Macular Impairment in Fabry Disease: A Morpho-functional Assessment by Swept-Source OCT Angiography and Focal Electroretinography

SD-OCT Imaging of Macular Changes in Fabry Disease: A Case Report

Fabry disease (FD) is a rare, X-linked lysosomal storage disorder that can result in fatal end-stage renal disease, heart failure, and cerebro-occlusive events. Vague clinical symptoms and rarity often mean diagnosis and potential treatment is delayed. Ophthalmic findings in FD patients can be helpful in establishing an early diagnosis and timely treatment. Spectral domain optical coherence tomography (SD-OCT) imaging in FD patients shows hyper-reflective foci (HRF) in characteristic patterns within the inner retinal layers. We found that the HRF was localised in linear distributions at the deep and superficial borders of the retinal inner nuclear layer, likely reflecting anatomic vascular plexuses and FD-related sphingolipid deposition within the vessel walls. These results highlight the potential use of SD-OCT in FD and how it may aid diagnosis in undifferentiated patients, prognostication, and disease monitoring.

Correlation of retinal vascular characteristics with laboratory and ocular findings in Fabry disease: exploring ocular diagnostic biomarkers

BACKGROUND

The goal of this study was to evaluate macular microvascular changes in patients with Fabry disease (FD) using optical coherence tomography angiography (OCTA) and to explore their correlation with laboratory and ocular findings.

METHODS

A total of 76 eyes (38 patients) and 48 eyes of 24 healthy controls were enrolled in this prospective study. Vessel Area Density (VAD) and Foveal Avascular Zone (FAZ) area were calculated on 2.9 × 2.9 mm OCTA images scanned with the Heidelberg Spectralis II (Heidelberg, Germany). VAD was measured in three layers: Superficial Vascular Plexus (SVP), Intermediate Capillary Plexus (ICP), and Deep Capillary Plexus (DCP). All scans were analyzed with the EA-Tool (Version 1.0), which was coded in MATLAB (The MathWorks Inc, R2017b). FAZ area was manually measured in full-thickness, SVP, ICP and DCP scans.

RESULTS

Average VAD in SVP, ICP and DCP was higher in Fabry disease patients than in controls (49.4 ± 11.0 vs. 26.5 ± 6.2, 29.6 ± 7.4 vs. 20.2 ± 4.4, 32.3 ± 8.8 vs. 21.7 ± 5.1 respectively, p < 0.001). Patients with cornea verticillata (CV) had a higher VAD in ICP and DCP compared to patients without CV (p < 0.01). Patients with increased lysoGb3 concentration had a higher VAD in DCP when compared to patients with normal lysoGb3 concentration (p < 0.04). There was no difference in VAD in patients with and without vascular tortuosity. However, a significantly higher VAD was observed in patients with vascular tortuosity compared to controls (p < 0.03).

CONCLUSIONS

Increased lysoGb3 and VAD in DCP could be reliable biomarkers of disease activity. Cornea verticillata could be adopted as a predictive biomarker for VAD changes and disease progression. The combination of cornea verticillata and increased VAD may serve as a diagnostic biomarker for Fabry disease, however due to the discrepancies in VAD values in various studies, further research has to be done to address this claim.

Investigation of OCTA Biomarkers in Fabry Disease: A Long Term Follow-Up of Macular Vessel Area Density and Foveal Avascular Zone Metrics

INTRODUCTION

Retinal microvasculature is known to be altered in patients with Fabry disease (FD). We aimed to investigate the long-term changes in macular microvasculature and explore a reliable retinal biomarker for treatment monitoring in FD.

METHODS

Prospective study of 26 eyes with FD followed up to 48 months (mean 24, range 8-48). OCT angiography (OCTA) images (2.9 × 2.9 mm) were obtained using Heidelberg Spectralis II at baseline and follow-up. Macular vessel area density (VAD, %) was measured in three layers: superficial vascular plexus (SVP), intermediate capillary plexus (ICP) and deep capillary plexus (DCP) in three peri-macular circular sectors (c1, c2, c3). Additionally, foveal avascular zone (FAZ) area (mm2) and horizontal and vertical diameters (µm) were assessed.

RESULTS

VAD decreased over time in SVP, ICP (in sectors c2 and c3) and DCP (all sectors) (p < 0.04). VAD reduction was predominantly seen in treated FD patients. FAZ and horizontal diameters increased at follow-up in FD patients compared to baseline (p ≤ 0.025). Correlation analysis showed a moderate to strong negative correlation between VAD of SVP and DCP in the innermost circle and FAZ in treated patients (r = - 0.6; p < 0.0001).

CONCLUSIONS

This is the first long-term follow-up OCTA study in FD to our knowledge. A decrease in VAD, pronounced in the peripheral circle and deeper layers, as well as an enlargement of the FAZ could be observed over time. These changes reflect the vascular remodelling during the course of the disease. Interestingly, the reduction of VAD was more pronounced in treated patients. This could be a result of enzyme replacement therapy and could be potentially used as a reliable biomarker for monitoring the treatment of the disease. A baseline examination of VAD and FAZ before treatment initiation is meaningful. Larger studies are needed to establish the use of VAD and FAZ as biomarkers for treatment monitoring.

Ophthalmic Manifestations in Fabry Disease: Updated Review

Fabry disease (FD) is an X-linked lysosomal storage disorder, causing Gb-3 (globotriaosylceramide) buildup in cellular lysosomes throughout the body, in particular in blood vessel walls, neuronal cells, and smooth muscle. The gradual accumulation of this glycosphingolipid in numerous eye tissues causes conjunctival vascular abnormalities, corneal epithelial opacities (cornea verticillata), lens opacities, and retinal vascular abnormalities. Although a severe vision impairment is rare, these abnormalities are diagnostic indicators and prognostics for severity. Cornea verticillata is the most common ophthalmic feature in both hemizygous men and heterozygous females. Vessel tortuosity has been linked to a faster disease progression and may be useful in predicting systemic involvement. New technologies such as optical coherence tomography angiography (OCTA) are useful for monitoring retinal microvasculature alterations in FD patients. Along with OCTA, corneal topographic analysis, confocal microscopy, and electro-functional examinations, contributed to the recognition of ocular abnormalities and have been correlated with systemic involvement. We offer an update regarding FD ocular manifestations, focusing on findings derived from the most recent imaging modalities, to optimize the management of this pathology.

Relationship of Vessel Density to Vessel Length Density in Patients with Treated Fabry Disease

BACKGROUND

Fabry disease (FD) is a potentially lethal lysosomal disorder with systemic vascular changes. Previous studies demonstrated retinal vascular involvement using optical coherence tomography angiography (OCTA) in affected patients; Aim: To analyze and quantify the retinal vasculature measuring vessel density (VD), vessel length density (VLD), and the ratio of VD to VLD (VD/VLD) in superficial capillary plexuses (SCP) and deep capillary plexuses (DCP) using OCTA in patients with FD and to show whether they differ from healthy controls (HC); Patients and methods: Single-center, retrospective, consecutive cohort study of patients with genetically proven FD. Patients underwent an ophthalmological examination including OCTA. VD, VLD, foveal avascular zone (FAZ), and the VD/VLD were compared to an HC group using a linear mixed model; Results: A statistically significant difference in the VLD and VD/VLD of DCP was observed between the two groups (p < 0.001). Using ROC curves with AUC and Youden's Index, a cut-off value for differentiating both groups using VD/VLD in DCP FD with high specificity and high sensitivity was established; Conclusions: FD and HC groups seem to be separable using the VD/VLD ratio in DCP. This new biomarker might differentiate changes in the retinal microvasculature that are not detectable by VD or VLD alone.

Artificial Intelligence for Evaluation of Retinal Vasculopathy in Facioscapulohumeral Dystrophy Using OCT Angiography: A Case Series

Facioscapulohumeral muscular dystrophy (FSHD) is a slowly progressive muscular dystrophy with a wide range of manifestations including retinal vasculopathy. This study aimed to analyse retinal vascular involvement in FSHD patients using fundus photographs and optical coherence tomography-angiography (OCT-A) scans, evaluated through artificial intelligence (AI). Thirty-three patients with a diagnosis of FSHD (mean age 50.4 ± 17.4 years) were retrospectively evaluated and neurological and ophthalmological data were collected. Increased tortuosity of the retinal arteries was qualitatively observed in 77% of the included eyes. The tortuosity index (TI), vessel density (VD), and foveal avascular zone (FAZ) area were calculated by processing OCT-A images through AI. The TI of the superficial capillary plexus (SCP) was increased (p < 0.001), while the TI of the deep capillary plexus (DCP) was decreased in FSHD patients in comparison to controls (p = 0.05). VD scores for both the SCP and the DCP results increased in FSHD patients (p = 0.0001 and p = 0.0004, respectively). With increasing age, VD and the total number of vascular branches showed a decrease (p = 0.008 and p < 0.001, respectively) in the SCP. A moderate correlation between VD and EcoRI fragment length was identified as well (r = 0.35, p = 0.048). For the DCP, a decreased FAZ area was found in FSHD patients in comparison to controls (t (53) = -6.89, p = 0.01). A better understanding of retinal vasculopathy through OCT-A can support some hypotheses on the disease pathogenesis and provide quantitative parameters potentially useful as disease biomarkers. In addition, our study validated the application of a complex toolchain of AI using both ImageJ and Matlab to OCT-A angiograms.

Frequency Doubling Technology Visual Field Loss in Fabry Subjects Related to Retinal Ganglion Cell Function as Explored by ERG and OSOME

Purpose

This study aims to evaluate potential causes of FDT visual field loss in a selected group of Fabry subjects.

Patients and Methods

This is a pilot observational study. Subjects were assessed during 2 visits. The following tests were performed: visual acuity, tonometry, optical coherence tomography (OCT) optic nerve scan, frequency doubling time (FDT) and threshold (SAP) VF, ERG, and Online Spectro-reflectometry Oxygenation Measurement in the Eye (OSOME). Results are compared across visits and, when indicated, interpreted against those collected on non-Fabry population matched for age and sex.

Results

The study population was composed of 3 males (34.3 ± 8.9 y.o.) and 5 females (46.4 ± 6.5 y.o). For all subjects, BCVA remained 6/6 OU throughout the study and OCT optic nerve scans were normal. FDT showed a defect in at least 1 quadrant for all participants, in contrast with SAP. FDT PSD value was found different vs SAP. For ERG, the i-wave (52.1 + 2.7 ms) and B-waves (31.6 ± 2.1 ms) peak times were significantly longer compared to a non-Fabry population (p < 0.05). Overall blood oxygenation varied from 61.3% ± 4% to 68.1% ± 4% at the second visit, suggesting a loss of capillary perfusion. Blood volume varied based on location (superior/inferior), eye tested (OD/OS) and time (visit 1/2). The range of values exceeds normal subjects findings (p < 0.05). Blood volume was correlated to FDT PSD value for the superior area of the optic nerve.

Conclusion

The results suggest that Fabry subjects present FDT deficits and abnormal ERG patterns that may be explained by a retinal dysfunction affecting retinal ganglion cells (RGCs), second to vascular alterations.

Radial Peripapillary Capillary Plexus Perfusion and Endothelial Dysfunction in Early Post-SARS-CoV-2 Infection

Background: Endothelial cells damage and thromboinflammation are considered key elements in the generation of organ impairment in patients with COVID-19 disease. The endothelial function is evaluated by measuring flow-mediated dilation (FMD). We aimed to analyze the association between FMD impairment and retinal vascular parameters in early post-COVID-19 patients. 00118-00199Tomography (OCT), OCT Angiography (OCTA) and slit lamp examination were performed. FMD ≤ 7% was considered as pathological. Our primary outcome was to assess potential differences in the radial peripapillary capillary plexus flow index (RPCP-FI) and RPCP density (RPCP-D) values between post-COVID-19 patients with and without FMD impairment. The associations of other retinal vascular parameters with FMD impairment were assessed as secondary endpoints. Results: FMD impairment was detected in 31 patients (37.8%). RPCP-FI (p = 0.047), age (p = 0.048) and prevalence of diabetes (p = 0.046) significantly differed in patients with FMD ≤ 7% in regression analysis. RPCP-FI was linearly correlated with FMD values (R = 0.244, p =0.027). SCT was found to be lower in patients with impaired FMD (p = 0.004), although this difference was only a trend in binary logistic regression output (p = 0.07). Conclusions: Early post-COVID-19 patients showed a higher prevalence of FMD impairment compared to the general population. Age, diabetes and RPCP-FI were independently correlated with the presence of endothelial impairment in the early post-infective period.

Retinal biomarkers of Cerebral Small Vessel Disease: A systematic review

INTRODUCTION

Cerebral Small Vessel Disease (CSVD), a progressive degenerative disorder of small caliber cerebral vessels, represents a major contributor to stroke and vascular dementia incidence worldwide. We sought to conduct a systematic review of the role of retinal biomarkers in diagnosis and characterization of CSVD.

METHODS

We conducted a systematic review of MEDLINE, PubMed, Scopus, the Cochrane Library Database, and Web of Science. We identified studies of sporadic CSVD (including CSVD not otherwise specified, Cerebral Amyloid Angiopathy, and Hypertensive Arteriopathy) and the most common familial CSVD disorders (including CADASIL, Fabry disease, and MELAS). Included studies used one or more of the following tools: visual fields assessment, fundus photography, Optical Coherence Tomography and OCT Angiography, Fluorescein Angiography, Electroretinography, and Visual Evoked Potentials.

RESULTS

We identified 48 studies of retinal biomarkers in CSVD, including 9147 cases and 12276 controls. Abnormalities in retinal vessel diameter (11 reports, n = 11391 participants), increased retinal vessel tortuosity (11 reports, n = 617 participants), decreased vessel fractal dimension (5 reports, n = 1597 participants) and decreased retinal nerve fiber layer thickness (5 reports, n = 4509 participants) were the biomarkers most frequently associated with CSVD. We identified no reports conducting longitudinal retinal evaluations of CSVD, or systematically evaluating diagnostic performance.

CONCLUSION

Multiple retinal biomarkers were associated with CSVD or its validated neuroimaging biomarkers. However, existing evidence is limited by several shortcomings, chiefly small sample size and unstandardized approaches to both biomarkers' capture and CSVD characterization. Additional larger studies will be required to definitively determine whether retinal biomarkers could be successfully incorporated in future research efforts and clinical practice.

Vascular and structural analyses of retinal and choroidal alterations in Fabry disease: the effect of hyperreflective foci and retinal vascular tortuosity

PURPOSE

To evaluate the effects of Fabry disease (FD) on the retinal microvasculature and choroidal vascular and structural characteristics.

METHODS

This study included 10 patients with FD and 10 age-matched healthy controls. Binarized enhanced depth imaging optical coherence tomography (OCT) images were used to measure the total choroidal area, luminal area, and stromal area with ImageJ software. The choroidal vascularity index (CVI) was assessed. The vessel densities (VD) of the retinal capillary plexuses and foveal avascular zone (FAZ) area were measured with OCT-angiography.

RESULTS

The most common anterior segment finding was cornea verticillata (60.0%) and the most frequent posterior segment finding was vascular tortuosity (50.0%). Intraretinal hyperreflective foci on B-scan OCT was observed in 50.0% of the cases. In Fabry cases, a linear mixed model with random intercept revealed that 1% change in CVI was related to -0.009 mm² (p = .015) change in FAZ area and -0.047 mm change, (p = .024) in FAZ perimeter. In the presence of retinal vascular tortuosity, 1% change in CVI was related to -0.013 mm² (p = .002) change in FAZ area and -0.052 mm change (p = .004) in FAZ perimeter. In the presence of hyperreflective foci, 1% change in CVI was related to -0.014 mm² (p = .004) change in FAZ area and -0.064 mm change (p = .003) in FAZ perimeter.

CONCLUSION

The significant negative associations between FAZ measurements and CVI suggest a possible interaction between the choroidal and retinal microvasculature of patients with FD. These alterations were more pronounced in the presence of hyperreflective foci and retinal vascular tortuosity.

Retinal vessel tortuosity as a prognostic marker for disease severity in Fabry disease

Purpose

The aim of this case control study was to evaluate the prognostic value of automatically quantified retinal vessel tortuosity from fundus images and vessel density from OCT-A in Fabry disease and to evaluate the correlation of these with systemic disease parameters.

Methods

Automatically quantified perimacular retinal vessel tortuosity (MONA REVA software), acquired by fundus imaging, and perifoveal retinal vessel density, acquired by optic coherence tomography angiography (OCT-A) were compared between 26 FD patients and 26 controls. Gender and FD phenotype were analyzed to the obtained retinovascular data and correlated to the Mainz severity score index (MSSI) and plasma lyso-Gb3.

Results

Automatically quantified retinal vessel tortuosity indices of FD patients were significantly lower, reflecting an increased vessel tortuosity, compared to controls (p = 0.008). Males with a classical phenotype showed significantly lower retinal vessel tortuosity indices compared to males with an oligosymptomatic phenotype and females with a classical or oligosymptomatic phenotype (p < 0.001). The retinal vessel tortuosity index correlated significantly with systemic disease severity parameters [global MSSI (r = − 0.5; p < 0.01), cardiovascular MSSI (r = − 0.5; p < 0.01), lyso-Gb3 (r = − 0.6; p < 0.01)].

Conclusion

We advocate fundus imaging based automatically quantified retinal vessel tortuosity index over OCT-A imaging as it is a quick, non-invasive, easily assessable, objective and reproducible marker.

Tortuosity Index Calculations in Retinal Images: Some Criticalities Arising from Commonly Used Approaches

A growing body of research in retinal imaging is recently considering vascular tortuosity measures or indexes, with definitions and methods mostly derived from cardiovascular research. However, retinal microvasculature has its own peculiarities that must be considered in order to produce reliable measurements. This study analyzed and compared various derived metrics (e.g., TI, TI_avg, TI*CV) across four existing computational workflows. Specifically, the implementation of the models on two critical OCT images highlighted main pitfalls of the methods, which may fail in reliably differentiating a highly tortuous image from a normal one. A tentative, encouraging approach to mitigate the issue on the same OCT exemplificative images is described in the paper, based on the suggested index TI*CV.

Retinal capillary involvement in early post-COVID-19 patients: a healthy controlled study

BACKGROUND

Systemic vascular involvement in COVID-19 has been identified in several patients: not only endothelial derangement and increased permeability are reported to be early hallmarks of organ damage in patients with COVID-19 but are also the most important cause of worsening of clinical conditions in severe cases of SARS-CoV-2 infection. There are several reasons to hypothesize that the eye, and the retina in particular, could be a target of organ damage in SARS-CoV-2 infection.

METHODS

This cohort observational study analyzes OCT angiography and structural OCT of 70 post-COVID-19 patients evaluated at 1-month hospital discharge and 22 healthy control subjects. Primary outcomes were macular vessel density (VD) and vessel perfusion (VP); structural OCT features were evaluated as secondary outcomes. In addition, patients and healthy volunteers were evaluated for best corrected visual acuity, slit lamp photograph, and fundus photo image.

RESULTS

VD and VP in 3 × 3 and 6 × 6 mm scans for SCP and DCP showed no significant differences between the groups. Similarly, CMT and GCL did not reveal significant differences between post-COVID-19 and healthy patients. Nine patients (12.9%) featured retinal cotton wool spots and 10 patients had vitreous fibrillary degeneration. The prevalence of epiretinal membrane and macular hole was similar in the two groups. One case of extra papillary focal retinal hemorrhage was reported in the post-COVID-19 group.

CONCLUSIONS

Macula and perimacular vessel density and perfusion resulted unaltered in mild post-COVID-19 patients at 1-month hospital discharge, suggesting no or minimal retinal vascular involvement by SARS-CoV-2.

Detection of the Microvascular Changes of Diabetic Retinopathy Progression Using Optical Coherence Tomography Angiography

Purpose

To investigate microvascular parameters that are related to the severity of diabetic retinopathy (DR) with optical coherence tomography angiography (OCTA).

Methods

In total, 105 eyes from 105 diabetic patients were recruited in this prospective cross-sectional study, including 37 eyes with no clinical signs of DR (NoDR), 43 eyes with nonproliferative diabetic retinopathy (NPDR), and 25 eyes with proliferative diabetic retinopathy (PDR). Angiogram images from the parafoveal superficial capillary plexus (SCP), the deep capillary plexus (DCP), and the radial peripapillary capillary plexus were analyzed, and metrics were compared among groups. Multivariate regression analysis was used to identify the best OCTA parameters that could distinguish DR severity among groups.

Results

Parafoveal vessel diameter index in the SCP and vessel density (VD) in the DCP showed the strongest correlation with the severity of DR (P < 0.01). Extrafoveal avascular area in the SCP was the parameter that could most distinguish NoDR from NPDR (P < 0.01) with sensitivity and specificity of 83.72% and 78.38%, respectively. VD in the DCP also was the most sensitive biomarker to distinguish NPDR from PDR (P < 0.01) with sensitivity and specificity of 84.00% and 79.07%, respectively.

Conclusions

The microvascular changes in the SCP and DCP in DR may have different characteristics that could be identified with specific OCTA parameters. OCTA serves as a promising technology to discriminate eyes with different severity of DR.

Translational Relevance

Our study investigated OCTA metrics and severity of DR. At different stages of DR, ophthalmologists may focus on specific OCTA parameters to predict the progression of retinopathy in individual patients.

Optical Coherence Tomography Angiography for the Evaluation of Retinal Vasculature in Fabry Disease: Our Experience and Review of Current Knowledge

Purpose: Optical coherence tomography angiography (OCTA) is a non-invasive and objective tool for the evaluation of the retinal microvascular changes in Fabry disease (FD). We investigated changes in retinal vasculature in FD patients, and the possible correlation with systemic parameters, by using OCTA, and reviewed the current status of literature.

Methods: Thirteen FD patients (eight females, five males, mean age 49.85 ± 14.7 years) were compared with 13 age- and sex-matched healthy controls. OCTA 3 × 3 mm macular scans were performed in all subjects. We evaluated the vessel density and vessel perfusion in distinct macular areas (whole, inner, and outer) of both the superficial capillary plexus (SCP VD and SCP VP) and of the deep capillary plexus (DCP VD and DCP VP). We also evaluated the foveal avascular zone (FAZ) metrics (area, perimeter, and circularity), and correlation between systemic and OCTA parameters. A literature review on the current understanding of OCTA in FD is then presented.

Results: FD patients showed significantly lower SCP VD values in the whole area (17.37 ± 2.08 mm⁻¹ vs. 18.54 ± 1.21 mm⁻¹; p-value 0.022), as well as in the outer area (17.46 ± 2.10 mm⁻¹ vs. 19.08 ± 1.14 mm⁻¹; p-value 0.002), but not in the inner. Even the DCP VD was significantly lower in all the imaged areas: whole (17.75 ± 3.93 mm⁻¹ vs. 19.71 ± 1.20 mm⁻¹; p-value 0.024), outer (18.25 ± 4.17 mm⁻¹ vs. 20.33 ± 1.20 mm⁻¹; p-value 0.023), and inner (19.54 ± 4.17 mm⁻¹ vs. 21.96 ± 1.55 mm⁻¹; p-value 0.011). There were no significant differences in vessel perfusion parameters (both SCP VP and DCP VP ones) and FAZ. No significant correlations were found between the OCTA parameters and systemic parameters (maximal left ventricular wall thickness and glomerular filtration rate) in FD patients.

Conclusions: OCTA can be considered as a promising non-invasive tool, which enables a quantitative evaluation of retinal vascular involvement in FD, despite the varying data reported in literature. Our results support the use of OCTA as an objective tool to evaluate retinal vascular abnormalities in FD. The utility of OCTA in FD needs to be validated by longitudinal studies taking into account the overall progression of the disease.

Globotrioasylsphingosine Levels and Optical Coherence Tomography Angiography in Fabry Disease Patients

Background: To date, there are no studies associating the dried blood spot (DBS) levels of globotrioasylsphingosine (lysoGb3) with quantitative optical coherence tomography angiography (OCTA) parameters in Fabry disease (FD) patients. Here, we aimed to investigate the association between OCTA vessel density (VD), vessel length density (VLD) with DBS lysoGb3. Methods: A retrospective, single center analysis of all consecutive FD patients enrolled at the Department of Ophthalmology of the University Hospital of Zurich from 1 December 2017 to 9 September 2020. An association between VD and VLD detected by OCTA and lysoGb3 was investigated using a linear mixed model. Results: A total of 57 FD patients (23 male, 34 female; 109 eyes) were included. Forty-one patients suffered from the classic phenotype and 16 from the later-onset phenotype. LysoGb3 inversely correlated with VD and VLD in both the superficial (VD: p = 0.034; VLD: p = 0.02) and deep capillary plexus (VD: p = 0.017; VLD: p = 0.018) in the overall FD cohort. Conclusions: Our study shows an association between lysoGb3 and OCTA VD and VLD. This supports the hypothesis that quantitative OCTA parameters might be useful as diagnostic biomarkers for evaluating systemic involvement in FD, and possibly other diseases.

The Contribution of Ocular Biomarkers in the Differential Diagnosis of Alzheimer's Disease versus Other Types of Dementia and Future Prospects

With dementia becoming increasingly prevalent, there is a pressing need to become better equipped with accurate diagnostic tools that will favorably influence its course via prompt and specific intervention. The overlap in clinical manifestation, imaging, and even pathological findings between different dementia syndromes is one of the most prominent challenges today even for expert physicians. Since cerebral microvasculature and the retina share common characteristics, the idea of identifying potential ocular biomarkers to facilitate diagnosis is not a novel one. Initial efforts included studying less quantifiable parameters such as aspects of visual function, extraocular movements, and funduscopic findings. However, the really exciting prospect of a non-invasive, safe, fast, reproducible, and quantifiable method of pinpointing novel biomarkers has emerged with the advent of optical coherence tomography (OCT) and, more recently, OCT angiography (OCTA). The possibility of analyzing multiple parameters of retinal as well as retinal microvasculature variables in vivo represents a promising opportunity to investigate whether specific findings can be linked to certain subtypes of dementia and aid in their earlier diagnosis. The existing literature on the contribution of the eye in characterizing dementia, with a special interest in OCT and OCTA parameters will be reviewed and compared, and we will explicitly focus our effort in advancing our understanding and knowledge of relevant biomarkers to facilitate future research in the differential diagnosis between Alzheimer's disease and common forms of cognitive impairment, including vascular dementia, frontotemporal dementia, and dementia with Lewy bodies.

Quantitative evaluation of retinal and choroidal changes in Fabry disease using optical coherence tomography angiography

To examine the retinal and choroidal changes in patients with Fabry disease (FD) using optical coherence tomography angiography (OCTA). FD patients and age- and sex-matched healthy subjects were enrolled. A detailed ophthalmological examination was performed for all participants. The retinal thickness, ganglion cell layer with inner plexiform layer (GCIPL) thickness, choroidal thickness (CT), vessel length density (VLD), vessel perfusion density (VPD), and foveal avascular zone (FAZ) were analyzed in a detailed way with OCTA. Moreover, all FD patients underwent several laboratory tests to evaluate systemic conditions. A total of 54 subjects comprising 26 FD patients and 28 normal controls were enrolled. The retinal thickness, GCIPL thickness, and FAZ area showed no significant differences between the two groups (all P > 0.05). Only the superior CT in FD patients was significantly thinner than that in the normal subjects (P = 0.040). The macular VLD and VPD in the FD group were significantly reduced compared with the healthy controls (P = 0.026, P = 0.008). The macular VLD in FD patients had no significant correlations with different laboratory results (all P > 0.05), while the macular VPD were negatively correlated with creatinine (r = - 0.432, P = 0.028) and cystatin C (r = - 0.422, P = 0.032). FD patients may have retinal vascular dropout and choroidal vascular alterations. Analysis of vessel density using OCTA might be useful in the clinical assessment in FD patients.

The Retinal Vessel Density as a New Vascular Biomarker in Multisystem Involvement in Fabry Disease: An Optical Coherence Tomography Angiography Study

In this study, we evaluated the possible relationship between the changes in retinal vessel density (VD) by optical coherence tomography angiography (OCTA) and the vascular alterations involving renal, cardiovascular and central nervous systems in patients affected by Fabry disease (FD). In 50 FD patients, the retinal superficial capillary plexus (SCP) and deep capillary plexus (DCP) in macular region were evaluated by OCTA examination. The patients also underwent a brain magnetic resonance imaging scan, renal and echocardiographic examinations with quantification of systolic pulmonary arterial pressure (PAPs) and left atrial volume index (LAVi). The VD of SCP and DCP was inversely related with E/e’ ratio, LAVi, interventricular septal thickness, global longitudinal strain (GLS) and PAPs (p < 0.05). No relationship was found, with a multivariate analysis, between OCTA parameters and kidney function and neuroradiological signs of central nervous system involvement. OCTA could be a new vascular biomarker in FD, revealing a strong correlation between retinal capillary damage and myocardial impairment, possibly preceding both renal dysfunction and cerebrovascular involvement.

Evaluation of the reasons for the microvascular changes in patients with Fabry disease using optic coherence tomography angiography

PURPOSE

To investigate the blood flow changes in the choriocapillaris and the superficial and deep capillary plexus of the retina using optic coherence tomography angiography (OCTA) in patients with Fabry disease (FD) and reveal any possible association of these changes with the systemic findings.

METHODS

This cross-sectional study included 38 patients with FD and age- and gender-matched 40 healthy controls. OCTA images were obtained from all patients. Superficial (sCVD) and deep capillary vascular density (dCVD) in the foveal, parafoveal, and perifoveal zones and the whole image were recorded for each patient. Flow area in the choriocapillaris and central macular thickness (CMT) were also recorded.

RESULTS

Patients with FD showed a lower whole image (54.45 ± 5.99% vs 57.32 ± 6.71%, p = 0.004), foveal (34.94 ± 7.60% vs 39.65 ± 7.03%, p = 0.003), parafoveal (57.41 ± 4.85% vs 59.19 ± 4.67%, p = 0.043), and perifoveal (55.87 ± 6.43% vs 58.87 ± 7.02%, p = 0.003) dCVD compared to the healthy controls without a significant difference in the sCVD and choriocapillaris blood flow (p > 0.05). A significantly lower whole image and foveal dCVD in the FD patients with renal involvement was observed compared to the healthy controls (p = 0.027 and p = 0.024, respectively) without any significant difference between the FD patients without renal involvement and healthy controls (p = 0.17 and p = 0.13, respectively). CMT was significantly higher in FD patients with renal involvement compared to the ones without renal involvement (252.1 ± 18.5 µm vs 235.5 ± 17.6 µm, p = 0.016).

CONCLUSION

Patients with FD showed a lower dCVD without any change in sCVD and choriocapillaris compared to the healthy controls. This decrease was associated mostly with the renal involvement and duration of treatment.

Optical coherence tomography angiography analysis of fabry disease

PURPOSE

Fabry disease (FD) is characterized by a deficiency in α-galactosidase A activity that leads to the cumulative deposition of unmetabolized glycosphingolipids within organs, including the vascular endothelium and the eyes. The purpose of this study was to assess the effects of FD on the retinal microvasculature, foveal avascular zone (FAZ), macular thickness and retinal nerve fiber layer (RNFL) using optical coherence tomography angiography (OCT-A).

METHODS

Twenty-five patients (14 female and 11 male; mean age 33.16 ± 11.44) with genetically verified FD were compared with 37 age- and sex-matched healthy controls (mean age 32.36 ± 15.54). The vessel density (VD) values of the superficial and deep capillary plexuses (SCP and DCP), the area of the FAZ, the density of radial peripapillary capillaries (RPC), the macular thickness and the retinal nerve fiber layer thickness were measured by OCT-A examination.

RESULTS

The patients showed significantly lower VD values than controls in the foveal regions of both SCP and the DCP (21.15 ± 5.56 vs. 23.79 ± 4.64 (p = 0.048), 37.92 ± 6.78 vs. 41.11 ± 5.59 (p = 0.048), respectively). The FAZ was significantly larger in the FD group than in the control group (0.3 ± 0.1 vs. 0.24 ± 0.08 (p = 0.011)). No significant difference was identified in measurements of RPC density, peripapillary RNFL thickness or macular thickness between the two groups (p > 0.05 for all).

CONCLUSION

Decreased VD and an enlarged foveal avascular area suggest possible changes in the retinal microvasculature of patients with FD. OCT-A can serve as a useful, noninvasive, quantitative tool for diagnosing FD and monitoring its progression.

Computer-assisted retinal vessel diameter evaluation in Fabry disease

PURPOSE

Fabry disease retinal vascular involvement has been widely reported, with narrowing of the retinal arterioles, dilation and irregularity of the retinal veins, and exaggerated tortuosity of the retinal vessels. We evaluated retinal vessel diameter in Fabry disease, by means of a dedicated software, aiming to provide a quantitative marker of retinal vascular network abnormalities in Fabry disease patients.

MATERIAL AND METHODS

Observational case-control study evaluating different branches of vessels, peripapillary vessels (group A), temporal vascular arcades (group B), and second-order collaterals of the temporal arcades (group C). We obtained the vessel diameters values from eye fundus digital images of eight Fabry disease patients and eight age-sex matched controls, using a semiautomatic software. Mann-Whitney test was used to compare the Fabry disease group versus the control group.

RESULTS

The difference between the average diameters of all the types of vessels considered were significantly smaller in Fabry disease patients compared to healthy controls, resulting in a decrease in size (mm) of 10.9% for group A, 7.8% for group B, and 7.4% for group C. The most evident difference between Fabry disease patients and controls was found in the largest vessels.

CONCLUSION

A computer-assisted analysis of retinal vessel diameter in Fabry disease by means of dedicated software showed narrower retinal arteries in Fabry disease patients than in controls. Our data support the use of semiautomatic assessment of retinal vessel attenuation as an objective and reproducible method to evaluate retinal vascular alterations in Fabry disease, providing a clinical non-invasive tool for early diagnosis and disease monitoring.