Faculty Bibliography

Purpose : Vivid Vision Perimetry (VVP) is a novel method for performing in-office and home-based visual field assessment using a virtual reality platform and oculokinetic perimetry. The purpose of this study was to examine the test-retest reproducibility of the VVP platform. Methods : Subjects with open-angle glaucoma and glaucoma suspects were prospectively enrolled and underwent visual field analysis across 54 test locations in a 24-2 pattern using the VVP device (Vivid Vision, San Francisco, CA). Each subject was examined in 2 sessions, and the mean sensitivity (dB) was the primary outcome measure obtained for each eye in both sessions. The repeatability of mean sensitivity was assessed through analysis of bias from the differences between the two VVP sessions. A Bland-Altman plot using a mixed effects model (adjusting for average sensitivity and eye correlation) was created to illustrate the level of agreement between repeated measurements. Results : Fourteen eyes of 7 open-angle glaucoma patients and 10 eyes of 5 glaucoma suspects were enrolled (mean age 62.3 +/-9.3 years, 33% female). Based on the data from 24 eyes, the average difference of VVP mean sensitivity between the two sessions was found to be 0.48 dB. Three eyes (12.5%) fell outside the upper and lower limits of agreement (95% CI:-1.15, 2.11). The level of agreement between repeated VVP measurements showed a general trend of increasing precision as mean sensitivity values increased (Figure 1). Conclusions : The VVP platform provides reproducible visual field sensitivity measurements for glaucoma patients and glaucoma suspects and represents a novel approach for glaucoma monitoring. These data suggest that VVP measurement repeatability is consistent with standard automated perimetry

Purpose : Current GPU memory limitations do not support the analysis of OCT scans at its original resolution, and previous techniques have downsampled the inputs considerably which resulted in a loss of detail. Here, we utilise a new memory management support framework that allows for the training of large deep learning networks and apply it to the detection of glaucoma in OCT scans at its original resolution. Methods : A total of 1110 SDOCT volumes (Cirrus, Zeiss, CA) were acquired from both eyes of 624 subjects (139 healthy and 485 glaucomatous patients (POAG)). A convolutional neural network (CNN) consisting of 8 3D-convolutional layers with a total of 600K parameters and was trained using a cross-entropy loss to differentiate between the healthy and glaucomatous scans. To avoid GPU memory constraints, the network was trained using a large model support library that automatically adds swap-in and swap-out nodes for transferring tensors from GPUs to the host and vice versa. This allowed for the OCT scans to be analysed at the original resolution of 200x200x1024. The performance of the network was gauged by computing the area under the receiver operating characteristic (AUC) curve. The performance of this network was also compared to a previously proposed network that ingested downsampled OCT scans (50x50x128), consisted of 5 3D-convolutional layers and had a total of 222K parameters; and a machine-learning technique (random forests) that relied on segmented features (peripapillary nerve fibre thicknesses). Class activation maps (CAM) were also generated for each of these networks to provide a qualitative view of the regions that the network deemed as important and relevant to the task. Results : The AUCs computed on the test set for the networks that analysed the volumes at the original and downsampled resolutions was found to be 0.92 and 0.91, respectively. The CAMs obtained using the high resolution images show more detail in comparison to the downsampled volume. The random forest technique showed an AUC of 0.85. Conclusions : The performance of the two networks was comparable for glaucoma detection but showed a vast improvement over the random forest that relied on segmented features. The ability to retain detail (as shown in the CAM) will likely allow for improvements in other tasks, such as spatial correspondences between visual field test locations and retinal structure

Purpose : Optical coherence tomography (OCT) two dimensional (2D) ganglion cell inner plexiform layer (GCIPL) thickness maps often reveal subtle abnormalities that might be washed out with summarized parameters (global or sectoral measurements). Also, the spatial pattern of GCIPL shows useful information to understand the extent and magnitude of localized damages. The purpose of this study was to predict next-visit 2D GCIPL thickness map based on the current and past GCIPL thickness maps. Methods : 346 glaucomatous eyes (191 subjects) with at least 5 visits with OCT tests were included in the study. GCIPL thickness maps were obtained using a clinical OCT (Cirrus HD-OCT, Zeiss, Dublin, CA; software version 9.5.1.13585; 200x200 macular cube scan). Since 83.2% of subjects were stable (average GCIPL change < 2um per year), we simulated progressing cases for diffuse damage pattern and hemifield damage pattern (superior vs. inferior hemifield damage was 50:50) (Figure 1 (c) and (d)). A deep learning based method, time-aware convolutional long short-term memory (TC-LSTM), was developed to handle irregular time intervals of longitudinal GCIPL thickness maps and predict the 5th GCIPL thickness map from the past 4 tests. The TC-LSTM model was compared with a conventional linear regression (LR) analysis. Mean square error (MSE, normalized to pixel intensity) and peak signal to noise ratio (PSNR) between predicted maps and ground truth maps were used to quantify the prediction quality (lower MSE and higher PSNR indicate better results). The Wilcoxon signed-rank test was used to compare TC-LSTM results and LR results. Results : TC-LSTM achieved lower MSE and higher PSNR compared to the LR model (MSE 0.00049 vs. 0.00061, p<0.001, and PSNR 34.45 vs. 32.52 dB, p=0.035). Subjective evaluation by 3 expert ophthalmologists showed that TC-LSTM model had closer representations of the ground truth maps than the LR model (Table 1, Figure 1). Conclusions : The next visit GCIPL thickness maps were successfully generated using TC-LSTM with higher accuracy compared to LR model both quantitatively and subjectively

Purpose : In mild glaucoma, RNFL thinning and visual field (VF) loss are often localized, but structure-function modeling is impeded by variability due to individual eye anatomy. We perform high-resolution spatial correlations of RNFLT maps for each VF location to identify relevant areas and study further improvements by geometrically aligning RNFLT maps based on artery trajectories. Methods : In 419 SITA Standard 24-2 Humphrey VFs with at most mild glaucoma (mean deviation >=-3dB) with accompanying circumpapillary Cirrus HD-OCT RNFLT maps, we computed pixel-wise correlations (52 VF locations x 40401 pixels). We then performed an alignment operation, ensuring that the two major retinal arteries follow the same lines in all scans. We piecewise linearly approximated the trajectories of the arteries on 4 concentric circles around ONH (Fig. 1a), determined the necessary rotation for each pixel, and morphed the images accordingly (Fig. 1b). Results : For the pre-alignment RNFLT (correlation maps Fig. 2 top) we observed: (1) relatively high correlations (max 0.29); (2) most of the high-correlation regions are highly localized around the median trajectories of the major arteries at most VF locations, possibly due to the stacked character of the fiber bundles close to ONH, which impedes precise spatial mapping to the VF. This observation suggests general retinal vulnerability zones rather than highly VF location-specific areas as assumed by many previous structure-function models. Accordingly, morphing the RNFLT maps by aligning the eyespecific artery locations increased the maximal correlations on 25 of the 52 VF locations (Fig. 2 bottom, marked in green), particularly in nasal and inferior VF, with improvements of up to 0.1 (inferior arcuate region of VF). At many locations, aligned vulnerability areas become substantially more conspicuous (e.g. the location enlarged on the top left) and might have been missed without aligning. Conclusions : High-resolution structure-function correlations reveal retinal vulnerability zones in mild glaucoma. At many VF locations, these zones become better correlated with VF regions when RNFLT maps are aligned along the arteries. Specific attention to RNFL thinning in these zones in glaucoma suspects may improve the detection of initial VF loss glaucoma

Observational studies in glaucoma patients can provide important evidence on treatment effects, especially for combination therapies which are often used in reality. But the success relies on the reduction of selection bias through methods such as propensity score (PS) weighting. The objective of this study was to assess the effects of five glaucoma treatments (medication, laser, non-laser surgery (NLS), laser + medication, and NLS + medication) on 1-year intraocular pressure (IOP) change. Data were collected from 90 glaucoma subjects who underwent a single laser, or NLS intervention, and/or took the same medication for at least 6 months, and had IOP measures before the treatment and 12-months after. Baseline IOP was significantly different across groups (p = 0.007) and this unbalance was successfully corrected by the PS weighting (p = 0.81). All groups showed statistically significant PS-weighted IOP reductions, with the largest reduction in NLS group (-6.78 mmHg). Baseline IOP significantly interacted with treatments (p = 0.03), and at high baseline IOP medication was less effective than other treatments. Our findings showed that the 1-year IOP reduction differed across treatment groups and was dependent on baseline IOP. The use of PS-weighted methods reduced treatment selection bias at baseline and allowed valid assessment of the treatment effect in an observational study.

Glaucoma is the world's leading cause of irreversible blindness, and falls are a major public health concern in glaucoma patients. Although recent evidence suggests the involvements of the brain toward advanced glaucoma stages, the early brain changes and their clinical and behavioral consequences remain poorly described. This study aims to determine how glaucoma may impair the brain structurally and functionally within and beyond the visual pathway in the early stages, and whether these changes can explain visuomotor impairments in glaucoma. Using multi-parametric magnetic resonance imaging, glaucoma patients presented compromised white matter integrity along the central visual pathway and around the supramarginal gyrus, as well as reduced functional connectivity between the supramarginal gyrus and the visual occipital and superior sensorimotor areas when compared to healthy controls. Furthermore, decreased functional connectivity between the supramarginal gyrus and the visual brain network may negatively impact postural control measured with dynamic posturography in glaucoma patients. Taken together, this study demonstrates that widespread structural and functional brain reorganization is taking place in areas associated with visuomotor coordination in early glaucoma. These results implicate an important central mechanism by which glaucoma patients may be susceptible to visual impairments and increased risk of falls.

Importance/UNASSIGNED:Genetic variants associated with primary open-angle glaucoma (POAG) are known to influence disease risk. However, the clinical effect of associated variants individually or in aggregate is not known. Genetic risk scores (GRS) examine the cumulative genetic load by combining individual genetic variants into a single measure, which is assumed to have a larger effect and increased power to detect relevant disease-related associations. Objective/UNASSIGNED:To investigate if a GRS that comprised 12 POAG genetic risk variants is associated with age at disease diagnosis. Design, Setting, and Participants/UNASSIGNED:A cross-sectional study included individuals with POAG and controls from the Glaucoma Genes and Environment (GLAUGEN) study and the National Eye Institute Glaucoma Human Genetics Collaboration (NEIGHBOR) study. A GRS was formulated using 12 variants known to be associated with POAG, and the alleles associated with increasing risk of POAG were aligned in the case-control sets. In case-only analyses, the association of the GRS with age at diagnosis was analyzed as an estimate of disease onset. Results from cohort-specific analyses were combined with meta-analysis. Data collection started in August 2012 for the NEIGHBOR cohort and in July 2008 for the GLAUGEN cohort and were analyzed starting in March 2018. Main Outcomes and Measures/UNASSIGNED:Association of a 12 single-nucleotide polymorphism POAG GRS with age at diagnosis in individuals with POAG using linear regression. Results/UNASSIGNED:The GLAUGEN study included 976 individuals with POAG and 1140 controls. The NEIGHBOR study included 2132 individuals with POAG and 2290 controls. For individuals with POAG, the mean (SD) age at diagnosis was 63.6 (9.8) years in the GLAUGEN cohort and 66.0 (13.7) years in the NEIGHBOR cohort. For controls, the mean (SD) age at enrollment was 65.5 (9.2) years in the GLAUGEN cohort and 68.9 (11.4) years in the NEIGHBOR cohort. All study participants were European white. The GRS was strongly associated with POAG risk in case-control analysis (odds ratio per 1-point increase in score = 1.24; 95% CI, 1.21-1.27; P = 3.4 × 10-66). In case-only analyses, each higher GRS unit was associated with a 0.36-year earlier age at diagnosis (β = -0.36; 95% CI, -0.56 to -0.16; P = 4.0 × 10-4). Individuals in the top 5% of the GRS had a mean (SD) age at diagnosis of 5.2 (12.8) years earlier than those in the bottom 5% GRS (61.4 [12.7] vs 66.6 [12.9] years; P = 5.0 × 10-4). Conclusions and Relevance/UNASSIGNED:A higher dose of POAG risk alleles was associated with an earlier age at glaucoma diagnosis. On average, individuals with POAG with the highest GRS had 5.2-year earlier age at diagnosis of disease. These results suggest that a GRS that comprised genetic variants associated with POAG could help identify patients with risk of earlier disease onset impacting screening and therapeutic strategies.

Purpose : OCT Angiography (OCTA) can be used to measure retinal vessel density (VD). These scans can be of various sizes and may be centered on the optic nerve head (ONH) or macula. In this study, we examined the glaucoma discrimination performance of VD using different scanning sizes and locations and compared it with the performance of conventional structural and functional biomarkers to identify the best glaucoma discrimination scanning protocol. Methods : 79 healthy and glaucomatous eyes (50 subjects) were included in the study. Subjects with diabetes, vascular disease, or who were using medications known to affect retinal thickness were excluded. 3x3 and 6x6mm ONH and macula OCTA images were obtained using Cirrus HD-OCT Angioplex (Zeiss, Dublin, CA). Global and sectoral VD was calculated using native software on the device. Area under the receiver operating characteristics (AUC) was used to determine the discrimination ability of VD, retinal nerve fiber layer (RNFL) thickness, rim area, cup-to-disc (C/D) ratio, ganglion cell inner plexiform layer (GCIPL) thickness, and visual field mean deviation (MD). Bootstrapping was used for comparison between the AUCs. Results : Subjects with glaucoma had statistically significantly different measurements than healthy individuals for all tested parameters except for the majority of macula VD (both 3x3 and 6x6 scanning sizes; Table). VD measurements that had the best glaucoma discrimination ability were acquired from the ONH from all sectors of the 3x3 scans and in the outer and full sectors in the 6x6 scans (Table). For these ONH parameters, no significant difference was detected from the best discriminating parameter (average RNFL and rim area). All macula VD measurements had significantly worse discrimination performance. Conclusions : Among VD scanning options, the ONH scans are the most suitable for glaucoma discrimination. However, the coarse sampling in the larger scan (6x6mm) reduces this capability inside and immediately adjacent to the ONH

Purpose : To examine the effect of co-variables commonly used in ocular structure models on ocular vessel density (VD) measurements provided by OCT angiography (OCTA) Methods : Healthy subjects with a normal comprehensive ophthalmic examination, axial length (AL) measurements, qualified visual fields (VF; Humphrey Field Analyzer; Zeiss, Dublin, CA), and optic nerve head (ONH) and macula OCT and OCTA scans (Cirrus HD-OCT 200x200 cube scans and 3x3 mm/ 6x6 mm Angioplex; Zeiss) were included. Subjects with comorbidities affecting the systemic or local micro or macro vasculature and subjects taking medications that modify vessel diameter were excluded. Peripapillary, ONH, and macular VD were calculated using the device's native software. Mixed-effects models were used accounting for age, gender, signal strength, AL, and inter- and intra-subject correlation. Results : 72 eyes (46 subjects) with a mean age of 45.1 (+/-13.9) years, mean AL of 23.82 (+/-1.03) mm, and mean signal strength of 8.32 (+/-1.04) were included in the study for ONH analysis and a subset of 33 eyes were included for macular analysis. The 3x3 and 6x6 ONH inner VD measurements decrease as age advances (-0.1 +/-0.02 mm/mm2, p=0.005; -0.07 +/-0.02 mm/mm2, p=0.0026, respectively). The central and inner measurements in the 3x3 macular scans decrease with age (-0.14 +/-0.03 mm/mm2, p=0.0006; -0.06 +/-0.01mm/mm2, p=0.0003, respectively). ONH and macula VD in both scanning sizes were not associated with AL, except for the macula 6x6 outer region (0.41 +/-0.05 mm/mm2, p=0.05). Only macular VD measurements were associated with signal strength. Conclusions : When analyzing ocular VD, the variables of age, AL, and image quality, should be considered

Purpose : To examine the effect of varying levels of intraocular (IOP) and intracranial pressure (ICP) on the reproducibility of lamina cribrosa (LC) microstructure measurements. Methods : Spectral-domain OCT scans of the optic nerve head (ONH) were obtained from adult healthy rhesus macaque monkeys while IOP and ICP were changed in a controlled environment. Gravity-based perfusion through a needle inserted into the anterior chamber controlled IOP (low, medium, high settings). Perfusion through the lateral ventricle controlled ICP (low, high settings). Scans were registered in 3D and LC microstructure measurements (beam thickness, pore diameter) were calculated from shared regions among scans acquired at each setting using a previously described segmentation algorithm. Microstructure measurement results were used to calculate the beam/pore ratio of each scan, and a 2-way ANOVA test compared the effect of different IOP and ICP settings on measurement reproducibility. Results : The results of 2 eyes were analyzed. For average beam thickness IOP had a significant effect on measurement reproducibility but ICP did not (p=0.005, p=0.66, respectively). For average pore diameter IOP also had a significant effect on measurement reproducibility but ICP did not (p=0.009, p=0.97, respectively). The effect of IOP and ICP on beam/pore ratio reproducibility was not significant (p=0.23, p=0.80, respectively). Results are summarized in Figure 1. Conclusions : Our study provides evidence that beam/pore ratio measurements are reproducible regardless of acquisition at different IOP and ICP settings. This parameter is less influenced by scanning angle and image quality than other measurements. This information supports direct comparison of beam/pore ratio measurements obtained in varying pressure settings