Vision Loss in Optic Disc Drusen Correlates With Increased Macular Vessel Diameter and Flux and Reduced Peripapillary Vascular Density

Dimension-based quantification of aging-associated cerebral microvasculature determined by optical coherence tomography and two-photon microscopy

Cerebral microvascular health is a key biomarker for the study of natural aging and associated neurological diseases. Our aim is to quantify aging-associated change of microvasculature at diverse dimensions in mice brain. We used optical coherence tomography (OCT) and two-photon microscopy (TPM) to obtain nonaged and aged C57BL/6J mice cerebral microvascular images in vivo. Our results indicated that artery & vein, arteriole & venule, and capillary from nonaged and aged mice showed significant differences in density, diameter, complexity, perimeter, and tortuosity. OCT angiography and TPM provided the comprehensive quantification for arteriole and venule via compensating the limitation of each modality alone. We further demonstrated that arteriole and venule at specific dimensions exhibited negative correlations in most quantification analyses between nonaged and aged mice, which indicated that TPM and OCT were able to offer complementary vascular information to study the change of cerebral blood vessels in aging.

An open-source deep learning network AVA-Net for arterial-venous area segmentation in optical coherence tomography angiography

BACKGROUND

Differential artery-vein (AV) analysis in optical coherence tomography angiography (OCTA) holds promise for the early detection of eye diseases. However, currently available methods for AV analysis are limited for binary processing of retinal vasculature in OCTA, without quantitative information of vascular perfusion intensity. This study is to develop and validate a method for quantitative AV analysis of vascular perfusion intensity.

METHOD

A deep learning network AVA-Net has been developed for automated AV area (AVA) segmentation in OCTA. Seven new OCTA features, including arterial area (AA), venous area (VA), AVA ratio (AVAR), total perfusion intensity density (T-PID), arterial PID (A-PID), venous PID (V-PID), and arterial-venous PID ratio (AV-PIDR), were extracted and tested for early detection of diabetic retinopathy (DR). Each of these seven features was evaluated for quantitative evaluation of OCTA images from healthy controls, diabetic patients without DR (NoDR), and mild DR.

RESULTS

It was observed that the area features, i.e., AA, VA and AVAR, can reveal significant differences between the control and mild DR. Vascular perfusion parameters, including T-PID and A-PID, can differentiate mild DR from control group. AV-PIDR can disclose significant differences among all three groups, i.e., control, NoDR, and mild DR. According to Bonferroni correction, the combination of A-PID and AV-PIDR can reveal significant differences in all three groups.

CONCLUSIONS

AVA-Net, which is available on GitHub for open access, enables quantitative AV analysis of AV area and vascular perfusion intensity. Comparative analysis revealed AV-PIDR as the most sensitive feature for OCTA detection of early DR. Ensemble AV feature analysis, e.g., the combination of A-PID and AV-PIDR, can further improve the performance for early DR assessment.

Early Retinal Microvasculopathy in Prediabetic Patients and Correlated Factors

INTRODUCTION

We aimed to detect early retinal microcirculation changes in prediabetic patients and investigate their correlation with clinical examinations.

METHODS

Forty-seven prediabetic individuals, 29 controls, and 81 type 2 diabetic mellitus (T2DM) patients were enrolled in this study. A review of clinical data and spectral-domain optical coherence tomography angiography (SD-OCTA) parameters of macular vessel diameter (VD), foveal avascular zone (FAZ), and macular vessel area density (VAD) was performed.

RESULTS

Levels of low-density lipoprotein cholesterol and triglycerides in prediabetes and T2DM groups were significantly higher than those in the control group. The urine microalbumin-to-creatinine ratio (ACR) was mildly and moderately increased in the prediabetes and T2DM groups, respectively. The estimated glomerular filtration rate of the three groups was within the normal range. SD-OCTA showed that VAD in the superficial macular area was decreased in the prediabetes group compared to the control group (p = 0.01). The FAZ size, particularly in the deep layer, was expanded in the prediabetes group. In the deep retinal layer of the macular area, VD and FAZ size in the prediabetes group were larger than those in the control group. In the prediabetes group, the axial length was significantly correlated with macular VD and FAZ size (p < 0.05), and ACR was correlated with FAZ size (p < 0.05). Age had a negative correlation with VAD (p < 0.01). ACR had a positive correlation with FAZ size (p < 0.05).

CONCLUSIONS

Enlargement and irregularity of the FAZ area, deep capillary dilation, and a decrease in VAD occur in the retina of prediabetic patients with mild kidney function impairment.

Comparison of Spectral-Domain OCT versus Swept-Source OCT for the Detection of Deep Optic Disc Drusen

Deep optic disc drusen (ODD) are located below Bruch’s membrane opening (BMO) and may go undetected due to the challenges in imaging them. The purpose of this study is a head-to-head comparison of currently widely used imaging technologies: swept-source optical coherence tomography (SS-OCT; DRI OCT-1 Triton, Topcon) and enhanced depth imaging spectral-domain optical coherence tomography (EDI SD-OCT; Spectralis OCT, Heidelberg Engineering) for the detection of deep ODD and associated imaging features. The eyes included in this study had undergone high-resolution imaging via both EDI SD-OCT and SS-OCT volume scans, which showed at least one deep ODD or a hyperreflective line (HL). Grading was performed by three graders in a masked fashion. The study findings are based on 46 B-scan stacks of 23 eyes including a total of 7981 scans. For scan images with ODD located above or below the level of BMO, no significant difference was found between the two modalities compared in this study. However, for HLs and other features, EDI SD-OCT scan images had better visualization and less artifacts. Although SS-OCT offers deep tissue visualization, it did not appear to offer any advantage in ODD detection over a dense volume scan via EDI SD-OCT with B-scan averaging.

Correlation Between Laser Speckle Flowgraphy and OCT-Derived Retinal and Choroidal Metrics in Healthy Human Eye

Purpose

To investigate the correlation between laser speckle flowgraphy (LSFG) signals and the quantitative metrics derived from optical coherence tomography (OCT) in normal eyes.

Methods

LSFG, OCT, and OCT angiography (OCTA) imaging were performed on normal participants using a custom-designed LSFG system and a commercial swept-source OCT system. Mean (PWM) and amplitude (PWA) of the LSFG pulse waveform were selected to quantify the LSFG signals. Retinal and choroidal maps were obtained using the standard 6 × 6 mm OCT and OCTA scans. Structural and vascular metrics maps, including thickness, vessel area density, vessel skeleton density, and vessel diameter index of the retina, and choroidal thickness (CT), choroidal vessel volume (CVV) and choroidal vessel index (CVI), were employed to quantify the retinal and choroidal properties. Correlation analysis was then performed between the LSFG, retinal, and choroidal metrics maps.

Results

Twelve healthy participants aged 23 to 36 years were enrolled in this study. The spatial distribution of the PWM and PWA values was highly correlated with that of the CT and CVV metrics. On average, Spearman correlation coefficients (ρ) were 0.80 and 0.78 (all P < 0.001) for the correlations between PWM and CT and CVV, respectively, and were 0.61 and 0.63 (all P < 0.05) for the correlations between PWA and CT and CVV, respectively. In comparison, both PWM and PWA were generally weak or not correlated with all the retinal metrics and CVI.

Conclusions

LSFG signals were positively correlated with the choroidal thickness and vessel volume, suggesting choroidal blood flows dominate the LSFG signals at the area absent of large retinal vessels.

Translational Relevance

This study illustrates the dominant source of the LSFG signals in the eye.

Updates on ophthalmic imaging features of optic disc drusen, papilledema, and optic disc edema

Purpose of review

Optic nerve head elevation can be associated with vision loss. This review provides an update regarding key features of optic disc drusen (ODD) compared with papilledema from increased intracranial pressure and optic disc edema from other causes.

Recent findings

Clinical history and funduscopic examination are not sufficient to correctly diagnose different causes of optic nerve head elevation. Multimodal ophthalmic imaging is noninvasive and should be used as first-line diagnostic testing to distinguish optic disc edema or papilledema from pseudoedema. Advanced ophthalmic imaging, including enhanced depth imaging optical coherence tomography (EDI-OCT) and autofluorescence imaging, can visualize ODD at high resolution and determine whether there is optic disc edema. OCT angiography does not require contrast and can rapidly visualize papillary, peripapillary, and macular microvasculature and identify important vascular biomarker of ischemia and, potentially, visual prognosis.

Summary

Multimodal ophthalmic imaging can help in the diagnosis of ODD and optic disc edema and identify patients at high risk of vision loss and neurological issues in order to ensure appropriate diagnosis and treatment.

Phenotypic Features and Genetic Findings in a Cohort of Italian Pseudoxanthoma Elasticum Patients and Update of the Ophthalmologic Evaluation Score

BACKGROUND

Pseudoxanthoma elasticum (PXE) is a rare ectopic calcification genetic disease mainly caused by ABCC6 rare sequence variants. The clinical phenotype is characterized by typical dermatological, ophthalmological and cardiovascular manifestations, whose frequency and severity are differently reported in the literature.

METHODS

A retrospective study was performed on 377 PXE patients of Italian origin, clinically evaluated according to the Phenodex Index, who underwent ABCC6 biomolecular analyses. Moreover, 53 PXE patients were further characterized by in-depth ophthalmological examinations.

RESULTS

A total of 117 different ABCC6 rare sequence variants were detected as being spread through the whole gene. The severity of the clinical phenotype was dependent on age, but it was not influenced by gender or by the type of sequence variants. In-depth ophthalmological examinations focused on the incidences of coquille d'oeuf, comet lesions, pattern dystrophy-like lesions, optic disk drusen and posterior-pole atrophy. Conclusion: Given the large number of patients analyzed, we were able to better evaluate the occurrence of less frequent alterations (e.g., stroke, myocardial infarction, nephrolithiasis). A more detailed description of ophthalmological abnormalities allowed us to stratify patients and better evaluate disease progression, thus suggesting a further update of the PXE score system.

Topographic Quadrant Analysis of Peripapillary Superficial Microvasculature in Optic Disc Drusen

Background: Limited information is known about the topographic effect of optic disc drusen (ODD) on peripapillary retinal nerve fibers and microvasculature. Objective: This study aims to understand the structural and functional impact of ODD in different quadrants of the optic disc. Methods: We performed a retrospective case-control study of 22 ODD patients (34 eyes) and 26 controls (33 eyes) to compare optical coherence tomography (OCT) retinal nerve fiber layer (RNFL), OCT angiography (OCTA), and corresponding static perimetry mean deviation (MD) calculated using the modified Garway-Heath map in different quadrants of the optic disc. OCTA was analyzed using custom MATLAB script to measure six parameters in a peripapillary annulus with large vessel removal: vessel area density (VAD), vessel skeleton density (VSD), vessel perimeter index (VPI), vessel complexity index (VCI), flux, and vessel diameter index (VDI). Results: Quadrant analysis revealed that OCTA VAD and VCI were significantly decreased in superior, nasal, and inferior but not temporal quadrant. RNFL, VSD, and VPI were significantly impacted only in the superior and nasal quadrants. Corresponding visual field MDs in all ODD eyes were not different in the four quadrants, although eyes with MD equal or worse than -5 dB (32%) had worst visual field corresponding to the superior quadrant of the optic disc (inferior arcuate visual field). Structure-structure comparison of OCT and OCTA showed high correlation of RNFL with multiple OCTA measurements in the superior, nasal, and inferior quadrants but not temporal quadrant. Structure-function analysis revealed significant correlation of VAD and VCI and visual field MD in every quadrant, but RNFL was only significantly correlated in the superior and inferior quadrants. Conclusions: Peripapillary VAD and VCI are decreased in more quadrants than RNFL, supporting the clinical utility of performing OCTA in addition to OCT. Consistent with the most common locations of ODD, five OCT/OCTA measurements (VAD, VCI, RNFL, VSD, VPI) are decreased in the superior and nasal quadrants. OCT/OCTA measurements were significantly impacted in contrast to the relatively mild effect on corresponding visual field MD, consistent with the idea that a decrease in objective structural and vascular measurements occurs without parallel change in subjective visual function in ODD.

Hypoxia-induced inflammation: Profiling the first 24-hour posthypoxic plasma and central nervous system changes

Central nervous system and visual dysfunction is an unfortunate consequence of systemic hypoxia in the setting of cardiopulmonary disease, including infection with SARS-CoV-2, high-altitude cerebral edema and retinopathy and other conditions. Hypoxia-induced inflammatory signaling may lead to retinal inflammation, gliosis and visual disturbances. We investigated the consequences of systemic hypoxia using serial retinal optical coherence tomography and by assessing the earliest changes within 24h after hypoxia by measuring a proteomics panel of 39 cytokines, chemokines and growth factors in the plasma and retina, as well as using retinal histology. We induced severe systemic hypoxia in adult C57BL/6 mice using a hypoxia chamber (10% O2) for 1 week and rapidly assessed measurements within 1h compared with 18h after hypoxia. Optical coherence tomography revealed retinal tissue edema at 18h after hypoxia. Hierarchical clustering of plasma and retinal immune molecules revealed obvious segregation of the 1h posthypoxia group away from that of controls. One hour after hypoxia, there were 10 significantly increased molecules in plasma and 4 in retina. Interleukin-1β and vascular endothelial growth factor were increased in both tissues. Concomitantly, there was significantly increased aquaporin-4, decreased Kir4.1, and increased gliosis in retinal histology. In summary, the immediate posthypoxic period is characterized by molecular changes consistent with systemic and retinal inflammation and retinal glial changes important in water transport, leading to tissue edema. This posthypoxic inflammation rapidly improves within 24h, consistent with the typically mild and transient visual disturbance in hypoxia, such as in high-altitude retinopathy. Given hypoxia increases risk of vision loss, more studies in at-risk patients, such as plasma immune profiling and in vivo retinal imaging, are needed in order to identify novel diagnostic or prognostic biomarkers of visual impairment in systemic hypoxia.

Kinetic and static perimetry after 16 years and additional OCT-A analysis in eyes with long-lasting optic disc drusen

The aim of the study is to evaluate the progression of visual field (VF) defects over 16 years of observation and to assess abnormalities in vessels and retinal nerve fibre layer (RNFL) thickness in patients with optic disc drusen (ODD). Both static automated perimetry (SAP) and semi-automated kinetic perimetry (SKP) were performed in 16 eyes of 8 patients (mean age 54 years) with ODD among 26 eyes of 13 patients examined 16 years before. The area of I2e, I4e, III4e, and V4e isopters was measured in deg2. The MD and PSD parameters were estimated using SAP. Optical coherence tomography angiography (OCT-A) was additionally performed in 16 ODD eyes and 16 eyes of 8 healthy subjects to estimate the RNFL thickness and vessel density of the optic nerve disc and the macula. The differences in all isopter areas of SKP and SAP parameters after 16 years were not significant. The analysis of OCT-A showed a significant reduction of the vessel density and RNFL of the peripapillary area in each segment in patients with ODD, compared with the control group. The highest reduction of RNFL was observed in the superior segment of the optic disc area (92.56μm vs 126.63μm) also the macular thickness was decreased in ODD patients, compared with the control group. In the macula, there was a significant vascular defect in the whole superficial layer and in the parafoveal deep layer. A strong significant correlation of the parafoveal deep plexus with MD and PSD parameters was detected. In conclusion, VF loss due to ODD after 16 years of the follow-up was not significant both in SKP and SAP. ODD caused a reduced vessel density and RNFL, as well as macular thickness in OCT-A. SAP parameters were influenced by parafoveal deep plexus.

Optical coherence tomography angiography in neuro-ophthalmology: Current clinical role and future perspectives

Optical coherence tomography angiography (OCTA) is a noninvasive, depth-resolved imaging tool for the appraisement of retinal vascular changes. Since its introduction, the understanding of diabetic retinopathy, age-related macular degeneration, central serous retinopathy, and other diseases has been enriched on many fronts. Its dyeless imaging property maps retinal as well as deeper choroidal vasculature in quick succession with good reproducibility. Hence, it can play an important role in the diagnosis and management of optic nerve-related diseases as well. A detailed literature review for its role in nonarteritic anterior ischemic optic neuropathy, papilledema, optic disc drusen, papillitis, hereditary optic neuropathies, central nervous system diseases, and others highlights its role. The whole spectrum of neuro-ophthalmological diseases shows consistent peripapillary and macular capillary changes with structural and functional correlation. The superficial and deeper retinal and choroidal vasculatures are affected depending on the nature of the disease process. Hence, OCTA positions itself as a useful, noninvasive tool in the armamentarium of a neuro-ophthalmologist in future; however, there are several limitations of the OCTA with respect to its technical abilities in challenging neuro-ophthalmic cases. Therefore, future research should be directed to enhance the technical capabilities of OCTA and to determine the more precise role of it in the prognosis of neuro-ophthalmic diseases.

Diagnosing Optic Disc Drusen in the Modern Imaging Era: A Practical Approach

Optic disc drusen (ODD) are a well-recognised cause of an elevated optic disc appearance. When visible with ophthalmoscopy and fundus photography, ODD are readily identified. Yet, in more subtle cases of ODD, ancillary testing may be needed to render the diagnosis. Facilitating the diagnosis of ODD has clinical relevance, because affected individuals may otherwise undergo unnecessary costly and invasive investigations to rule out raised intracranial pressure and other causes of optic disc oedema. In this review, the role of established and emerging optical coherence tomography (OCT) techniques in the diagnosis and management of ODD cases is reviewed. A practical approach is taken to explain how to optimise use of commercially available OCT technology in the clinical setting. Optical coherence tomography provides many advantages over other imaging modalities in the diagnosis of ODD, including the ability to correlate retinal measures of neuroaxonal structure with drusen characteristics. Earlier spectral domain OCT techniques, however, were hindered by poor penetrance. In the modern imaging era, enhanced depth imaging OCT and swept source OCT enable higher resolution of ODD and other optic nerve head structures that might otherwise be mistaken for drusen. Ongoing studies featuring OCT angiography indicate that this technique may provide complementary information about microvascular supply that correlate with structural measures of optic nerve injury. Advances in OCT will continue to improve diagnostic accuracy and inform clinical understanding regarding structure-function correlations germane to the longitudinal follow up of ODD patients.