Application of Optical Coherence Tomography in the Detection and Classification of Cognitive Decline

Evaluation of the relationship between FDG-PET hypometabolism and retinal layer thickness in patients with Alzheimer's disease

We aimed to investigate the diagnostic value of Optical coherence tomography (OCT) in Alzheimer's disease (AD) and to assess the correlation between OCT and fluorodeoxyglucose (FDG)-positron emission tomography (PET) which shows high diagnostic agreement with findings from postmortem histopathology-the gold standard method. Patients who were diagnosed with AD-related dementia were selected for the study. Patients with a mini mental test (MMT) score between 18 and 23 were included in the study (n = 31). Volunteers with MMT ≥ 28 and no cognitive impairment were included in the study as the control group (n = 31). OCT imaging was performed in the patient and control groups after detailed ophthalmological examinations including visual acuity and intraocular pressure measurements. Brain glucose metabolism measurement was performed using 18 F-FDG PET/computed tomography. When adjusted for age and sex, mean retinal nerve fiber layer thickness (RNFL) thickness showed a significant difference between groups and the RNFL thickness in the superior temporal and superior nasal quadrants in AD-related mild dementia group showed a significant difference (p < 0.05). Furthermore, only the RNFL thickness in the inferior nasal quadrant of the right eye showed a significant difference between the groups (p = 0.016). It is thought that OCT is a promising imaging method in the elderly population due to its low-cost, non-invasive and easily applicability, and therefore, it may contribute in the future as a tool in the periodic follow-up of patients diagnosed with AD.

Non-Invasive Tools in Perioperative Stroke Risk Assessment for Asymptomatic Carotid Artery Stenosis with a Focus on the Circle of Willis

This review aims to explore advancements in perioperative ischemic stroke risk estimation for asymptomatic patients with significant carotid artery stenosis, focusing on Circle of Willis (CoW) morphology based on the CTA or MR diagnostic imaging in the current preoperative diagnostic algorithm. Functional transcranial Doppler (fTCD), near-infrared spectroscopy (NIRS), and optical coherence tomography angiography (OCTA) are discussed in the context of evaluating cerebrovascular reserve capacity and collateral vascular systems, particularly the CoW. These non-invasive diagnostic tools provide additional valuable insights into the cerebral perfusion status. They support biomedical modeling as the gold standard for the prediction of the potential impact of carotid artery stenosis on the hemodynamic changes of cerebral perfusion. Intraoperative risk assessment strategies, including selective shunting, are explored with a focus on CoW variations and their implications for perioperative ischemic stroke and cognitive function decline. By synthesizing these insights, this review underscores the potential of non-invasive diagnostic methods to support clinical decision making and improve asymptomatic patient outcomes by reducing the risk of perioperative ischemic neurological events and preventing further cognitive decline.

Assessment of metacognition and retinal optical coherence tomography findings in shift workers

It is known that working in the shift system, especially the night shift, affects physical, mental, and social well-being. We investigated the changes in the inner retinal layers and choroidal layer of the eyes of nurses working night and day shifts using optical coherence tomography (OCT). We also explored the effect of night shift work on metacognition and the relationships between these variables. A total of 79 nurses participated in the study, of whom 40 worked night shifts. The researcher gave the participants sociodemographic information and the Metacognition Questionnaire-30 (MCQ-30) form. Retinal nerve fiber layer (RNFL) thickness, ganglion cell layer (GCL) thickness, inner nuclear layer (INL) thickness, inner plexiform layer (IPL) thickness, central macular thickness (CMT), and subfoveal choroidal thickness (SFCT) were measured with OCT. It was found that the level of metacognitive activity associated with cognitive confidence was higher (p = 0.044) for nurses who worked night shifts and that the level of metacognitive activity associated with cognitive awareness was lower (p = 0.015) for nurses who worked night shifts. RNFL-nasal superior (NS) thickness was lower in night shift workers than the day shift group (p = 0.017). Our study revealed significant relationships between metacognition and the OCT findings among night and day shift workers. Our study revealed that RNFL measurements and metacognitive activity may differ and there may be a relationship between these parameters in nurses who work shifts. Further research is needed to investigate the long-term effects of night shift work on retinal health.

The association of cobalturia with cobaltism symptoms a prospective blinded study of 229 post-arthroplasty patients

INTRODUCTION

Cobalt is a mitochondrial toxin, clinical cobaltism manifests with constitutional, neurologic, and cardiovascular symptomatology. Cobalt's severe toxidrome is known through case reports from extreme wear or corrosion of cobalt-chromium arthroplasty components. However, the spectrum and epidemiology of orthopedic-implant cobaltism and its relationship to duration and degree of cobalt exposure are not well defined.

METHODS

The relationship of urine-cobalt concentration and duration of exposure to cobalt-chromium joint implants and cobaltism symptomatology were prospectively studied in 229 patients. Subjects received a Cobaltism-Symptom-Inventory-Score (CSIS) based on a protocolized interview and examination followed by a spot urine-cobalt measurement.

RESULTS

129 (56%) subjects were cobalturic (urine-cobalt ≥1.0 ppb). 122 (53%) subjects had a CSIS of >2, this status significantly associates with cobalturia. Median [IQR] urine-cobalt in the subjects with a CSIS >2 was 4.1[1.1-17.0] ppb compared to 0.5[0.5-1.4] ppb in subjects with CSIS ≤ 2. Cobalturia has a sensitivity of 0.69, a specificity of 0.77, and a positive predictive value of 0.74 for a CSIS of >2. The product of years-exposed to a cobalt-chromium implant and urine-cobalt by quartiles significantly positively associates with the Cobaltism-Symptom-Inventory-Score.

CONCLUSION

A urine-cobalt of ≥1 ppb likely indicates adverse systemic exposure to orthopedic-implant generated cobalt. Cobaltism severity as quantified by the CSIS significantly correlates with the product of spot urine-cobalt concentration and years-exposed to a cobalt-chromium orthopedic-implant indicating a dose-response relationship. Medical provider and public awareness of orthopedic-implant cobaltism is vital because tens-of-millions are at-risk and early cobaltism is reversible. Further use of cobalt-chromium orthopedic-implants should be questioned given cobaltism becomes clinically apparent at a spot urine-cobalt of 1 ppb or greater. Monitoring of patients with high-risk cobalt-chromium orthopedic-implants appears to be indicated.

Fairness and generalizability of OCT normative databases: a comparative analysis

PURPOSE

In supervised Machine Learning algorithms, labels and reports are important in model development. To provide a normality assessment, the OCT has an in-built normative database that provides a color base scale from the measurement database comparison. This article aims to evaluate and compare normative databases of different OCT machines, analyzing patient demographic, contrast inclusion and exclusion criteria, diversity index, and statistical approach to assess their fairness and generalizability.

METHODS

Data were retrieved from Cirrus, Avanti, Spectralis, and Triton's FDA-approval and equipment manual. The following variables were compared: number of eyes and patients, inclusion and exclusion criteria, statistical approach, sex, race and ethnicity, age, participant country, and diversity index.

RESULTS

Avanti OCT has the largest normative database (640 eyes). In every database, the inclusion and exclusion criteria were similar, including adult patients and excluding pathological eyes. Spectralis has the largest White (79.7%) proportionately representation, Cirrus has the largest Asian (24%), and Triton has the largest Black (22%) patient representation. In all databases, the statistical analysis applied was Regression models. The sex diversity index is similar in all datasets, and comparable to the ten most populous contries. Avanti dataset has the highest diversity index in terms of race, followed by Cirrus, Triton, and Spectralis.

CONCLUSION

In all analyzed databases, the data framework is static, with limited upgrade options and lacking normative databases for new modules. As a result, caution in OCT normality interpretation is warranted. To address these limitations, there is a need for more diverse, representative, and open-access datasets that take into account patient demographics, especially considering the development of supervised Machine Learning algorithms in healthcare.

Association of Optic Nerve Head and Macular Optical Coherence Tomography Measures With Glaucoma-Related Disability

PRCIS

Optical coherence tomography (OCT) estimated retinal nerve fiber layer (RNFL) thickness associated with glaucoma-related disability independent of the visual field (VF) damage and thus may provide additional patient-relevant disability information beyond what is captured by standard VF testing.

PURPOSE

To examine whether OCT metrics [peripapillary RNFL thickness and macular ganglion cell/inner plexiform layer (GCIPL) thickness] are associated with quality of life (QoL) measures and additional disability metrics, and whether these associations are independent of VF damage.

METHODS

In this cross-sectional study, 156 patients with glaucoma or suspected glaucoma received VF testing and OCT scans to measure RNFL and GCIPL thickness. QoL was assessed using the Glaucoma Quality-of-Life 15 and additional disability measures including fear of falling, reading speed, and steps per day were assessed. Multivariable regression models adjusting for relevant covariates tested whether RNFL or GCIPL thickness from the less-impaired eye were associated with disability measures and whether associations were independent of VF damage.

RESULTS

Greater VF damage is associated with worse QoL (95% CI=0.4-1.4; P <0.001) and slower reading speed (CI=-0.06 to -0.02; P <0.001). Lower RNFL and GCIPL thicknesses were associated with lower QoL scores, but not with QoL scores or other disability metrics after correcting for VF damage. However, post hoc analyses in patients with better eye thicknesses between 55 and 75 µm demonstrated associations between lower RNFL thickness and worse QoL (CI=-2.2 to -0.1; P =0.04) and greater fear of falling (CI=-6.1 to -0.4; P =0.03) even after accounting for VF damage. No such associations were observed for GCIPL thickness.

CONCLUSIONS

OCT RNFL, but not GCIPL, thickness is associated with multiple disability measures independent of VF damage severity.

Association of Central Retinal Arteriolar and Venular Equivalents with Brain-aging and Macular Ganglion Cell-inner Plexiform Layer Thickness

INTRODUCTION

Neurodegeneration and cognitive decline in aging are growing public health concerns. This study investigates associations between central retinal arteriolar and venular equivalents (CRAE, CRVE) and brain-aging, a sensory and cognitive test composite measure, and macular ganglion cell-inner plexiform layer (mGCIPL) thickness, a biomarker of neurodegeneration.

METHODS

Beaver Dam Offspring Study (BOSS) participants are adult children (baseline (2005-2008) age 21-84 years) of the population-based Epidemiology of Hearing Loss Study participants. Follow-up occurred every 5 years. In 2010-2013, fundus photographs were used to measure retinal vessels. A brain-aging score was constructed by principal component analysis using sensorineural and cognitive data. Associations between incident brain-aging and vessel measures were investigated using logistic regression. Associations between CRAE and CRVE and mGCIPL thickness, measured in 2015-2017, were also investigated.

RESULTS

Participants (N = 2381; mean age: 53.9 years (SD = 9.8); 54% women) had a mean CRAE and CRVE of 148.8 µm (SD = 14.5) and 221.7 µm (SD = 20.7), respectively. Among those without ocular conditions, wider CRAE was associated with decreased 5-year brain-aging risk (33% per SD CRAE increase). Both vessel measures were independently associated with mGCIPL thickness. The mGCIPL thickness increased by approximately 1.7 µm and 2.0 µm per SD increase in CRAE and CRVE, respectively.

DISCUSSION

The association of CRAE with incident brain-aging indicates its potential use as a screening tool among those without eye disease. The associations between CRAE and CRVE and mGCIPL thickness indicate narrower vasculature could affect neuronal health. These associations point to potential usefulness of retinal vessel measurements to identify people at higher risk of sensorineural declines and neurodegeneration.

An Association Between Large Optic Cupping and Total and Regional Brain Volume: The Women's Health Initiative

PURPOSE

To investigate the relationships between optic nerve cupping and total and regional brain volumes.

DESIGN

Secondary analysis of randomized clinical trial data.

METHODS

Women 65 to 79 years of age without glaucoma with cup-to-disc ratio (CDR) measurements from the Women's Health Initiative (WHI) Sight Examination study and magnetic resonance imaging (MRI)-based total and regional brain volumes from the WHI Memory Study MRI-1 were included. Large CDR was defined as 0.6 or greater in either eye. Generalized estimating equation models were used to account for intra-brain correlations between the right and left sides. The final analysis was adjusted for demographic and clinical characteristics and for total brain volume (for regional analyses).

RESULTS

Final analyses included 471 women, with the mean age ± SD was 69.2 ± 3.6 years; 92.8% of the subjects were white. Of 471 women, 34 (7.2%) had large CDR. Controlling for total brain volume and for demographic and clinical characteristics, lateral ventricle volume was 3.01 cc larger for subjects with large CDR compared to those without large CDR (95% CI = 0.02 to 5.99; P = .048). Furthermore, frontal lobe volume was 4.78 cc lower for subjects with large CDR compared to those without (95% CI = -8.71, -0.84; P = 0.02), and occipital lobe volume was 1.86 cc lower for those with large CDR compared to those without (95% CI = -3.39, -0.3; P =.02).

CONCLUSIONS

Our analysis suggests that in women aged 65 years or more, large CDR is associated with lower relative total brain volume and absolute regional volume in the frontal and occipital lobes. Enlarged CDR in individuals without glaucoma may represent a sign of optic nerve and brain aging, although more longitudinal data are needed.

Optical coherence tomography in neurodegenerative disorders

ABSTRACT Structural imaging of the brain is the most widely used diagnostic tool for investigating neurodegenerative diseases. More advanced structural imaging techniques have been applied to early or prodromic phases, but they are expensive and not widely available. Therefore, it is highly desirable to search for noninvasive, easily accessible, low-cost clinical biomarkers suitable for large-scale population screening, in order to focus on making diagnoses at the earliest stages of the disease. In this scenario, imaging studies focusing on the structures of the retina have increasingly been used for evaluating neurodegenerative diseases. The retina shares embryological, histological, biochemical, microvascular and neurotransmitter similarities with the cerebral cortex, thus making it a uniquely promising biomarker for neurodegenerative diseases. Optical coherence tomography is a modern noninvasive imaging technique that provides high-resolution two-dimensional cross-sectional images and quantitative reproducible three-dimensional volumetric measurements of the optic nerve head and retina. This technology is widely used in ophthalmology practice for diagnosing and following up several eye diseases, such as glaucoma, diabetic retinopathy and age-related macular degeneration. Its clinical impact on neurodegenerative diseases has raised enormous interest over recent years, as several clinical studies have demonstrated that these diseases give rise to reduced thickness of the inner retinal nerve fiber layer, mainly composed of retinal ganglion cells and their axons. In this review, we aimed to address the clinical utility of optical coherence tomography for diagnosing and evaluating different neurodegenerative diseases, to show the potential of this noninvasive and easily accessible method.

Past, present and future role of retinal imaging in neurodegenerative disease

Retinal imaging technology is rapidly advancing and can provide ever-increasing amounts of information about the structure, function and molecular composition of retinal tissue in humans in vivo. Most importantly, this information can be obtained rapidly, non-invasively and in many cases using Food and Drug Administration-approved devices that are commercially available. Technologies such as optical coherence tomography have dramatically changed our understanding of retinal disease and in many cases have significantly improved their clinical management. Since the retina is an extension of the brain and shares a common embryological origin with the central nervous system, there has also been intense interest in leveraging the expanding armamentarium of retinal imaging technology to understand, diagnose and monitor neurological diseases. This is particularly appealing because of the high spatial resolution, relatively low-cost and wide availability of retinal imaging modalities such as fundus photography or OCT compared to brain imaging modalities such as magnetic resonance imaging or positron emission tomography. The purpose of this article is to review and synthesize current research about retinal imaging in neurodegenerative disease by providing examples from the literature and elaborating on limitations, challenges and future directions. We begin by providing a general background of the most relevant retinal imaging modalities to ensure that the reader has a foundation on which to understand the clinical studies that are subsequently discussed. We then review the application and results of retinal imaging methodologies to several prevalent neurodegenerative diseases where extensive work has been done including sporadic late onset Alzheimer's Disease, Parkinson's Disease and Huntington's Disease. We also discuss Autosomal Dominant Alzheimer's Disease and cerebrovascular small vessel disease, where the application of retinal imaging holds promise but data is currently scarce. Although cerebrovascular disease is not generally considered a neurodegenerative process, it is both a confounder and contributor to neurodegenerative disease processes that requires more attention. Finally, we discuss ongoing efforts to overcome the limitations in the field and unmet clinical and scientific needs.

Optic Nerve Parameters and Cognitive Function in the Northern Finland Birth Cohort Eye Study

PURPOSE

The optic nerve head (ONH) is a part of the brain that can be easily studied through the transparent medium of the eye. We explored the relationship between the properties of the optic nerve head, the retinal nerve fiber layer (RNFL) and cognitive function.

METHODS

Participants of the Northern Finland Birth Cohort (NFBC) 1966 underwent an ophthalmic and cognitive assessment after randomization at age 46. The ophthalmological parameters obtained were the disc area and the neuroretinal rim volume of the ONH and the average RNFL thickness. The surrogates used for cognitive function were the paired associates learning test (PAL), level of education, grade point average (GPA) and Humphrey 24-2 perimetric test time (HFA). We did exploratory research between the ophthalmological parameters and the surrogates for cognition and the correlations between the surrogates for cognition.

RESULTS

We found that a larger disc area was associated with a higher level of education, faster accomplishment of the HFA (R = -0.065) but a lower GPA (R = -0.084). An increase in neuroretinal rim volume was associated with fewer errors in the PAL test (R = -0.056), higher level of education, higher GPA (R = 0.072) and faster accomplishment of the HFA (R = -0.047). A thicker RNFL was associated with faster accomplishment of the HFA (R = -0.047).

CONCLUSION

We were able to find statistically significant associations between the parameters of the optic nerve head, the RNFL and cognition in the NFBC Eye study. However, the correlations were negligible at best and of limited predictive value.

Relationship Between Alzheimer's Disease and Retinal Choroidal Thickness: A Cross-Sectional Study

BACKGROUND

The choroid is involved directly or indirectly in many pathological conditions such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS).

OBJECTIVE

The objective of this study was to investigate the association between retinal choroidal properties and the pathology of AD by determining choroidal thickness, hippocampus volume, cognitive functions, and plasma BACE1 activity.

METHODS

In this cross-sectional study, 37 patients with AD and 34 age-matched controls were included. Retinal choroidal thickness was measured via enhanced depth imaging optical coherence tomography. Hippocampal volume was measured via 3.0T MRI. Cognitive functions were evaluated using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog). Plasma BACE1 activity was analyzed using a fluorescence substrate-based plasma assay, and regression model were to analyze the data.

RESULTS

Retinal choroidal thickness was significantly thinner in the AD group than in the control group [(114.81±81.30) μm versus (233.79±38.29) μm, p < 0.05]. Multivariable regression analysis indicated that the ADAS-cog scores (β=-0.772, p = 0.000) and age (β=-0.176, p = 0.015) were independently associated with choroidal thickness. The logistic regression model revealed that the subfoveal choroidal thickness was a significant predictor for AD (OR = 0.984, 95% CI: 0.972-0.997).

CONCLUSION

There was a general tendency of choroid thinning as the cognitive function declined. Although choroidal thickness was not a potential indicator for early stage AD, it was valuable in monitoring AD progression.

Retinal thickness as a potential biomarker in patients with amyloid-proven early- and late-onset Alzheimer's disease

Introduction

Retinal thickness measured with optical coherence tomography has been proposed as a noninvasive biomarker for Alzheimer's disease (AD). We therefore measured retinal thickness in well-characterized AD and control participants, considering ophthalmological confounders.

Methods

We included 57 amyloid-proven AD cases and 85 cognitively normal, amyloid-negative controls. All subjects underwent retinal thickness measurements with spectral domain optical coherence tomography and an ophthalmological assessment to exclude ocular disease.

Results

Retinal thickness did not discriminate cases from controls, including stratified analyses for early- versus late-onset AD. We found significant associations between macular thickness and global cortical atrophy [β -0.358; P = .01] and parietal cortical atrophy on magnetic resonance imaging [β -0.371; P < .01] in AD cases.

Discussion

In this study, representing the largest optical coherence tomography cohort with amyloid-proven AD cases, we show that retinal thickness does not discriminate AD from controls, despite evident changes on clinical, neuroimaging, and CSF measures, querying the use of retinal thickness measurements as an AD biomarker.

An Association Between Large Optic Nerve Cupping and Cognitive Function

PURPOSE

To determine if a larger cup-to-disc ratio is associated with poor cognitive function in postmenopausal women without glaucoma or ocular hypertension.

METHODS

We used data from the Women's Health Initiative (WHI) hormone trial, originally designed to test effects of hormone therapy (HT) on various health outcomes. Large cup-to-disc ratio was defined as greater than 0.6 in either eye based on stereoscopic optic nerve photographs. Global cognitive function was assessed annually by Modified Mini-Mental State Examination (3MSE) in the WHI Memory Study. Exclusions were no information on optic nerve grading; no 3MSE scores at the time of the eye examination, ocular hypertension (intraocular pressure >23 mm Hg, Goldmann applanation tonometry), or glaucoma medication use. A generalized linear model for log-transformed 3MSE scores was used for determining the association between large cup-to-disc ratio and 3MSE scores, adjusting for age, race, diabetes, body mass index, cardiovascular disease, smoking, HT randomization, education, and diabetic retinopathy.

RESULTS

Analyses included 1636 women (mean age ± standard deviation, 69.57 ± 3.64 years; 90.39% white). Of those, 122 women had large cup-to-disc ratio. The mean 3MSE scores in women with vs without large cup-to-disc ratio were 95.4 ± 6 vs 96.6 ± 5. In the adjusted model, women with large cup-to-disc ratio had statistically significantly lower 3MSE scores, compared with those without large cup-to-disc ratio, yielding the predicted mean difference in 3MSE scores of 0.75 with a standard error of 0.05 units (P = .04).

CONCLUSIONS

Postmenopausal women who had large cup-to-disc ratio without glaucoma or ocular hypertension exhibited lower global cognitive function. Further investigation is warranted. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

[Optical coherence tomography angiography in neuronal diseases : Preliminary findings]

BACKGROUND

Optical coherence tomography angiography (OCTA) enables a noninvasive detailed imaging of retinal and choroidal vessels of the fundus. In neuronal diseases changes in retinal structures can be imaged and measured with OCT and OCTA.

OBJECTIVE

Can OCTA be used in neuronal diseases?

MATERIAL AND METHODS

Evaluation of recent scientific articles and studies extracted from Medline on the topic of OCTA and neuronal diseases.

RESULTS

It could be shown that Alzheimer type dementia, Parkinson's disease, multiple sclerosis. cerebral infarction and CADASIL are neuronal diseases with rarification of retinal vessels and atrophy of the retinal layers in the ocular fundus.

CONCLUSION

These findings are beyond all changes which can be appreciated with ophthalmoscopy and OCTA parameters could serve in the future as supplementary biomarkers for assessment of the retinal-neurovascular coupling in these diseases.

Principles of OCTA and Applications in Clinical Neurology

PURPOSE OF REVIEW

The article reviews the recent findings on the use of optical coherence tomography angiography (OCTA) in neurology.

RECENT FINDINGS

OCTA is a new addition to the powerful and complementary technology of the OCT. Due to its noninvasiveness, and reproducibility, it is possible to obtain high-resolution 3D images of the vessels of the human eye. As the vessels of the retina with the presence of endothelial cell's tight junctions resemble the brain vessels, it was hypothesized that the imaging of the retinal vessels might bring insight into brain vessels. OCTA has been effectively used to predict retinal vessel abnormalities in dementia, demyelization, optic disc neuropathies, and inherited degenerative diseases. Most common findings were decrease of vascular density and flow and an increase of avascular zones. Although OCTA is a relative new technology, recent studies show that it can be successfully applied in neurology.