Longitudinal characterization of retinal vasculature alterations with optical coherence tomography angiography in a mouse model of tauopathy

Tauopathies are a family of neurodegenerative diseases which predominately afflict the rapidly growing aging population suffering from various brain disorders including Alzheimer's disease, frontotemporal dementia with parkinsonism-17 and Pick disease. As the only visually accessible region of the central nervous system, in recent years, the retina has attracted extensive attention for its potential as a target for visualizing and quantifying emerging biomarkers of neurodegenerative diseases. Our previous study has found that retinal vascular inflammation and leakage occur at the very early stage of tauopathic mouse model. Here, we aimed to non-invasively visualize age-dependent alterations of retinal vasculature assessing the potential for using changes in retinal vasculature as the biomarker for the early diagnosis of tauopathy. Optical coherence tomography angiography (OCTA), a non-invasive depth-resolved high-resolution imaging technique was used to visualize and quantify tauopathy-induced alterations of retinal vasculature in P301S transgenic mice overexpressing the P301S mutant form of human tau and age-matched wild type littermate mice at 3, 6 and 10 months of age. We observed significant alterations of vascular features in the intermediate capillary plexus (ICP) and deep capillary plexus (DCP) but not in the superficial vascular complex (SVC) of P301S mice at early stages of tauopathy. With aging, alterations of vascular features in P301S mice became more prominent in all three vascular plexuses. Staining of retinal vasculature in flatmounts and trypsin digests of P301S mice at 10 months of age revealed decreased vessel density and increased acellular capillary formation, indicating that vascular degeneration also occurs during tauopathy. Overall, our results demonstrate that the changes in retinal vascular features accelerate during the progression of tauopathy. Vessels in the ICP and DCP may be more susceptible to tauopathy than vessels in the SVC. Since changes in retinal vasculature often precede tau pathology in the brain, non-invasive identification of retinal vascular alterations with OCTA may be a useful biomarker for the early diagnosis of tauopathy and monitoring its progression.

Optical coherence tomography of retinal and choroidal layers in patients with familial hypercholesterolaemia treated with lipoprotein apheresis

PURPOSE

Detect and quantify morpho-functional alterations of the retina and choroid in patients affected by familial hypercholesterolemia (FH) treated with lipoprotein apheresis (LA) using optic coherence tomography (OCT) and optic coherence tomography-angriography (OCTA).

DESIGN

Observational study.

SUBJECTS

To be diagnosed: A group of 20 patients (40 eyes) being clinically and genetically diagnosed as FH and under treatment (FH-Group)", for at least 2 years, was compared to a control group of 20 healthy subjects (40 eyes), with a normal lipid profile and no ocular disease (CT-Group).

METHODS

Participants were studied with the slit lamp, binocular indirect fundoscopy, OCT and OCTA.

MAIN OUTCOME MEASURES

Best corrected visual acuity (BVCA), spherical equivalent (SE), intraocular pressure (IOP), central macular thickness (CMT), choroidal thickness (CHT), retinal nerve fiber layer in four quadrants (RNFL (Superior = Sup; Inferior = Inf; Nasal = Nas Temporal = Temp), and the mean value across the four quadrants (RNFL G), foveal avascular zone (FAZ) and vascular density (VD).

RESULTS

FH subjects had smaller RNFL superiorly (108 ± 19,38 μm OD/111 ± 16,56 μm OS FH-Group vs 127 ± 7,42 μm OD/129 ± 14,64 μm OS CT-Group; P < 0,001 for both OD and OS) and inferiorly (108 ± 23,58 μm OD/115 ± 17,33 μm OS FH-Group vs 128 ± 18,15 μm OD/133 ± 17,38 μm OS CT-Group; P = 0,002 OD; P = 0,001 OS). G RNFL was consequently smaller (93 ± 12,94 μm OD/94 ± 10,49 μm OS FH-Group vs 101 ± 9,01 μm OD/101 ± 10,20 μm OS CT-Group; P = 0,03 OD; P = 0,02 OS). FH subjects had a larger FAZ (0,31 ± 0,08 mm² OD/0,33 ± 0,10 mm² in OS FH-Group vs 0,21 ± 0,05 mm² OD/0,21 ± 0,07 mm² OS CT-Group; P < 0,001 OD; P = 0,002 OS).

CONCLUSIONS

Early signs of retinal vessel damage in FH patients can be detected and quantified with OCT and OCTA.