Age-related changes of the retinal microvasculature

Convolutional Neural Network-Based Prediction of Axial Length Using Color Fundus Photography

Purpose

To develop convolutional neural network (CNN)-based models for predicting the axial length (AL) using color fundus photography (CFP) and explore associated clinical and structural characteristics.

Methods

This study enrolled 1105 fundus images from 467 participants with ALs ranging from 19.91 to 32.59 mm, obtained at National Taiwan University Hospital between 2020 and 2021. The AL measurements obtained from a scanning laser interferometer served as the gold standard. The accuracy of prediction was compared among CNN-based models with different inputs, including CFP, age, and/or sex. Heatmaps were interpreted by integrated gradients.

Results

Using age, sex, and CFP as input, the mean ± standard deviation absolute error (MAE) for AL prediction by the model was 0.771 ± 0.128 mm, outperforming models that used age and sex alone (1.263 ± 0.115 mm; P < 0.001) and CFP alone (0.831 ± 0.216 mm; P = 0.016) by 39.0% and 7.31%, respectively. The removal of relatively poor-quality CFPs resulted in a slight MAE reduction to 0.759 ± 0.120 mm without statistical significance (P = 0.24). The inclusion of age and CFP improved prediction accuracy by 5.59% (P = 0.043), while adding sex had no significant improvement (P = 0.41). The optic disc and temporal peripapillary area were highlighted as the focused areas on the heatmaps.

Conclusions

Deep learning-based prediction of AL using CFP was fairly accurate and enhanced by age inclusion. The optic disc and temporal peripapillary area may contain crucial structural information for AL prediction in CFP.

Translational Relevance

This study might aid AL assessments and the understanding of the morphologic characteristics of the fundus related to AL.

Retinal microvascular complexity as a putative biomarker of biological age: a pilot study

Physiological changes associated with aging increase the risk for the development of age-related diseases. This increase is non-specific to the type of age-related disease, although each disease develops through a unique pathophysiologic mechanism. People who age at a faster rate develop age-related diseases earlier in their life. They have an older "biological age" compared to their "chronological age". Early detection of individuals with accelerated aging would allow timely intervention to postpone the onset of age-related diseases. This would increase their life expectancy and their length of good quality life. The goal of this study was to investigate whether retinal microvascular complexity could be used as a biomarker of biological age. Retinal images of 68 participants ages ranging from 19 to 82 years were collected in an observational cross-sectional study. Twenty of the old participants had age-related diseases such as hypertension, type 2 diabetes, and/or Alzheimer's dementia. The rest of the participants were healthy. Retinal images were captured by a hand-held, non-mydriatic fundus camera and quantification of the microvascular complexity was performed by using Sholl's, box-counting fractal, and lacunarity analysis. In the healthy subjects, increasing chronological age was associated with lower retinal microvascular complexity measured by Sholl's analysis. Decreased box-counting fractal dimension was present in old patients, and this decrease was 2.1 times faster in participants who had age-related diseases (p = 0.047). Retinal microvascular complexity could be a promising new biomarker of biological age. The data from this study is the first of this kind collected in Montenegro. It is freely available for use.

Understanding human aging and the fundamental cell signaling link in age-related diseases: the middle-aging hypovascularity hypoxia hypothesis

Aging-related hypoxia, oxidative stress, and inflammation pathophysiology are closely associated with human age-related carcinogenesis and chronic diseases. However, the connection between hypoxia and hormonal cell signaling pathways is unclear, but such human age-related comorbid diseases do coincide with the middle-aging period of declining sex hormonal signaling. This scoping review evaluates the relevant interdisciplinary evidence to assess the systems biology of function, regulation, and homeostasis in order to discern and decipher the etiology of the connection between hypoxia and hormonal signaling in human age-related comorbid diseases. The hypothesis charts the accumulating evidence to support the development of a hypoxic milieu and oxidative stress-inflammation pathophysiology in middle-aged individuals, as well as the induction of amyloidosis, autophagy, and epithelial-to-mesenchymal transition in aging-related degeneration. Taken together, this new approach and strategy can provide the clarity of concepts and patterns to determine the causes of declining vascularity hemodynamics (blood flow) and physiological oxygenation perfusion (oxygen bioavailability) in relation to oxygen homeostasis and vascularity that cause hypoxia (hypovascularity hypoxia). The middle-aging hypovascularity hypoxia hypothesis could provide the mechanistic interface connecting the endocrine, nitric oxide, and oxygen homeostasis signaling that is closely linked to the progressive conditions of degenerative hypertrophy, atrophy, fibrosis, and neoplasm. An in-depth understanding of these intrinsic biological processes of the developing middle-aged hypoxia could provide potential new strategies for time-dependent therapies in maintaining healthspan for healthy lifestyle aging, medical cost savings, and health system sustainability.

Improvement of Retinal Capillary Function After High-Speed Circuit Resistance Training in Healthy Older Adults

BACKGROUND

To determine the retinal capillary function (RCF, the efficiency of blood flow transferring in the capillary network) and its relation to cognitive function in healthy older people without known cognitive impairment following an 8-week high-speed circuit resistance training program (HSCT).

METHODS

Eleven subjects in the HSCT group and 7 age-matched nontraining controls (CON) were recruited. The HSCT group trained 3 times per week for 8 weeks, whereas CON performed no formal training. One eye of each subject from both groups was imaged at baseline and 8-week follow-up. Retinal blood flow (RBF) was measured using a retinal function imager, and retinal capillary density (RCD, expressed as fractal dimension Dbox) was measured using optical coherence tomography angiography. RCF was defined as the ratio of RBF to RCD. Cognitive function was assessed during both visits using the NIH Toolbox Fluid Cognition Battery.

RESULTS

RCF was 2.07 ± 0.64 nL⋅s -1 ·Dbox -1 (mean ± SD) at baseline, and significantly increased to 2.59 ± 0.54 nL⋅s -1 ·Dbox -1 after training ( P = 0.0003) in the HSCT group, reflecting an increase of 25%. The changes of RBF were not related to the changes of RCD in the HSCT group (r = -0.18, P = 0.59). There was no significant change of RCF in the CON group ( P = 0.58). In the HSCT group, the Pattern Comparison Processing Speed Test and Fluid Cognition Composite Score were significantly increased after HSCT ( P = 0.01). Furthermore, the changes in Flanker Inhibitory Control and Attention Test (FLNK) were positively correlated to increases in RCF (r = 0.77, P = 0.005).

CONCLUSIONS

This is the first prospective study to demonstrate that the increased RCF after HSCT was related to improved cognition in cognitively normal older adults.

The Role of Oxidative Stress in the Aging Eye

Given the expanding elderly population in the United States and the world, it is important to understand the processes underlying both natural and pathological age-related changes in the eye. Both the anterior and posterior segment of the eye undergo changes in biological, chemical, and physical properties driven by oxidative stress. With advancing age, changes in the anterior segment include dermatochalasis, blepharoptosis, thickening of the sclera, loss of corneal endothelial cells, and stiffening of the lens. Changes in the posterior segment include lowered viscoelasticity of the vitreous body, photoreceptor cell loss, and drusen deposition at the macula and fovea. Age-related ocular pathologies including glaucoma, cataracts, and age-related macular degeneration are largely mediated by oxidative stress. The prevalence of these diseases is expected to increase in the coming years, highlighting the need to develop new therapies that address oxidative stress and slow the progression of age-related pathologies.

Assessment of factors affecting flicker ERGs recorded with RETeval from data obtained from health checkup screening

PURPOSE

To determine the factors significantly associated with the amplitudes and implicit times of the flicker electroretinograms (ERGs) recorded with the RETeval system by analyzing the comprehensive data obtained during a health checkup screening.

METHODS

Flicker ERGs were recorded with the RETeval system from 373 individuals who had a normal fundus and optical coherence tomography images. The sex, age, anthropometric, ophthalmologic, and hematologic data were collected from all participants who were 40- to 89-years-of-age. Univariable and multivariable linear mixed effects regression analyses were performed to identify factors that were significantly associated with the implicit times and amplitudes of the RETeval flicker ERGs.

RESULTS

Univariable linear mixed effects regression analysis showed significant correlations between the implicit times and the best-corrected visual acuity, the age, the axial length, the blood sugar level, and the blood urea nitrogen level. Analyses by multivariable linear mixed effects regression identified that the axial length (β = 0.28), the age (β = 0.24), and the blood sugar level (β = 0.092) were three independent factors that were significantly correlated with the implicit times of the RETeval flicker ERGs. Univariable linear mixed effects regression analysis also showed significant correlations between the amplitudes of the RETeval flicker ERGs and the age, the platelet count, and the creatinine level. Multivariable linear mixed effects regression models identified the age (β = -0.092), the platelet count (β = 0.099), and the creatinine level (β = -0.12) as three independent factors that were significantly correlated with the amplitudes of the RETeval flicker ERGs. However, the smoking habits, body mass index, and the blood pressure were not significantly correlated with either the implicit times or amplitudes of the RETeval flicker ERGs.

CONCLUSIONS

Our results indicate that the age and some ophthalmologic and hematologic findings but not the anthropometric findings were significantly associated with the implicit times and amplitudes of the RETeval flicker ERGs. Thus, clinicians should remember these factors when analyzing the RETeval flicker ERGs.

[Retinal vascular network: Changes with aging and systemic vascular disease (cardiac and cerebral)]

For over 10 years, the description of the retinal microvascular network has benefited from the development of new imaging techniques. Automated retinal image analysis software, as well as OCT angiography (OCT-A), are able to highlight subtle, early changes in the retinal vascular network thanks to a large amount of microvascular quantitative data. The challenge of current research is to demonstrate the association between these microvascular changes, the systemic vascular aging process, and cerebrovascular and cardiovascular disease. Indeed, a pathophysiological continuum exists between retinal microvascular changes and systemic vascular diseases. In the Montrachet study, we found that a suboptimal retinal vascular network, as identified by the Singapore I Vessel Assessment (SIVA) software, was significantly associated with treated diabetes and an increased risk of cardiovascular mortality. In addition, we supplemented our research on the retinal vascular network with the use of OCT-A. In the EYE-MI study, we showed the potential role of quantitative characterization of the retinal microvascular network by OCT-A in order to assess the cardiovascular risk profile of patients with a history of myocardial infarction. A high AHA (American Heart Association) risk score was associated with low retinal vascular density independently of hemodynamic changes. Thus, a better understanding of the association between the retinal microvasculature and macrovascular disease might make its use conceivable for early identification of at-risk patients and to suggest a personalized program of preventative care. The retinal vascular network could therefore represent an indicator of systemic vascular disease as well as an interesting predictive biomarker for vascular events.

An Analysis of Metabolic Changes in the Retina and Retinal Pigment Epithelium of Aging Mice

Purpose

The purpose of this study was to present our hypothesis that aging alters metabolic function in ocular tissues. We tested the hypothesis by measuring metabolism in aged murine tissues alongside retinal responses to light.

Methods

Scotopic and photopic electroretinogram (ERG) responses in young (3–6 months) and aged (23–26 months) C57Bl/6J mice were recorded. Metabolic flux in retina and eyecup explants was quantified using U-¹³C-glucose or U-¹³C-glutamine with gas chromatography-mass spectrometry (GC-MS), O₂ consumption rate (OCR) in a perifusion apparatus, and quantifying adenosine triphosphatase (ATP) with a bioluminescence assay.

Results

Scotopic and photopic ERG responses were reduced in aged mice. Glucose metabolism, glutamine metabolism, OCR, and ATP pools in retinal explants were mostly unaffected in aged mice. In eyecups, glutamine usage in the Krebs Cycle decreased while glucose metabolism, OCR, and ATP pools remained stable.

Conclusions

Our examination of metabolism showed negligible impact of age on retina and an impairment of glutamine anaplerosis in eyecups. The metabolic stability of these tissues ex vivo suggests age-related metabolic alterations may not be intrinsic. Future experiments should focus on determining whether external factors including nutrient supply, oxygen availability, or structural changes influence ocular metabolism in vivo.

Macular microcirculation characteristics in Parkinson's disease evaluated by OCT-Angiography: a literature review

PURPOSE

Given the fact that retina may provide a window into the central nervous system, there has been interest in identifying retinal biomarkers as predicting factors of pathological processes in neurodegenerative disorders. Emerging evidence has suggested that macular microcirculation changes in Parkinson disease (PD) may indicate the alterations of cerebral microvasculature. The use of Optical Coherence Tomography Angiography (OCT-A) has attracted significant attention in recent years as this technique offers a detailed analysis of the existence of changes at the macular capillary plexus.

METHODS

A detailed review of the literature was performed in PubMed until June 2021. We identified all papers referring to the alterations of the macular capillary plexus in PD using OCT-A.

RESULTS

A comprehensive update indicates that microvasculature alterations of the macular capillary plexus utilizing OCT-A may comprise useful biomarkers regarding the cerebral vasculature in PD. Since the available evidence is limited, additional studies are warranted to establish the OCT-A parameters as predicting factors in clinical practice.

CONCLUSIONS

A review of the existing literature sheds light on the microvasculature changes of the macular capillary plexus as seen on OCT-A in PD patients. The current article discusses notable aspects of key publications on the topic, highlights the importance of the potential long-term effectiveness of OCT-A biomarkers in PD and proposes the need for further future research.

Age-Related Retinal Changes in Wild-Type C57BL/6J Mice Between 2 and 32 Months

Purpose

The purpose of this study was to extend our understanding of how aging affects normal retina function and morphology in wild-type C57BL/6J mice, by analyzing electrophysiological recordings and in vivo and post mortem anatomy.

Methods

Electroretinograms (ERGs), spectral domain optical coherence tomography (SD-OCT), and confocal scanning laser ophthalmoscope (cSLO) in vivo images were obtained from mice between the ages of 2 and 32 months in four groups: group 1 (<0.5 years), group 2 (1.0-1.5 years), group 3 (1.5-2.0 years), and group 4 (>2.0 years). Afterward, mouse bodies and eyes were weighed. Eyes were stained with hematoxylin and eosin (H&E) and cell nuclei were quantified.

Results

With aging, mice showed a significant reduction in both a- and b-wave ERG amplitudes in scotopic and photopic conditions. Additionally, total retina and outer nuclear layer (ONL) thickness, as measured by SD-OCT images, were significantly reduced in older groups. The cSLO images showed an increase in auto-fluorescence at the photoreceptor-RPE interface as age increases. H&E cell nuclei quantification showed significant reduction in the ONL in older ages, but no differences in the inner nuclear layer (INL) or ganglion cell layer (GCL).

Conclusions

By using multiple age groups and extending the upper age limit of our animals to approximately 2.65 years (P970), we found that natural aging causes negative effects on retinal function and morphology in a gradual, rather than abrupt, process. Future studies should investigate the exact mechanisms that contribute to these gradual declines in order to discover pathways that could potentially serve as therapeutic targets.

Retinal microvascular complexity comparing mono- and multifractal dimensions in relation to cardiometabolic risk factors in a Middle Eastern population

PURPOSE

Metrics that capture changes in the retinal microvascular structure are relevant in the context of cardiometabolic disease development. The microvascular topology is typically quantified using monofractals, although it obeys more complex multifractal rules. We study mono- and multifractals of the retinal microvasculature in relation to cardiometabolic factors.

METHODS

The cross-sectional retrospective study used data from 3000 Middle Eastern participants in the Qatar Biobank. A total of 2333 fundus images (78%) passed quality control and were used for further analysis. The monofractal (D_f ) and five multifractal metrics were associated with cardiometabolic factors using multiple linear regression and were studied in clinically relevant subgroups.

RESULTS

D_f and multifractals are lowered in function of age, and D_f is lower in males compared to females. In models corrected for age and sex, D_f is significantly associated with BMI, insulin, systolic blood pressure, glycated haemoglobin (HbA1c), albumin, LDL and total cholesterol concentrations. Multifractals are negatively associated with systolic and diastolic blood pressure, glucose and the WHO/ISH cardiovascular risk score. D_f was higher, and multifractal curve asymmetry was lower in diabetic patients (HbA1c > 6.5%) compared to healthy individuals (HbA1c < 5.7%). Insulin resistance (insulin ≥ 23 mcU/mL) was associated with significantly lower D_f values.

CONCLUSION

One or more fractal metrics are in association with sex, age, BMI, systolic and diastolic blood pressure and biochemical blood measurements in a Middle Eastern population study. Follow-up studies aiming at investigating retinal microvascular changes in relation to cardiometabolic risk should analyse both monofractal and multifractal metrics for a more comprehensive microvascular picture.

Repeatability of Peripapillary Optical Coherence Tomography Angiography Parameters in Older Adults

Purpose:

This work assesses the intrasession repeatability of capillary perfusion density (CPD) and capillary flux index (CFI) measurements on peripapillary optical coherence tomography angiography (OCTA) in healthy eyes of older adults.

Methods:

In this cross-sectional study, healthy volunteers aged 50 years or older underwent 4.5 × 4.5 mm OCTA imaging centered on the optic nerve head using Zeiss Cirrus HD-5000 AngioPlex (Carl Zeiss Meditec). Two consecutive images were acquired in the same eye during a single study session. CPD and CFI were assessed using AngioPlex Software (version 11.0.0.29946) for the radial peripapillary capillary plexus (average over whole scan area) and 4 quadrants (superior, inferior, temporal, and nasal). CPD and CFI repeatability was assessed by intraclass correlation (ICC), mean interocular differences using 2-tailed t test, and association with age using generalized estimating equations.

Results:

A total of 150 images were acquired from 75 eyes of 47 patients. For CPD, ICC results ranged from 0.7160 (nasal CPD) to 0.9218 (average CPD). For CFI, ICC results ranged from 0.6167 (temporal CFI) to 0.8976 (inferior CFI). Temporal CFI was significantly different between right and left eyes of the same patient ( P = .03). CPD and CFI decreased with age in all analyses (average CPD β coefficient –0.00172, P < .001; average CFI β coefficient −0.00278, P < .001).

Conclusions:

Moderate to good repeatability was observed for most peripapillary OCTA metrics; temporal measurements were least repeatable for CPD and CFI. Peripapillary CPD and CFI decrease with age even beyond the fifth decade in healthy older adults.

Retinal microvascular parameters are not significantly associated with mild cognitive impairment in the Northern Ireland Cohort for the Longitudinal Study of Ageing

BACKGROUND

The retinal and cerebral microvasculature share similar embryological origins and physiological characteristics. Improved imaging technologies provide opportunistic non-invasive assessment of retinal microvascular parameters (RMPs) against cognitive outcomes. We evaluated baseline measures for associations between RMPs and mild cognitive impairment (MCI) from participants of the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA).

METHODS

RMPs (central retinal arteriolar / venular equivalents, arteriole to venular ratio, fractal dimension and tortuosity) were measured from optic disc centred fundus images and analysed using semi-automated software. Associations between RMPs and MCI were assessed by multivariable logistic regression with adjustment for potential confounders including age, sex, alcohol consumption, smoking status, educational attainment, physical activity, cardiovascular disease (CVD), hypertension, mean arterial blood pressure, triglycerides, diabetes, body mass index, and high density lipoprotein levels. P < 0.05 was considered statistically significant.

RESULTS

Data were available for 1431 participants, of which 156 (10.9%) were classified with MCI defined by a Montreal Cognitive Assessment (MoCA) score ≤ 26, with subjective cognitive decline, in the absence of depression or problems with activities of daily living. Participants had a mean age of 62.4 ± 8.5 yrs. and 52% were female. As expected, individuals with MCI had a lower MoCA score than those without (23.5 ± 2.6 versus 26.3 ± 2.7, respectively), were more likely to be female, have a lower level of educational attainment, be less physically active, more likely to have CVD, have higher levels of triglycerides and lower levels of high density lipoprotein. No significant associations between RMPs and MCI were detected in unadjusted, minimally adjusted or fully adjusted regression models or subsequent sensitivity analyses.

CONCLUSION

Previous studies have reported both increased retinal venular calibre and reduced fractal dimension in association with mild cognitive impairment. Our study failed to detect any associations between RMPs and those individuals at an early stage of cognitive loss in an older community-based cohort.

Association of reduced retinal arteriolar tortuosity with depression in older participants from the Northern Ireland Cohort for the Longitudinal Study of Ageing

INTRODUCTION

The retina shares similar anatomical and physiological features with the brain and subtle variations in retinal microvascular parameters (RMPs) may reflect similar vascular variation in the brain. The aim of this study was to assess associations between RMPs and measures of depression in the Northern Ireland Cohort for the Longitudinal Study of Ageing.

METHODS

RMPs (arteriolar and venular caliber, fractal dimension and tortuosity) were measured from optic disc centred fundus images using semi-automated software. Depression was characterised by the Centre for Epidemiologic Studies Depression Scale (CES-D) in the absence of mild cognitive impairment or use of anti-depressive medications. Associations between depression and RMPs were assessed by regression analyses with adjustment for potential confounders.

RESULTS

Data were available for 1376 participants of which 113 (8.2%) and 1263 (91.8%) were classified with and without depression. Participants had a mean age of 62.0 ± 8.4 yrs., 52% were female, and 8% were smokers. Individuals with depression had a higher CES-D score than those without (22.0 ± 6.2 versus 4.4 ± 3.9). Lower values of arteriolar tortuosity were significantly associated with depression, before and after adjustment for potential confounders (odds ratio = 0.79; 95% confidence intervals: 0.65, 0.96; P = 0.02).

CONCLUSION

Decreased retinal arteriolar tortuosity, a measure of the complexity of the retinal microvasculature was associated with depression in older adults independent of potential confounding factors. Retinal measures may offer opportunistic assessment of microvascular health associated with outcomes of depression.

Retinal vascular tortuosity: Mechanisms and measurements

Retinal vessel tortuosity has been used in the diagnosis and management of different clinical situations. Notwithstanding, basic concepts, standards and tools of measurement, reliable normative data and clinical applications have many gaps or points of divergence. In this review we discuss triggering causes of retinal vessel tortuosity and resources used to assess and quantify it, as well as current limitations.

Angiography with optical coherence tomography as a biomarker in multiple sclerosis

PURPOSE

To investigate superficial retinal microvascular plexuses detected by optical coherence tomography angiography (OCT-A) in multiple sclerosis (MS) subjects and compare them with healthy controls.

METHODS

A total of 92 eyes from 92 patients with relapsing-remitting MS and 149 control eyes were included in this prospective observational study. OCT-A imaging was performed using Triton Swept-Source OCT (Topcon Corporation, Japan). The vessel density (VD) percentage in the superficial retinal plexus and optic disc area (6 x 6 mm grid) was measured and compared between groups.

RESULTS

MS patients showed a significant decrease VD in the superior (p = 0.005), nasal (p = 0.029) and inferior (p = 0.040) parafoveal retina compared with healthy subjects. Patients with disease durations of more than 5 years presented lower VD in the superior (p = 0.002), nasal (p = 0.017) and inferior (p = 0.022) parafoveal areas compared with healthy subjects. Patients with past optic neuritis episodes did not show retinal microvasculature alterations, but patients with an EDSS score of less than 3 showed a significant decrease in nasal (p = 0.024) and superior (p = 0.006) perifoveal VD when compared with healthy subjects.

CONCLUSIONS

MS produces a decrease in retinal vascularization density in the superficial plexus of the parafoveal retina. Alterations in retinal vascularization observed in MS patients are independent of the presence of optic nerve inflammation. OCT-A has the ability to detect subclinical vascular changes and is a potential biomarker for diagnosing the presence and progression of MS.

Retinal biomarkers for Alzheimer's disease and vascular cognitive impairment and dementia (VCID): implication for early diagnosis and prognosis

Cognitive impairment and dementia are major medical, social, and economic public health issues worldwide with significant implications for life quality in older adults. The leading causes are Alzheimer's disease (AD) and vascular cognitive impairment/dementia (VCID). In both conditions, pathological alterations of the cerebral microcirculation play a critical pathogenic role. Currently, the main pathological biomarkers of AD-β-amyloid peptide and hyperphosphorylated tau proteins-are detected either through cerebrospinal fluid (CSF) or PET examination. Nevertheless, given that they are invasive and expensive procedures, their availability is limited. Being part of the central nervous system, the retina offers a unique and easy method to study both neurodegenerative disorders and cerebral small vessel diseases in vivo. Over the past few decades, a number of novel approaches in retinal imaging have been developed that may allow physicians and researchers to gain insights into the genesis and progression of cerebromicrovascular pathologies. Optical coherence tomography (OCT), OCT angiography, fundus photography, and dynamic vessel analyzer (DVA) are new imaging methods providing quantitative assessment of retinal structural and vascular indicators-such as thickness of the inner retinal layers, retinal vessel density, foveal avascular zone area, tortuosity and fractal dimension of retinal vessels, and microvascular dysfunction-for cognitive impairment and dementia. Should further studies need to be conducted, these retinal alterations may prove to be useful biomarkers for screening and monitoring dementia progression in clinical routine. In this review, we seek to highlight recent findings and current knowledge regarding the application of retinal biomarkers in dementia assessment.

Normative Database of Peripapillary Vessel Density Measured by Optical Coherence Tomography Angiography and Correlation Study

Purpose: To provide a normative data set of swept-source optical coherence tomography angiography (SS-OCTA) peripapillary vessel density (VD) measurements and assess correlations with age, gender, disc area and axial length (AL). Material and Methods: This was an observational cross-sectional study conducted on 346 right eyes of healthy subjects. Peripapillary SS-OCTA VD measurements were obtained in the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) in all four quadrants using the Triton device (Topcon, Nagoya, Japan). AL measurements were made by optical biometry. Results: Mean participant age was 37.7 ± 19.8 years (range 5- 83), AL was 23.9 ± 1.3 mm (21-27), and 59% were women. Mean VDs for all quadrants were 57.2 ± 5.7% for SCP (52.4 ± 4.0% - 62.1 ± 4.2%), 46.3 ± 6.5% for DCP (41.9 ± 5.8% - 49.7 ± 4.8%) and 60.8 ± 7.4% for CC (53.4 ± 5.8% - 65.7 ± 5.5%). Negative correlation was detected between SCP VD and age (R = -0.264; P < .001), while correlation between DCP densities and age was positive (R = 0.202; P = .002). No associations were detected between peripapillary VD and gender (P ≥ 0.087) and negative correlation was found with AL and disc area only in the CC (P ≤ 0.004). In a subgroup analysis of 33 individuals, we noted no differences in VD between fellow eyes (P ≥ 0.139). Conclusion: Peripapillary VD showed wide individual variation when measured with the Triton SS-OCTA in the different retinal plexuses and CC. While correlations were observed with age, no relationships emerged with gender and only CC showed negative correlation with AL and disc area.