Subclinical optic neuropathy in Fabry disease

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.

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.

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.

Corneal endothelial cell density and microvascular changes of retina and optic disc in autosomal dominant polycystic kidney disease

Purpose:

Vascular endothelial dysfunction in autosomal dominant polycystic kidney disease (ADPKD) may affect the retinal vascular parameters due to structural similarities of kidney and retina. We aimed to evaluate the microvascular changes of retina and optic disc and also corneal endothelial cell density in patients with ADPKD.

Methods:

Forty-six eyes of 23 patients with ADPKD (Group 1), and 46 eyes of 23 sex- and age-matched healthy controls (Group 2) were included in this cross-sectional study. Demographic and ophthalmic findings of participants were collected. Corneal endothelial cell density (CECD) measurements were obtained by noncontact specular microscopy. Foveal retinal thickness, peripapillary retinal nerve fiber layer (RNFL) thickness, vessel density in different sections of the retina and optic nerve head were analyzed by optical coherence tomography angiography.

Results:

The mean ages were 41 ± 11 years for Group 1 and 39 ± 10 years for Group 2 (P = 0.313). CECD values were significantly lower in group 1 when compared to group 2 (2653 ± 306 cells/mm² and 2864 ± 244 cells/mm², respectively, P < 0.001). The foveal retinal thickness and RNFL thickness were similar, but superior quadrant thickness of RNFL was significantly lower in Group 1 than Group 2 (126 ± 14 μm vs. 135 ± 15 μm, P = 0.003). In Group 1, whole image of optic disc radial peripapillary capillary densities were significantly lower compared to Group 2 (49.4 ± 2.04%, and 50.0 ± 2.2%, respectively, P = 0.043). There was no significant difference regarding superficial, deep retinal vessel densities, foveal avascular zone and flow areas between the groups (P > 0.05 for all).

Conclusion:

Lower CECD values and decreased superior quadrant RNFL thickness, and microvascular densities of optic disc were revealed in patients with ADPKD. Evaluation of CECD and retinal microvasculature may be helpful in the management of these 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.

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.

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

Purpose

Fabry disease (FD) is a multiorgan X-linked condition characterized by a deficiency of the lysosomal enzyme alpha-galactosidase A, resulting in a progressive intralysosomal deposit of globotriaosylceramide. The aim of this study was to evaluate the macular ultrastructure of the vascular network using optical coherence tomography angiography (OCTA) and to evaluate macular function using focal electroretinography (fERG) in Fabry patients (FPs).

Methods

A total of 20 FPs (38 eyes, mean age 57 ± 2.12 SD, range of 27-80 years) and 17 healthy controls (27 eyes, mean age 45 years ± 20.50 SD, range of 24-65 years) were enrolled in the study. Color fundus photography, swept-source optical coherence tomography (SS-OCT), OCTA and fERG were performed in all subjects. The OCTA foveal avascular zone (FAZ), vasculature structure, superficial and deep retinal plexus densities (images of 4.5 × 4.5 mm) and fERG amplitudes were measured. Group differences were statistically assessed by Student's t-test and ANOVA.

Results

In the FP group, the FAZ areas of the superficial and deep plexuses were enlarged (P = 0.036, t = 2.138; P < 0.001, t = -3.889, respectively), the vessel density was increased in the superficial plexus, and the fERG amplitude was reduced (P < 0.001, t = -10.647) compared with those in healthy controls. No significant correlations were found between the structural and functional data.

Conclusions

OCTA vascular abnormalities and reduced fERG amplitudes indicate subclinical signs of microangiopathy with early retinal dysfunction in FPs. This study highlights the relevance of OCTA imaging analysis in the identification of abnormal macular vasculature as an ocular hallmark of FD.

Longitudinal study on ocular manifestations in a cohort of patients with Fabry disease

Purpose

This study aims to assess the evolution of ocular manifestations in a cohort of Fabry patients.

Methods

This is a prospective observational study conducted from 2013 to 2017 (5 consecutive exams). All subjects underwent a comprehensive ocular examination including oriented case history, refraction, corneal topography, biomechanical corneal properties and pachometry assessments, aberrometry, anterior segment evaluation, double-frequency visual field (FDT), intra-ocular pressure, and ocular fundus. At baseline, 41 subjects enrolled but 9 dropped-out and 4 files were not kept for analysis (missing data). Remaining 28 subjects were classified into: Group 1 -hemizygotes (HMZ), all on enzyme replacement therapy (ERT) (N = 10); Group 2 -heterozygotes (HTZ) actively ERT-treated (N = 8), and Group 3 -HTZ not treated (N = 10).

Results

There is a high intra and inter-subjects variability. At baseline, prevalence of the ocular manifestations found is similar to published data: cornea verticillata (89.2%), conjunctival vessels tortuosity (85.7%), corneal haze (67.8%), retinal vessels tortuosity (64.2%), anterior cataract (39.2%) and posterior cataract (28.5%). Prevalence for new elements are found: upper lid vessels toricity (96.4%) and micro-aneurysms (42.8%). At the end, micro-aneurysms (+82%), posterior cataract (+75%) corneal haze (+21%) anterior cataract (+17%) and retinal vessels tortuosities (+4%) evolved in prevalence and severity despite the fact that 68% of the patients were on ERT. Treated heterozygotes evolved more than other groups (p>0.05).

Conclusion

ERT does not seem to halt the clinical evolution of several ocular manifestations. Longer observational time and objective grading systems may be required to fully confirm these findings.

[The neurological manifestations of Fabry disease. A review]

Fabry disease (Anderson-Fabry disease) is an X-linked recessive lysosomal storage disorder resulting from deficient activity of lysosomal hydrolase, alpha-galactosidase A (alpha-Gal A), which leads to progressive accumulation of globotriaosylceramide (Gb3) in various cells, predominantly endothelial and vascular smooth muscle cells, with clinical manifestations affecting major organs including the central nervous system. Manifestations of Fabry disease include progressive renal and cardiac insufficiency, neuropathic pain, stroke and cerebral disease, skin and gastrointestinal symptoms. Clinical onset usually occurs in childhood, but many severe patients are diagnosed in adulthood. Females may be severely affected as males and both may die prematurely due to stroke, heart disease and renal failure. Early recognition of symptoms, enzyme activity levels, concentration of Gb3 levels in the blood, urine and skin biopsies, as well as genetic testing (GLA gene) enable establishment of early diagnosis and therapeutic intervention with enzyme replacement therapy. Enzyme replacement therapy can stabilize or reduce the progression of the disease. Early therapy may prevent complications of the disease.