Spectral Domain Optical Coherence Tomography Assessment of Macular and Optic Nerve Alterations in Patients with Glaucoma and Correlation with Visual Field Index

Inner Retinal Thinning Comparison between Branch Retinal Artery Occlusion and Primary Open-Angle Glaucoma

Purpose: to assess the tomographic retinal layers' thickness in eyes affected by branch retinal artery occlusion (BRAO) and to compare it to those of patients affected by primary open angle glaucoma (POAG). Methods: retrospective review of 27 patients; 16 with BRAO (16 eyes) and 11 with POAG (20 eyes) were identified among those who received SD-OCT scans, including analysis of macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), neuroretinal rim (NRR), circumpapillary RNFL at 3.5 mm and hemisphere asymmetry (HA). Results: the total IPL and INL thinning difference between the two groups was statistically significant (p = 0.0067 and p < 0.0001, respectively). The HA difference for the total macular thinning, mRNFL, GCL, IPL and INL (p < 0.0001) was also statistically significant. The analysis of the average total retinal thinning, total mRNFL and GCL thinning showed no statistically significant difference between the two groups. Conclusions: unilateral inner retinal thinning may represent a sign of temporal BRAO, particularly for INL thinning and HA difference over 17µm in total retinal layer thinning. This information is particularly useful in the diagnosis of previous, undiagnosed BRAO and may help prevent further retinal arterial occlusion and possible cerebrovascular incidents.

Association Between Rate of Ganglion Cell Complex Thinning and Rate of Central Visual Field Loss

Importance

Whether rapid ganglion cell complex (GCC) thinning during an initial follow-up period is associated with rates of central visual field loss over time is unclear but important to understand because risk of glaucoma progression can help guide treatment intensity.

Objective

To investigate the association between the rate of GCC thinning during initial follow-up and the rate of central visual field loss.

Design, Setting, and Participants

This retrospective cohort study assessed patients older than 18 years with glaucoma at a tertiary glaucoma center who were followed up from June 18, 2014, to January 11, 2019. Data analysis for the current study was undertaken in March 2022.

Main Outcomes and Measures

Initial rates of GCC thinning were obtained from global GCC thickness values of the first 3 optical coherence tomography (OCT) scans. Rates of central visual field loss were assessed as the change in central (10-2) visual field mean deviation during the 4.7-year follow-up period by univariable and multivariable linear mixed-effects models. Eyes were categorized as slow (>-1 μm/y) or fast (≤-1 μm/y) progressors based on rates of GCC thinning.

Results

The cohort consisted of 202 eyes of 139 patients (mean [SD] age, 68.7 [10.0] years; 72 male [51.8%]); 44 African American patients (31.7%), 13 Asian patients (9.4%), 80 White patients (57.6%), and 2 patients who identified as other race and ethnicity (1.4%) were analyzed. The rate of GCC change was -0.56 μm/y (95% CI, -0.66 to -0.46 μm/y) during a mean initial follow-up of 1.8 years (95% CI, 1.7-2.0 years). A total of 163 eyes (80.7%) were slow OCT progressors, and 39 (19.3%) were fast OCT progressors, with rates of GCC thinning of -0.3 μm/y (95% CI, -0.4 to -0.2 μm/y) and -1.6 μm/y (-1.8 to -1.3 μm/y), respectively. The rates of 10-2 visual field mean deviation worsening among slow and fast OCT progressors were -0.10 dB/y (95% CI, -0.16 to 0.00 dB/y) and -0.34 dB/y (95% CI, -0.51 to -0.16 dB/y), respectively (difference, -0.26 dB/y; 95% CI, -0.45 to -0.07 dB/y; P = .008).

Conclusions and Relevance

In this cohort study, rapid GCC thinning during an initial follow-up period was associated with faster rates of central visual field decline. These findings support use of longitudinal macular OCT scans assisting clinical decision-making for glaucoma and also may guide possible intensification of therapy in high-risk patients.

Ganglion Cell Complex: The Optimal Measure for Detection of Structural Progression in the Macula

PURPOSE

To test the hypothesis that macular ganglion cell complex (GCC) thickness from optical coherence tomography (OCT) provides a stronger change signal regardless of glaucoma severity compared with other macular measures.

DESIGN

Prospective cohort study.

METHODS

Eyes were from 112 patients with moderate to severe glaucoma at baseline from a tertiary glaucoma center. In each 3° × 3° macular superpixel, a hierarchical Bayesian random intercept and slope model with random residual variance was fit to longitudinal full macular thickness (FMT), outer retina layers, GCC, ganglion cell-inner plexiform layer (GCIPL), and ganglion cell layer (GCL) measurements. We estimated population- and individual-level slopes and intercepts. Proportions of substantial worsening and improving superpixel slopes were compared between layers and in superpixels with mild to moderate vs severe damage (total deviation of corresponding visual field location ≥ -8 vs < -8 dB).

RESULTS

Mean (SD) follow-up time and baseline 10-2 visual field mean deviation were 3.6 (0.4) years and -8.9 (5.9) dB, respectively. FMT displayed the highest proportion of significant negative slopes (1932/3519 [54.9%]), followed by GCC (1286/3519 [36.5%]), outer retina layers (1254/3519 [35.6%]), (GCIPL) (1075/3518 [30.6%]), and (GCL) (698/3518 [19.8%]). Inner macular measures detected less worsening in the severe glaucoma group; yet GCC (223/985 [22.6%]) identified the highest proportion (GCIPL: 183/985 [18.6%]; GCL: 106/985 [10.8%]). Proportions of positive rates were small and comparable among all measures.

CONCLUSIONS

GCC is the optimal macular measure for detection of structural change in eyes with moderate to severe glaucoma. Although a higher proportion of worsening superpixels was observed for FMT, a large portion of FMT change could be attributed to changes in outer retina layers.

Impact of Epiretinal Membrane on Optical Coherence Tomography Tools Used for Monitoring Glaucoma

Background: Retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) measurements can be influenced by many factors including the presence of concomitant retinal diseases. The aim of this study it to assess the impact of epiretinal membrane (ERM) on RNFL and GCL assessment using optical coherence tomography (OCT). Methods: GCL, peripapillary RNFL (pRNFL), and Bruch’s Membrane Opening Minimum Rim Width (BMO-MRW) thicknesses were analysed using an SD-OCT (Spectralis OCT) in eyes with idiopathic ERM and compared with a control group. Results: 161 eyes were included, 73 eyes in the control group and 88 eyes with idiopathic ERM. The pRNFL analysis revealed a statistically significant difference between the two groups in overall and temporal sector thicknesses. For GCL thickness report, the percentage of scans in which the GCL was erroneously segmented by automatic segmentation was assessed for each eye. A statistically significant difference was found in all sectors (p < 0.001), with the exception of external nasal sector. A statistically significant difference (p < 0.001) in the GCL total volume report was found in ERM group compared to the control group. For MRW at BMO analysis, there was no statistically significant difference in MRW thickness in any sector. Conclusion: In eyes with ERM, the GCL and pRNFL analysis seemed affected by the morphological retinal layers’ modification. MRW-BMO did not appear to be directly affected by the presence of ERM.

Evaluation of putative differences in vessel density and flow area in normal tension and high-pressure glaucoma using OCT-angiography

PURPOSE

To evaluate the putative differences in terms of vessel density and flow area between control (CTRL), high-pressure glaucoma (HPG) and normal tension glaucoma (NTG) subjects at macular and peripapillary level. To assess the correlation between Visual Field Index (VFI), the stage of glaucoma, and optical coherence tomography angiography (OCT-A) parameters.

MATERIAL AND METHODS

In this pilot, prospective study 46 eyes of 46 glaucomatous patients (19 NTG+27 HPG) and 25 control eyes (CTRL) of 25 subjects were recruited. All patients underwent a complete ophthalmologic examination and visual field testing. A 3×3mm volumetric macular scan (Angio Retina [3.0]) and a 4.5×4.5mm diameter peripapillary scan (Angio Disc [4.5]) were performed in the right eye using RTVue-XR Avanti (Optovue, Inc.) OCT-A.

RESULTS

Groups were homogeneous for age (P=0.784) and gender (P=0.623). Among the evaluated optic nerve head (ONH) and macular OCT-A parameters, ONH whole image (P<0.001), inside disc (P=0.021), peripapillary (P<0.001), ONH flow area (P<0.026), macula whole image (P<0.001), fovea (P<0.001), parafovea (P<0.001) showed a significant difference when CTRL group was compared to HPG group at the post hoc test. Similarly, ONH whole image (P<0.001), inside disc (P=0.005), peripapillary (P<0.001), ONH flow area (P<0.026), macula whole image (P<0.001), FOVEA (P<0.001), parafovea (P<0.001) showed a significant difference were CTRL were compared to NTG group. On the contrary, no significant difference was found when NTG and HPG groups were compared. Age was not significantly correlated with any of the OCT-A parameters. The stage of the disease showed a high, significant, correlation with ONH whole image (r=-0.81; P<0.0001), inside disc (r=-0.42; P<0.0001), peripapillary (r=-0.81; P<0.0001), RNFL (r=-0.79; P<0.0001), macula whole image (r=0.56; P<0.0001), fovea (r=-0.78; P<0.0001) and parafovea (r=0.67; P<0.0001). On the contrary, VFI showed a high, significant, correlation with ONH whole image (r=0.77; P<0.0001), inside disc (r=0.39; P=0.0018), peripapillary (r=0.713; P<0.0001), RNFL (r=0.63; P<0.0001), macula whole image (r=-0.39; P=0.0007), fovea (r=0.60; P<0.0001) and parafovea (r=-0.52; P<0.0001).

CONCLUSIONS

Our data support the usefulness of the OCT-A in the common clinical practice for diagnosis, staging, evaluating the progression of the disease as well as for better understanding of its pathogenic mechanisms.

Subclinical Signs of Retinal Involvement in Hereditary Angioedema

To explore retinal abnormalities using spectral domain optical coherence tomography (SD-OCT) and OCT-angiography (OCT-A) in a highly selective cohort of patients with type I hereditary angioedema (HAE). This prospective case-control study included 40 type I HAE patients and 40 age-/sex-matched healthy subjects (HC). All participants underwent SD-OCT-scanning of retinal posterior pole (PP), peripapillary retinal nerve fiber layer (pRNFL), and optic nerve head (ONH). Superficial/deep capillary density was analyzed by OCT-A. A total of 80 eyes from 40 HAE and 40 eyes from HC were evaluated. The pRNFL was thicker in HAE than in HC in nasal superior (p < 0.0001) and temporal quadrants (p = 0.0005 left, p = 0.003 right). The ONH thickness in HAE patients was greater than in HC in the nasal (p = 0.008 left, p = 0.01 right), temporal (p = 0.0005 left, p = 0.003 right), temporal inferior (p = 0.007 left, p = 0.0008 right), and global (p = 0.005 left, p = 0.007 right) scans. Compared to HC, HAE showed a lower capillary density in both superficial (p = 0.001 left, p = 0.006 right) and deep (p = 0.008 left, p = 0.004 right) whole images, and superficial (p = 0.03 left) and deep parafoveal (p = 0.007 left, p = 0.005 right) areas. Our findings documented subclinical retinal abnormalities in type I HAE, supporting a potential role of the retinal assessment by SD-OCT/OCT-A as a useful tool in the comprehensive care of HAE patients.

Complex Rearrangement of the Entire Retinal Posterior Pole in Patients with Relapsing Remitting Multiple Sclerosis

There are consolidated data about multiple sclerosis (MS)–dependent retinal neurodegeneration occurring in the optic disk and the macula, although it is unclear whether other retinal regions are affected. Our objective is to evaluate, for the first time, the involvement of the entire retinal posterior pole in patients diagnosed with relapsing remitting multiple sclerosis (RRMS) unaffected by optic neuritis using Spectral Domain–Optical Coherence Tomography (SD–OCT). The study protocol was approved by Tor Vergata Hospital Institutional Ethics Committee (Approval number 107/16), and conforms to the tenets of the Declaration of Helsinki. After a comprehensive neurological and ophthalmological examination, 53 untreated RRMS patients (aged 37.4 ± 10) and 53 matched controls (aged 36.11 ± 12.94) were enrolled. In addition, each patient underwent an examination of the posterior pole using the SD-OCT built-in Spectralis posterior pole scanning protocol. After segmentation, the mean thickness, as well as the thickness of the 64 single regions of interest, were calculated for each retinal layer. No statistically significant difference in terms of average retinal thickness was found between the groups. However, MS patients showed both a significantly thinner ganglion cell layer (p < 0.001), and, although not statistically significant, a thinner inner nuclear layer (p = 0.072) and retinal nerve fiber layer (p = 0.074). In contrast, the retinal pigment epithelium (p = 0.014) and photoreceptor layers p < 0.001) resulted significantly thicker in these patients. Interestingly, the analysis of the region of interest showed that neurodegeneration was non-homogeneously distributed across each layer. This is the first report that suggests a complex rearrangement that affects, layer by layer, the entire retinal posterior pole of RRMS retinas in response to the underlying neurotoxic insult.

Estimating Ganglion Cell Complex Rates of Change With Bayesian Hierarchical Models

Purpose

Develop a hierarchical longitudinal regression model for estimating local rates of change of macular ganglion cell complex (GCC) measurements with optical coherence tomography (OCT).

Methods

We enrolled 112 eyes with four or more macular OCT images and ≥2 years of follow-up. GCC thickness measurements within central 6 × 6 superpixels were extracted from macular volume scans. We fit data from each superpixel separately with several hierarchical Bayesian random-effects models. Models were compared with the Watanabe–Akaike information criterion. For our preferred model, we estimated population and individual slopes and intercepts (baseline thickness) and their correlation.

Results

Mean (SD) follow-up time and median (interquartile range) baseline 24-2 visual field mean deviation were 3.6 (0.4) years and −6.8 (−12.2 to −4.3) dB, respectively. The random intercepts and slopes model with random residual variance was the preferred model. While more individual and population negative slopes were observed in the paracentral and papillomacular superpixels, superpixels in the superotemporal and inferior regions displayed the highest correlation between baseline thickness and rates of change (r = –0.43 to –0.50 for the top five correlations).

Conclusions

A Bayesian linear hierarchical model with random intercepts/slopes and random variances is an optimal initial model for estimating GCC slopes at population and individual levels. This novel model is an efficient method for estimating macular rates of change and probability of glaucoma progression locally.

Translational Relevance

The proposed Bayesian hierarchical model can be applied to various macular outcomes from different OCT devices and to superpixels of variable sizes to estimate local rates of change and progression probability.

Macular imaging with optical coherence tomography in glaucoma

With the advent of spectral-domain optical coherence tomography, imaging of the posterior segment of the eye can be carried out rapidly at multiple anatomical locations, including the optic nerve head, circumpapillary retinal nerve fiber layer, and macula. There is now ample evidence to support the role of spectral-domain optical coherence tomography imaging of the macula for detection of early glaucoma. Macular spectral-domain optical coherence tomography measurements demonstrate high reproducibility, and evidence on its utility for detection of glaucoma progression is accumulating. We present a comprehensive review of macular spectral-domain optical coherence tomography imaging emerging as an essential diagnostic tool in glaucoma.

Diffusional Kurtosis Imaging of White Matter Degeneration in Glaucoma

Glaucoma is an optic neuropathy characterized by death of retinal ganglion cells and loss of their axons, progressively leading to blindness. Recently, glaucoma has been conceptualized as a more diffuse neurodegenerative disorder involving the optic nerve and also the entire brain. Consistently, previous studies have used a variety of magnetic resonance imaging (MRI) techniques and described widespread changes in the grey and white matter of patients. Diffusion kurtosis imaging (DKI) provides additional information as compared with diffusion tensor imaging (DTI), and consistently provides higher sensitivity to early microstructural white matter modification. In this study, we employ DKI to evaluate differences among healthy controls and a mixed population of primary open angle glaucoma patients ranging from stage I to V according to Hodapp–Parrish–Anderson visual field impairment classification. To this end, a cohort of patients affected by primary open angle glaucoma (n = 23) and a group of healthy volunteers (n = 15) were prospectively enrolled and underwent an ophthalmological evaluation followed by magnetic resonance imaging (MRI) using a 3T MR scanner. After estimating both DTI indices, whole-brain, voxel-wise statistical comparisons were performed in white matter using Tract-Based Spatial Statistics (TBSS). We found widespread differences in several white matter tracts in patients with glaucoma relative to controls in several metrics (mean kurtosis, kurtosis anisotropy, radial kurtosis, and fractional anisotropy) which involved localization well beyond the visual pathways, and involved cognitive, motor, face recognition, and orientation functions amongst others. Our findings lend further support to a causal brain involvement in glaucoma and offer alternative explanations for a number of multidomain impairments often observed in glaucoma patients.

Reorganization of the structural connectome in primary open angle Glaucoma

Primary open angle Glaucoma (POAG) is one of the most common causes of permanent blindness in the world. Recent studies have suggested the hypothesis that POAG is also a central nervous system disorder which may result in additional (i.e., extra-ocular) involvement. The aim of this study is to assess possible structural, whole-brain connectivity alterations in POAG patients. We evaluated 23 POAG patients and 15 healthy controls by combining multi-shell diffusion weighted imaging, multi-shell, multi-tissue probabilistic tractography, graph theoretical measures and a recently designed 'disruption index', which evaluates the global reorganization of brain networks. We also studied the associations between the whole-brain structural connectivity measures and indices of visual acuity including the field index (VFI) and two Optical Coherence Tomography (OCT) parameters, namely the Macula Ganglion Cell Layer (MaculaGCL) and Retinal Nerve Fiber Layer (RNFL) thicknesses. We found both global and local structural connectivity differences between POAG patients and controls, which extended well beyond the primary visual pathway and were localized in the left calcarine gyrus (clustering coefficient p = 0.036), left lateral occipital cortex (clustering coefficient p = 0.017, local efficiency p = 0.035), right lingual gyrus (clustering coefficient p = 0.009), and right paracentral lobule (clustering coefficient p = 0.009, local efficiency p = 0.018). Group-wise (clustering coefficient, p = 6.59∙10-7 and local efficiency p = 6.23·10-8) and subject-wise disruption indices (clustering coefficient, p = 0.018 and local efficiency, p = 0.01) also differed between POAG patients and controls. In addition, we found negative associations between RNFL thickness and local measures (clustering coefficient, local efficiency and strength) in the right amygdala (local efficiency p = 0.008, local strength p = 0.016), right inferior temporal gyrus (clustering coefficient p = 0.036, local efficiency p = 0.042), and right temporal pole (local strength p = 0.008). Overall, we show, in patients with POAG, a whole-brain structural reorganization that spans across a variety of brain regions involved in visual processing, motor control, and emotional/cognitive functions. We also identified a pattern of brain structural changes in relation to POAG clinical severity. Taken together, our findings support the hypothesis that the reduction in visual acuity from POAG can be driven by a combination of local (i.e., in the eye) and more extended (i.e., brain) effects.

Brain networks reorganization and functional disability in glaucoma

Glaucoma is an optic neuropathy characterized by progressive loss of retinal ganglion cells with associated structural and functional changes of the optic nerve head and retinal nerve fiber layer. However, recent studies employing advanced neuroimaging techniques confirmed that glaucomatous damage is not limited to the eye but extends to the brain, affecting it also beyond the central visual pathways and disrupting brain network organization. We therefore posit that, while visual field changes play an important role in glaucoma-induced disability, central nervous pathways and mechanisms may play an important role in sustaining functional and daily living disability caused by the disease. Here we to summarize the current state of the art on the involvement of central brain circuits and possibly related disabilities in patients with glaucoma.

Primary Open Angle Glaucoma Is Associated With Functional Brain Network Reorganization

Background: Resting-state functional magnetic resonance imaging (rs-fMRI) is commonly employed to study changes in functional brain connectivity. The recent hypothesis of a brain involvement in primary open angle Glaucoma has sprung interest for neuroimaging studies in this classically ophthalmological pathology.

Object: We explored a putative reorganization of functional brain networks in Glaucomatous patients, and evaluated the potential of functional network disruption indices as biomarkers of disease severity in terms of their relationship to clinical variables as well as select retinal layer thicknesses.

Methods: Nineteen Glaucoma patients and 16 healthy control subjects (age: 50–76, mean 61.0 ± 8.2 years) underwent rs-fMRI examination at 3T. After preprocessing, rs-fMRI time series were parcellated into 116 regions using the Automated Anatomical Labeling atlas and adjacency matrices were computed based on partial correlations. Graph-theoretical measures of integration, segregation and centrality as well as group-wise and subject-wise disruption index estimates (which use regression of graph-theoretical metrics across subjects to quantify overall network changes) were then generated for all subjects. All subjects also underwent Optical Coherence Tomography (OCT) and visual field index (VFI) quantification. We then examined associations between brain network measures and VFI, as well as thickness of retinal nerve fiber layer (RNFL) and macular ganglion cell layer (MaculaGCL).

Results: In Glaucoma, group-wise disruption indices were negative for all graph theoretical metrics. Also, we found statistically significant group-wise differences in subject-wise disruption indexes in all local metrics. Two brain regions serving as hubs in healthy controls were not present in the Glaucoma group. Instead, three hub regions were present in Glaucoma patients but not in controls. We found significant associations between all disruption indices and VFI, RNFL as well as MaculaGCL. The disruption index based on the clustering coefficient yielded the best discriminative power for differentiating Glaucoma patients from healthy controls [Area Under the ROC curve (AUC) 0.91, sensitivity, 100%; specificity, 78.95%].

Conclusions: Our findings support a possible relationship between functional brain changes and disease severity in Glaucoma, as well as alternative explanations for motor and cognitive symptoms in Glaucoma, possibly pointing toward an inclusion of this pathology in the heterogeneous group of disconnection syndromes.