using a semi-automated segmentation algorithm written on MATLAB (www.mathworks.com). We first matched the quantitative values for each gonioscopic grade (0-4, from no structures visible to ciliary body visible) and described the frequency distributions to determine separability. We then applied a grade-agnostic clustering algorithm to determine the concordance between algorithm-clustered groups (using solely quantitative data) and those obtained using gonioscopy.

Results: The frequency distributions of the quantitative ASOCT parameters for each angle grade were mostly non-parametric and displayed unique distribution characteristics, with a floor effect seen for grade 0 and the lack of a ceiling effect seen for grades 3 and 4. Although we found significant differences in quantitative values across the five angle grades using the frequency distributions, some pairwise comparisons were indistinguishable (such as grades 0 and 1, and grades 3 and 4) due to the overlaps in distributions. On average, differences in quantitative values were consistent between gonioscopic grade steps, but there remained substantial variability that confounds prediction of change between ordinal steps. The clustering algorithm showed approximately 10% of cases with the same group assignment as that of the gonioscopic grade, improving slightly to 30% when the top 5% of quantitative data were excluded from analysis.

Conclusions: Our results do not necessarily support the assumption that the ordinal scales used in gonioscopy can be interpreted using an interval scale. We highlight the need for better methods of describing the course and risk of angle closure spectrum disease to identify disease progression and conversion, where gonioscopy remains the gold standard.
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http://dx.doi.org/10.1111/opo.12721DOI Listing
September 2020

A Strategy for Seeding Point Error Assessment for Retesting (SPEAR) in Perimetry Applied to Normal Subjects, Glaucoma Suspects, and Patients With Glaucoma.

Am J Ophthalmol 2021 01 8;221:115-130. Epub 2020 Aug 8.

Centre for Eye Health and the School of Optometry and Vision Science, University of New South Wales, Kensington, New South Wales, Australia.

Purpose: We sought to determine the impact of seeding point errors (SPEs) as a source of low test reliability in perimetry and to develop a strategy to mitigate this error early in the test.

Design: Cross-sectional study.

Methods: Visual field test results from 1 eye of 364 patients (77 normal eyes, 178 glaucoma suspect eyes, and 109 glaucoma eyes) were used to develop models for identifying SPE. Two test cohorts (326 undertaking Swedish interactive thresholding algorithm [SITA]-Faster and 327 glaucoma eyes undertaking SITA-Standard) were used to prospectively evaluate the models for identifying SPEs. Global visual field metrics were compared among reliable and unreliable results. Regression models were used to identify factors distinguishing SPEs from non-SPEs. Models were evaluated using receiver operating characteristic (ROC) curves.

Results: In the test cohorts, SITA-Faster produced a higher rate of unreliable visual field results (30%-49.7%) compared with SITA-Standard (10.8%-16.6%). SPEs contributed to most of the unreliable results in SITA-Faster (57.5%-64.9%) compared with gaze tracker deviations accounting for most of the unreliable results in SITA-Standard (40%-77.8%). In SITA-Faster, results with SPEs had worse global indices and more clusters of sensitivity reduction than reliable results. Our best model (using 9 test locations) can identify SPEs with an area under the ROC curve of 0.89.

Conclusion: SPEs contribute to a large proportion of unreliable visual field test results, particularly when using SITA-Faster. We propose a useful model for identifying SPEs early in the test that can then guide retesting using both SITA algorithms. We provide a simplified framework for the perimetrist to improve the overall fidelity of the test result.
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http://dx.doi.org/10.1016/j.ajo.2020.07.047DOI Listing
January 2021

Cluster analysis reveals patterns of age-related change in anterior chamber depth for gender and ethnicity: clinical implications.

Ophthalmic Physiol Opt 2020 09 9;40(5):632-649. Epub 2020 Jul 9.

Centre for Eye Health, University of New South Wales, Kensington, NSW, Australia.

Purpose: To identify patterns of age-, gender- and refractive- related changes in Scheimpflug-based anterior chamber depth across the central 8 mm of chamber width, to derive normative models, potentially useful for angle closure disease diagnosis.

Methods: This was a retrospective, cross-sectional study. Scheimpflug photography was used to obtain anterior chamber depth measurements at 57 points across the central 8 mm of the chamber width from one eye of each healthy subject (male Caucasians (n = 189), female Caucasians (n = 186), male Asians (n = 165) and female Asians (n = 181)). Sliding window and nonlinear regression analysis was used to identify the age-related changes in chamber depth. Hierarchical cluster analysis was used to identify test locations with statistically identical age-related shifts, which were used to perform age-correction for all subjects, resulting in normative distributions of chamber depth across the chamber width. The model was examined with and without the contribution of spherical equivalent refractive error.

Results: Distinct clusters, demonstrating statistically indistinguishable age-related changes of chamber depth over time, were identified. These age-related changes followed a nonlinear regression (fifth or sixth order polynomial). Females tended to have a greater rate of chamber depth shallowing. Incorporating refractive error into the model produced minimal changes to the fit relative to the ground truth. Comparisons with cut-offs for angle closure from the literature showed that ageing alone was insufficient for identifying angle closure disease.

Conclusions: Age-, ethnicity- and gender-related differences need to be acknowledged in order to utilise anterior chamber depth data for angle closure disease diagnosis correctly. Ageing alone does not adequately account for the angle closure disease process.
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http://dx.doi.org/10.1111/opo.12714DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540376PMC
September 2020

Ability of 24-2C and 24-2 Grids to Identify Central Visual Field Defects and Structure-Function Concordance in Glaucoma and Suspects.

Am J Ophthalmol 2020 11 2;219:317-331. Epub 2020 Jul 2.

Centre for Eye Health, University of New South Wales, Kensington, New South Wales, Australia; School of Optometry and Vision Science, University of New South Wales, Kensington, New South Wales, Australia.

Purpose: The purpose of this study was to compare the ability of the 24-2 test grid with that of the 24-2C test grid to measure visual field global indices, identify central visual field defects, and facilitate macular structure-function analysis with optical coherence tomography (OCT) scans in glaucoma suspects and glaucoma patients.

Design: Prospective, cross-sectional study.

Methods: One eye from each of 100 glaucoma suspects and glaucoma patients (60 undergoing SITA-Faster [Zeiss Meditec] testing on 24-2 and 24-2C; 40 undergoing SITA-Standard [Zeiss Meditec] testing on 24-2 and SITA-Faster on 24-2C) were included in the study. Global visual field indices, test duration, and pattern deviation results were extracted. The deviation map from the Cirrus OCT (Carl Zeiss Meditec) Ganglion Cell Analysis (GCA) was extracted, and structure-function relationships were compared after correction of the visual field test stimulus location that stimulated the corresponding retinal ganglion cell.

Results: Global index results of the 24-2 grid were similar to those of the 24-2C grid, and both identified a comparable number of clusters of visual field defects. Centrally, the 24-2C grid identified more clusters of defects than the 24-2 grid, but this was not statistically significant. Although the 24-2C test locations resulted in more instances of structure-function concordance than the 24-2 locations, half the locations in the 24-2C grid fell close to or outside the GCA grid when corrected for ganglion cell displacement.

Conclusions: The 24-2C returned global visual field indices similar to the 24-2 grid but tended to identify more clusters of central functional defects. Central structure-function concordance was better achieved using the 24-2C grid, but half of the visual field test locations did not coincide with the commonly used macular thickness scan.
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http://dx.doi.org/10.1016/j.ajo.2020.06.024DOI Listing
November 2020

Determining Significant Elevation of Intraocular Pressure Using Self-tonometry.

Optom Vis Sci 2020 02;97(2):86-93

Centre for Eye Health and School of Optometry and Vision Science, University of New South Wales, Kensington, New South Wales, Australia.

Significance: Icare HOME rebound tonometry is increasingly adopted into clinical practice for IOP phasing of glaucoma patients and suspects. Because of measurement differences with applanation tonometry and diurnal fluctuations, interpretation of the IOP measured with Icare HOME phasing can be challenging.

Purpose: The purpose of this study was to use a large patient cohort to develop a practical, analytical tool for interpreting Icare HOME measurements with respect to applanation pressure.

Methods: IOP measurements using the Icare HOME and an applanation tonometer were taken prospectively in 498 consecutive patients. Bland-Altman, frequency distribution, and linear regression analysis were applied to determine measurement differences. A novel criterion, Threshold Icare HOME IOP, was developed to assist identification of elevation above target applanation pressure, considering the expected diurnal variation and measurement variability.

Results: Icare HOME tended to underestimate applanation tonometry (mean bias, -1.7 mmHg; 95% limits of agreement, -7.0 to +3.6). Overall, differences were within ±3 mmHg in 71.5% and ±5 mmHg in 92% of patients. Based on the novel criterion developed, Icare HOME measurements that exceed target applanation pressure by 6 mmHg or greater are generally outside the 95% limit of expected observations.

Conclusions: The Threshold Icare HOME IOP is a novel and practical criterion that can assist clinicians in their interpretation of Icare HOME phasing measurements with respect to target applanation pressures. Elevation above the expected thresholds may prompt closer monitoring or even modifications to glaucoma management.
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http://dx.doi.org/10.1097/OPX.0000000000001478DOI Listing
February 2020

Anterior Chamber Angle Evaluation Using Gonioscopy: Consistency and Agreement between Optometrists and Ophthalmologists.

Optom Vis Sci 2019 10;96(10):751-760

Centre for Eye Health, University of New South Wales, Kensington, New South Wales, Australia.

Significance: In our intermediate-tier glaucoma care clinic, we demonstrate fair to moderate agreement in gonioscopy examination between optometrists and ophthalmologists, but excellent agreement when considering open versus closed angles. We highlight the need for increased consistency in the evaluation and recording of angle status using gonioscopy.

Purpose: The consistency of gonioscopy results obtained by different clinicians is not known but is important in moving toward practice modalities such as telemedicine and collaborative care clinics. The purpose of this study was to evaluate the description and concordance of gonioscopy results among different practitioners.

Methods: The medical records of 101 patients seen within a collaborative care glaucoma clinic who had undergone gonioscopic assessment by two clinicians (one optometrist and either one general ophthalmologist [n = 50] or one glaucoma specialist [n = 51]) were reviewed. The gonioscopy records were evaluated for their descriptions of deepest structure seen, trabecular pigmentation, iris configuration, and other features. These were compared between clinicians (optometrist vs. ophthalmologist) and against the final diagnosis.

Results: Overall, 51.9 and 59.8% of angles were graded identically in terms of deepest visible structure when comparing between optometrist versus general ophthalmologist and optometrist versus glaucoma specialist, respectively. The concordance increased when considering ±1 of the grade (67.4 and 78.5%, respectively), and agreement with the final diagnosis was high (>90%). Variations in angle grading other than naming structures were observed (2.0, 30, and 3.9% for optometrist, general ophthalmologist, and glaucoma specialist, respectively). Most of the time, trabecular pigmentation or iris configuration was not described.

Conclusions: Fair to moderate concordance in gonioscopy was achieved between optometrists and ophthalmologists in a collaborative care clinic in which there is consistent feedback and clinical review. To move toward unified medical records and a telemedicine model, improved consistency of record keeping and angle description is required.
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http://dx.doi.org/10.1097/OPX.0000000000001432DOI Listing
October 2019

Remote Grading of the Anterior Chamber Angle Using Goniophotographs and Optical Coherence Tomography: Implications for Telemedicine or Virtual Clinics.

Transl Vis Sci Technol 2019 Sep 25;8(5):16. Epub 2019 Sep 25.

Centre for Eye Health, University of New South Wales, Kensington, NSW, Australia.

Purpose: To evaluate the agreement and accuracy of grading goniophotographs and anterior segment optical coherence tomography (AS-OCT) results for assessment of the anterior chamber angle, and elicit factors driving concordance between perceived grade and ground truth.

Methods: Three clinicians evaluated the goniophotographs and AS-OCT results of 75 patients. Graders' impressions of the angle grade, trabecular pigmentation, and iris contour were compared with the ground truth gonioscopic examination result when physically performed by a senior optometrist. Percentage agreement and kappa statistics were calculated. Binary logistic regression was used to elicit factors for accurate grading.

Results: Exact angle matches and binary (open or closed) evaluations were above guessing rate for all graders. There was a systematic bias toward underestimating the angle structure across all graders, especially at the superior angle, by approximately 1 ordinal unit. Kappa statistics showed fair-moderate agreement for exact (0.387-0.520) and binary (0.347-0.520) angle evaluations. Agreement was unchanged when using a multimodal approach (0.373-0.523). Factors driving concordance were primarily related to the extremes of the anterior chamber angle configuration (shallow or deep structures, and iris contour). However, prediction models did not fully explain the levels of concordance with the ground truth (maximum amongst models 0.177).

Conclusions: Although moderate agreement between graders and ground truth could be obtained under binary evaluations, angle grades were generally underestimated. Factors affecting concordance were primarily the extremes of the ground truth angle and iris contour.

Translational Relevance: We highlight factors affecting accuracy of grading goniophotography and AS-OCT images of the anterior chamber angle.
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http://dx.doi.org/10.1167/tvst.8.5.16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6761908PMC
September 2019

Clinical Evaluation of Swedish Interactive Thresholding Algorithm-Faster Compared With Swedish Interactive Thresholding Algorithm-Standard in Normal Subjects, Glaucoma Suspects, and Patients With Glaucoma.

Am J Ophthalmol 2019 12 27;208:251-264. Epub 2019 Aug 27.

Centre for Eye Health, University of New South Wales, Kensington, New South Wales; School of Optometry and Vision Science, University of New South Wales, Kensington, New South Wales.

Purpose: To compare the visual fields results obtained using the Swedish interactive thresholding algorithm-Standard (SS) and the Swedish interactive thresholding algorithm-Faster (SFR) in normal subjects, glaucoma suspects, and patients with glaucoma and to quantify potential time-saving benefits of the SFR algorithm.

Design: Prospective, cross-sectional study.

Methods: One randomly selected eye from 364 patients (77 normal subjects, 178 glaucoma suspects, and 109 patients with glaucoma) seen in a single institution underwent testing using both SS and SFR on the Humphrey Field Analyzer. Cumulative test time using each algorithm was compared after accounting for different rates of test reliability. Pointwise and cluster analysis was performed to determine whether there were systematic differences between algorithms.

Results: Using SFR had a greater rate of unreliable results (29.3%) compared with SS (7.7%, P < .0001). This was mainly because of high false positive rates and seeding point errors. However, modeled test times showed that using SFR could obtain a greater number of reliable results within a shorter period of time. SFR resulted in higher sensitivity values (on average 0.5 dB for patients with glaucoma) that was greater under conditions of field loss (<19 dB). Cluster analysis showed no systematic patterns of sensitivity differences between algorithms.

Conclusions: After accounting for different rates of test reliability, SFR can result in significant time savings compared with SS. Clinicians should be cognizant of false positive rates and seeding point errors as common sources of error for SFR. Results between algorithms are not directly interchangeable, especially if there is a visual field deficit <19 dB.
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http://dx.doi.org/10.1016/j.ajo.2019.08.013DOI Listing
December 2019

Modeling Changes in Corneal Parameters With Age: Implications for Corneal Disease Detection.

Am J Ophthalmol 2020 01 27;209:117-131. Epub 2019 Aug 27.

Centre for Eye Health and the School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia. Electronic address:

Purpose: To apply computational methods to model normal age-related changes in corneal parameters and to establish their association with demographic factors, thereby providing a framework for improved detection of subclinical corneal ectasia (SCE).

Design: Cross-sectional study.

Methods: One hundred seventeen healthy participants were enrolled from Centre for Eye Health (Sydney, Australia). Corneal thickness (CT), front surface sagittal curvature (FSSC), and back surface sagittal curvature (BSSC) measurements were extracted from 57 corneal locations from 1 eye per participant using the Pentacam HR. Cluster analyses were performed to identify locations demonstrating similar variations with age. Age-related changes were modeled using polynomial regression with sliding window methods, and model accuracy was verified with Bland-Altman comparisons. Pearson correlations were applied to examine the impacts of demographic factors.

Results: Concentric cluster patterns were observed for CT and FSSC but not for BSSC. Sliding window analyses were best fit with quartic and cubic regression models for CT and FSSC/BSSC, respectively. CT and FSSC sliding window models had narrower 95% limits of agreement compared with decade-based models (0.015 mm vs 0.017 mm and 0.14 mm vs 0.27 mm, respectively), but were wider for BSSC than decade-based models (0.73 mm vs 0.54 mm). Significant correlations were observed between CT and astigmatism (P = .02-.049) and FSSC and BSSC and gender (P = <.001-.049).

Conclusions: The developed models robustly described aging variations in CT and FSSC; however, other mechanisms appear to contribute to variations in BSSC. These findings and the identified correlations provide a framework that can be applied to future model development and establishment of normal databases to facilitate SCE detection.
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http://dx.doi.org/10.1016/j.ajo.2019.08.014DOI Listing
January 2020

Contrast sensitivity isocontours of the central visual field.

Sci Rep 2019 08 12;9(1):11603. Epub 2019 Aug 12.

Centre for Eye Health, The University of New South Wales, Kensington, New South Wales, Australia.

Standard automated perimetry (SAP), the most common form of perimetry used in clinical practice, is associated with high test variability, impacting clinical decision making and efficiency. Contrast sensitivity isocontours (CSIs) may reduce test variability in SAP by identifying regions of the visual field with statistically similar patterns of change that can be analysed collectively and allow a point (disease)-to-CSI (normal) comparison in disease assessment as opposed to a point (disease)-to-point (normal) comparison. CSIs in the central visual field however have limited applicability as they have only been described using visual field test patterns with low, 6° spatial sampling. In this study, CSIs were determined within the central 20° visual field using the 10-2 test grid paradigm of the Humphrey Field Analyzer which has a high 2° sampling frequency. The number of CSIs detected in the central 20° visual field was greater than previously reported with low spatial sampling and stimulus size dependent: 6 CSIs for GI, 4 CSIs for GII and GIII, and 3 CSIs for GIV and GV. CSI number and distribution were preserved with age. Use of CSIs to assess visual function in age-related macular degeneration (AMD) found CSI guided analysis detected a significantly greater deviation in sensitivity of AMD eyes from normal compared to a standard clinical pointwise comparison (-1.40 ± 0.15 dB vs -0.96 ± 0.15 dB; p < 0.05). This work suggests detection of CSIs within the central 20° is dependent on sampling strategy and stimulus size and normative distribution limits of CSIs can indicate significant functional deficits in diseases affecting the central visual field such as AMD.
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http://dx.doi.org/10.1038/s41598-019-48026-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6691009PMC
August 2019

A collaborative care pathway for patients with suspected angle closure glaucoma spectrum disease.

Clin Exp Optom 2020 03 23;103(2):212-219. Epub 2019 May 23.

Centre for Eye Health, The University of New South Wales, Kensington, New South Wales, Australia.

Background: Currently, no specific collaborative care pathway exists that distinguishes open angle glaucoma from narrow angle or angle closure disease. This study evaluates a newly developed referral and collaborative care pathway specifically for patients with angle closure spectrum disease.

Methods: The medical records of consecutive patients referred to the Centre for Eye Health for glaucoma assessment were examined, six months before (Pre Suite) and after (Post Suite) the introduction of a novel referral pathway for anterior chamber angle assessment (Angle Suite). Patient demographic and clinical data, the referral letter and practitioner characteristics were extracted.

Results: Angle Suite (n = 77) patients had an appointment much sooner compared to Pre (n = 383) and Post Suite (n = 425) patients (p < 0.0001). Following the introduction of Angle Suites, there was a reduction of incidental angle closure disease found in routine, non-angle closure glaucoma assessment. Onward referral was required by 36.4 per cent of patients referred for suspected angle closure disease, while the rest could be discharged back into the community (13.0 per cent) or reviewed at the Centre for Eye Health (50.6 per cent). Multinomial logistic regression found that the presence of an angle description in the referral letter improved the true positive rate for angle closure disease (p < 0.0001).

Conclusions: The clinical pathway may reduce the number of incidental angle closure patients and improved the timeliness of appropriate clinical care delivered to a subset of patients who may benefit from prompt medical attention. This pathway provides an opportunity for appropriately staffed and equipped collaborative care clinics to reduce the burden on tertiary level ophthalmic facilities.
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http://dx.doi.org/10.1111/cxo.12923DOI Listing
March 2020

Development of a Spatial Model of Age-Related Change in the Macular Ganglion Cell Layer to Predict Function From Structural Changes.

Am J Ophthalmol 2019 12 10;208:166-177. Epub 2019 May 10.

Centre for Eye Health, University of New South Wales, Sydney, New South Wales, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia. Electronic address:

Purpose: To develop location-specific models of normal, age-related changes in the macular ganglion cell layer (GCL) from optical coherence tomography (OCT). Using these OCT-derived models, we predicted visual field (VF) sensitivities and compared these results to actual VF sensitivities.

Design: Retrospective cohort study.

Methods: Single eyes of 254 normal participants were retrospectively enrolled from the Centre for Eye Health (Sydney, Australia). Macular GCL measurements were obtained using Spectralis OCT. Cluster algorithms were performed to identify spatial patterns demonstrating similar age-related change. Quadratic and linear regression models were subsequently used to characterize age-related GCL decline. Forty participants underwent additional testing with Humphrey VFs, and 95% prediction intervals were calculated to measure the predictive ability of structure-function models incorporating cluster-based pooling, age correction, and consideration of spatial summation.

Results: Quadratic GCL regression models provided a superior fit (P value <.0001-.0066), establishing that GCL decline commences in the late 30s across the macula. The equivalent linear rates of GCL decline showed eccentricity-dependent variation (0.13 μm/yr centrally vs 0.06 μm/yr peripherally); however, average, normalized GCL loss per year was consistent across the 64 macular measurement locations at 0.26%. The 95% prediction intervals describing predicted VF sensitivities were significantly narrower across all cluster-based structure-function models (3.79-4.99 dB) compared with models without clustering applied (5.66-6.73 dB, P < .0001).

Conclusions: Combining spatial clustering with age-correction based on regression models allowed the development of robust models describing GCL changes with age. The resultant superior predictive ability of VF sensitivity from ganglion cell measurements may be applied to future models of disease development to improve detection of early macular GCL pathology.
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http://dx.doi.org/10.1016/j.ajo.2019.04.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6842123PMC
December 2019

Optimising the Structure-Function Relationship at the Locus of Deficit in Retinal Disease.

Front Neurosci 2019 9;13:306. Epub 2019 Apr 9.

School of Optometry and Vision Science, The University of New South Wales, Kensington, NSW, Australia.

Technologies such as optical coherence tomography have facilitated the visualization of anatomical tissues such as that of the retina. The availability of retinal anatomical data has led to the hypothesis that it may be able to accurately predict visual function from anatomical information. However, accurate determination of the structure-function relationship has remained elusive in part due to contributions of non-retinal sources of variability, thus imposing potential limitations in the fidelity of the relationship. Furthermore, differences in manifestation of functional loss due to different retinal loci of change (inner retina or outer retinal elements) have also been the subject of debate. Here, we assessed the application of a novel, more objective psychophysical paradigm to better characterize the relationship between functional and structural characteristics in the eye. Using ocular diseases with known loci of anatomical change (glaucoma, inner retinal loss; and retinitis pigmentosa, outer retinal loss), we compared conventional more subjective psychophysical techniques that may be contaminated by the presence of non-retinal sources of variability with our more objective approach. We show that stronger correlations between underlying retinal structure and visual function can be achieved across a breadth of anatomical change by using a more objective psychophysical paradigm. This was independent of the locus of structural loss (at the ganglion cells for glaucoma or photoreceptors for retinitis pigmentosa), highlighting the role of downstream retinal elements to serve as anatomical limiting factors for studying the structure-function relationship. By reducing the contribution of non-retinal sources of variability in psychophysical measurements, we herein provide a structure-function model with higher fidelity. This reinforces the need to carefully consider the psychophysical protocol when examining the structure-function relationship in sensory systems.
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http://dx.doi.org/10.3389/fnins.2019.00306DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6467237PMC
April 2019

An evidence-based approach to the routine use of optical coherence tomography.

Clin Exp Optom 2019 05 17;102(3):242-259. Epub 2018 Dec 17.

Centre for Eye Health, The University of New South Wales, Sydney, New South Wales, Australia.

Optical coherence tomography is an imaging technology that has revolutionised the detection, assessment and management of ocular disease. It is now a mainstream technology in clinical practice and is performed by non-specialised personnel in some settings. This article provides a clinical perspective on the implications of that movement and describes best practice using multimodal imaging and an evidence-based approach. Practical, illustrative guides on the interpretation of optical coherence tomography are provided for three major diseases of the ocular fundus, in which optical coherence tomography is often crucial to management: age-related macular degeneration, diabetic retinopathy and glaucoma. Topics discussed include: cross-sectional and longitudinal signs in ocular disease, so-called 'red-green' disease whereby clinicians rely on machine/statistical comparisons for diagnosis in managing treatment-naïve patients, and the utility of optical coherence tomography angiography and machine learning.
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http://dx.doi.org/10.1111/cxo.12847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6590481PMC
May 2019

Differences in Static and Kinetic Perimetry Results are Eliminated in Retinal Disease when Psychophysical Procedures are Equated.

Transl Vis Sci Technol 2018 Sep 1;7(5):22. Epub 2018 Oct 1.

School of Optometry and Vision Science, University of New South Wales, Kensington, NSW, Australia.

Purpose: We tested the hypothesis that clinical statokinetic dissociation (SKD, defined as the difference in sensitivity to static and kinetic stimuli) at the scotoma border in retinal disease is due to individual criterion bias and that SKD can be eliminated by equating the psychophysical procedures for testing static and kinetic stimulus detection.

Methods: Six subjects with glaucoma and six with retinitis pigmentosa (RP) were tested. Clinical procedures (standard automated perimetry [SAP] and manual kinetic perimetry [MKP]) were used to determine clinical SKD and the region of interest for laboratory-based testing. Two-way Method of Limits (MoL) was used to establish the isocontrast region at the scotoma border in glaucoma and RP subjects. Method of Constant Stimuli (MoCS) and a two-interval forced choice (2IFC) procedure then were used to present static or kinetic (inward or outward) stimuli at different eccentricities within the isocontrast region. The results were fitted with psychometric functions to determine threshold eccentricities.

Results: Clinical SKD was found in glaucoma and RP subjects, with variable magnitude among subjects, but significantly exceeding expected typical measurement variability. The resultant psychometric functions when using MoCS and 2IFC showed equal sensitivity to static and kinetic targets, thus eliminating SKD.

Conclusions: Clinical SKD found using clinical techniques is due to methodologic differences and criterion bias, and is eliminated by using an equated and more objective psychophysical task, similar to normal subjects.

Translational Relevance: Eliminating SKD using a psychophysical approach minimizing criterion bias suggests that it is not useful to distinguish between normal and diseased fields.
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http://dx.doi.org/10.1167/tvst.7.5.22DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6166892PMC
September 2018

Neutralizing Peripheral Refraction Eliminates Refractive Scotomata in Tilted Disc Syndrome.

Optom Vis Sci 2018 10;95(10):959-970

Centre for Eye Health, University of New South Wales, Kensington, New South Wales, Australia.

Significance: We demonstrate that the visual field defects in patients with tilted disc syndrome can be reduced or eliminated by neutralizing the peripheral scotoma in the area of posterior retinal bowing, which may allow differentiation between a congenital anomaly and acquired pathology.

Purpose: Tilted disc syndrome is a congenital and unchanging condition that may present with visual field defects mimicking loss seen in neurological diseases, such as transsynaptic retrograde degeneration. Our purpose was to systematically investigate the ability of a neutralized peripheral refraction to eliminate refractive visual field defects seen in tilted disc syndrome. This was compared with the same technique performed on patients with neurological deficits.

Methods: The Humphrey Field Analyzer was used to measure sensitivities across the 30-2 test grid in 14 patients with tilted disc syndrome using four refractive corrections: habitual near correction and with an additional -1.00, -2.00 or -3.00 D negative lens added as correction lenses. Peripheral refractive errors along the horizontal meridian were determined using peripheral retinoscopy and thus allowed calculation of residual peripheral refraction with different levels of refractive correction. Visual field defects were assessed qualitatively and quantitatively using sensitivities and probability scores in both patient groups.

Results: A smaller residual refractive error after the application of negative addition lenses correlated with improvement in visual field defects in terms of sensitivity and probability scores in patients with tilted disc syndrome. Patients with established neurological deficits (retrograde degeneration) showed improvement in sensitivities but not in probability scores.

Conclusions: Neutralizing the refractive error at the region of posterior retinal bowing due to tilted disc syndrome reduces the apparent visual field defect. This may be a useful and rapid test to help differentiate between tilted disc syndrome and other pathological causes of visual field defects such as neurological deficits.
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http://dx.doi.org/10.1097/OPX.0000000000001286DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6166693PMC
October 2018

Application of Pattern Recognition Analysis to Optimize Hemifield Asymmetry Patterns for Early Detection of Glaucoma.

Transl Vis Sci Technol 2018 4;7(5). Epub 2018 Sep 4.

Centre for Eye Health, University of New South Wales, Kensington, NSW, Australia.

Purpose: To assess the diagnostic utility of a new hemifield asymmetry analysis derived using pattern recognition contrast sensitivity isocontours (CSIs) within the Humphrey Field Analyzer (HFA) 24-2 visual field (VF) test grid. The performance of an optimal CSI-derived map was compared against a commercially available clustering method (Glaucoma Hemifield Test, GHT).

Methods: Five hundred VF results of 116 healthy subjects were used to determine normative distribution limits for comparisons. Pattern recognition analysis was applied to HFA 24-2 sensitivity data to determine CSI theme maps delineating clusters for hemifield comparisons. Then, 1019 VF results from 228 glaucoma patients were assessed using different clustering methods to determine the true-positive rate. We also assessed additional 354 VF results of 145 healthy subjects to determine the false-positive rate.

Results: The optimum clustering method was the CSI-derived seven-theme class map, which identified more glaucomatous VFs compared with the GHT map. The seven-class theme map also identified more cases compared with the five-, six-, and eight-class maps, suggesting no effect of number of clusters. Integrating information regarding the location of glaucomatous defects to the CSI clusters did not improve detection rate.

Conclusions: A clustering map derived using CSIs improved detection of glaucomatous VFs compared with the currently available GHT. An optimized CSI-derived map may serve as an additional means to aid earlier detection of glaucoma.

Translational Relevance: Pattern recognition-derived theme maps provide a means for guiding test point selection for asymmetry analysis in glaucoma assessment.
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http://dx.doi.org/10.1167/tvst.7.5.3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6126954PMC
September 2018

A Method Using Goldmann Stimulus Sizes I to V-Measured Sensitivities to Predict Lead Time Gained to Visual Field Defect Detection in Early Glaucoma.

Transl Vis Sci Technol 2018 May 7;7(3):17. Epub 2018 Jun 7.

Centre for Eye Health, University of New South Wales Sydney, Sydney, NSW, Australia.

Purpose: To predict the lead time (difference in time taken for a visual field [VF] defect to be detected) obtained when using stimulus sizes within or near the size of the critical area of spatial summation (Ac), and to test these predictions using sensitivity measurements from a cohort of glaucoma patients.

Methods: Thirty-seven patients with early open-angle glaucoma and 60 healthy observers underwent VF testing on the Humphrey Field Analyzer in full threshold mode using Goldmann stimulus sizes I to V (GI-V) across the 30-2 test grid. We used the sensitivities measured using GI to V in healthy patients to predict the lead time gained by using stimulus sizes within the size of Ac at all locations within the 30-2 grid. Then, we used sensitivities measured in the glaucoma patients to test this predictive model.

Results: Median lead time to VF defect detection when using stimulus sizes within Ac compared with stimulus sizes larger than Ac was 4.1 years across the 30-2 test grid (interquartile range, 3.1 and 5.1 years). Sensitivities of the glaucoma patients showed good agreement with the predictive model of lead time gained (77.5%-84.3% were within ±3 dB).

Conclusions: Our model predicted substantial lead time differences when using stimulus sizes within or near Ac. Such stimulus sizes could potentially detect VF defects, on average, 4 years earlier than current paradigms.

Translational Relevance: Stimulus sizes within or near Ac may be more suitable for early detection of glaucomatous VF defects. Larger stimulus sizes may be more suitable for later monitoring of established disease.
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http://dx.doi.org/10.1167/tvst.7.3.17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5993363PMC
May 2018

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

Invest Ophthalmol Vis Sci 2018 04;59(5):1693-1703

Centre for Eye Health, University of New South Wales, New South Wales, Australia.

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: R2 = 0.41-0.43, GIII-GV: R2 = 0.16-0.41) and diseased cohorts (GI-GII: R2 = 0.33-0.41, GIII-GV: R2 = 0.19-0.36). Quadratic regression curves for combined GI to V data demonstrated high correlation (R2= 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 structure-function 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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http://dx.doi.org/10.1167/iovs.17-23683DOI Listing
April 2018

Reducing Spatial Uncertainty Through Attentional Cueing Improves Contrast Sensitivity in Regions of the Visual Field With Glaucomatous Defects.

Transl Vis Sci Technol 2018 Mar 23;7(2). Epub 2018 Mar 23.

School of Optometry and Vision Science, University of New South Wales, Kensington, NSW, Australia.

Purpose: Current clinical perimetric test paradigms present stimuli randomly to various locations across the visual field (VF), inherently introducing spatial uncertainty, which reduces contrast sensitivity. In the present study, we determined the extent to which spatial uncertainty affects contrast sensitivity in glaucoma patients by minimizing spatial uncertainty through attentional cueing.

Methods: Six patients with open-angle glaucoma and six healthy subjects underwent laboratory-based psychophysical testing to measure contrast sensitivity at preselected locations at two eccentricities (9.5° and 17.5°) with two stimulus sizes (Goldmann sizes III and V) under different cueing conditions: 1, 2, 4, or 8 points verbally cued. Method of Constant Stimuli and a single-interval forced-choice procedure were used to generate frequency of seeing (FOS) curves at locations with and without VF defects.

Results: At locations with VF defects, cueing minimizes spatial uncertainty and improves sensitivity under all conditions. The effect of cueing was maximal when one point was cued, and rapidly diminished when more points were cued (no change to baseline with 8 points cued). The slope of the FOS curve steepened with reduced spatial uncertainty. Locations with normal sensitivity in glaucomatous eyes had similar performance to that of healthy subjects. There was a systematic increase in uncertainty with the depth of VF loss.

Conclusions: Sensitivity measurements across the VF are negatively affected by spatial uncertainty, which increases with greater VF loss. Minimizing uncertainty can improve sensitivity at locations of deficit.

Translational Relevance: Current perimetric techniques introduce spatial uncertainty and may therefore underestimate sensitivity in regions of VF loss.
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http://dx.doi.org/10.1167/tvst.7.2.8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5868861PMC
March 2018