Comparison of OCTA Factors in Patients With or Without Amyloid Pathology: A Prospective Study

Study Overview
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Brief Summary
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To compare alternation of retinal microcirculation within the macula and optic disc in patients with dementia, mild cognitive impairment (MCI), and cognitively healthy subjects who had positive amyloid biomarkers (Aβ +) or not, using optical coherence tomography angiography (OCTA).

Detailed Description
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Alzheimer disease dementia (ADD) is the most common neurodegenerative disease dementia in elderly population associated with the accumulation of beta-amyloid (Aβ) plaques and tau neurofibrillary tangles (NFTs). Diagnostic biomarkers reflecting underlying amyloid or tau pathology of ADD have actively been developed. Of these, amyloid or tau positron emission tomography (PET) imaging and cerebrospinal fluid (CSF) Aβ1-42 or phosphorylated tau are representative biomarkers for ADD. However, these tend to be expensive, invasive, or available only in a tertiary hospital or a specialized laboratory. Alternative biomarkers which are inexpensive, less invasive, and highly available could be needed. Patients with ADD commonly show visuospatial dysfunction which is mainly attributed to damage of parieto-occipital or temporo-occipital visual pathway. In addition, previous studies using optical coherence tomography (OCT) which is a useful tool measuring retinal nerve fiber layer thickness (RNFLT), macula ganglion cell/inner plexiform layer thickness (GC/IPLT) reported impaired pregeniculate afferent visual pathway, for example, reduction of RNFLT and loss of retinal ganglionic cells (RGCs) in patients with ADD. The retina and brain have the same embryological origin. These were branched off from the forebrain, so the brain and retina have similar anatomic and physiologic traits of the vasculature. In line with this, several studies using laser doppler ultrasonography, or retinal function imager (RFI) revealed narrowed central retinal vein and decreased its blood velocity, or low blood flow rate of retinal arterioles and venules in patients with mild cognitive impairment (MCI) and ADD. The authors suggested that in patients with ADD, accumulation of Aβ in the vessel walls could cause disruption of basement membrane and endothelium, leading to the decreased vascular lumen and density of retinal vessel. Indeed, postmortem study revealed accumulated Aβ inside or around RGCs in AD. OCTA can clearly visualize not only the specific layers of retinal vasculatures, including superficial, middle, and deep capillary plexuses, but also choroidal vessels with a high resolution and in a reproducible manner, without contrast agent. A few prior studies using OCTA reported enlarged foveal avascular zone (FAZ) and decrease of retinal vascular density and choroidal thickness in ADD or MCI compared to controls. On the other hand, the others showed no differences in FAZ area and vessel density between them. In this study, the investigators first evaluated structural and microvascular changes of retina and the microvascular change of macula and optic disc in patients with clinically diagnosed ADD, MCI and cognitively normal controls using OCT and OCTA. Then, to investigate whether impaired pregeniculate visual pathway is truly associated with underlying amyloid pathology, the investigators further investigated those OCT and OCTA parameters in each subgroup with positive or negative amyloid biomarker.

Official Title
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Comparison of Optical Coherence Tomography Angiographic Factors of Macula and Optic Disc in Patients With or Without Amyloid Pathology: A Prospective Study

Conditions
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Alzheimer Disease, Amyloid Angiopathy, Macular Ischemia, Dementia, Mild Cognitive Impairment

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Clinical and pathologic diagnosis of ADD or MCI as well as cognitively unimpaired control (CU) from the Neurologic Clinic of Pusan National University Hospital Exclusion Criteria: Patient not within the ages of 50-90 years old Patient with glaucoma, macular degeneration, retinal vascular disease including diabetic retinopathy, retinal vein occlusion Intraocular pressure (IOP) ≥ 21 mmHg Dense corneal or ocular media opacity History of ocular trauma or associated ocular disease Astigmatism ≥ 3.0 diopter or spherical equivalent ≥ 6.0 diopter Best corrected visual acuity (BCVA) < 20/40 Any ocular surgery except uncomplicated cataract extraction Uncontrolled hypertension and diabetes

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 90 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Dementia<br>Patients with Alzheimer disease dementia (ADD) fulfilled the NIA-AA core clinical criteria for probable ADD and Aβ positive according to ATN classification scheme. Aβ positive refers to Aβ pathology (CSF Aβ1-42 < 631.8 pg/ml or positive amyloid deposits on 18F-flutemetamol PET by visual inspection). | |
| MCI (Mild cognitive impairment)<br>Patients with mild cognitive impairment (MCI) met the Petersen's criteria. | |
| CU (Cognitively unimpaired control)<br>CU consisted of cognitively unimpaired subjects whose cognition (as defined by the Seoul Neuropsychological Screening Battery (SNSB)) was within normal limits. | |
| Aβ positive<br>Aβ positive refers to Aβ pathology (CSF Aβ1-42 < 631.8 pg/ml or positive amyloid deposits on 18F-flutemetamol PET by visual inspection). | |
| Aβ negative<br>Aβ negative was within normal limits. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| SD-OCT imaging | Measuring macular GC/IPLT (μm) and cimcumpapillary RNFLT (μm). The average, minimum, and 6 sectoral (superotemporal, superior, superonasal, inferonasal, inferior, and inferotemporal) GC/IPLT (μm) values are obtained. The average, 4 sectoral (temporal, superior, nasal, and inferior), and 12 clock-hour circumpapillary RNFLT (μm) are obtained. Multiple measurements will not be aggregated, but analyzed respectively. | Through study completion, measured at enrollment and analyzed from September 2019 to July 2021 | 
| SD-OCTA imaging | Acquiring microvasculature images of macular (6 × 6 mm^2 scan) and optic disc areas (4.5 × 4.5 mm^2 scan). The average vessel density (VD, mm/mm^2) and perfusion density (PD, %) were automatically measured in the Early Treatment of Diabetic Retinopathy Study (ETDRS) grid with values shown in the nine subfields, central, inner, outer and full region. The software calculated the area (mm^2), perimeter (mm), and circularity (defined as 4πA/P^2, where A was the area and P was the perimeter) of foveal avascular zone (FAZ). A circularity closer to 0 means an irregular shape, and closure to 1 indicates a circular shape. Multiple measurements will not be aggregated, but analyzed respectively. | Through study completion, measured at enrollment and analyzed from September 2019 to July 2021 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Diagnostic performance | Diagnostic performance of OCT and OCTA parameters according to underlying Aβpathology. Receiver operating characteristic (ROC) curves were drawn by plotting sensitivity against 1-specificity, and areas under ROC curves (AUCs) were used to evaluate the diagnostic performance of continuous OCT/OCTA variables. Ideal cut-off points were derived using the Youden index | Through study completion, analyzed from July 2021 to July 2022 | 
| Correlations | Correlations between MMSE score and all of OCT/OCTA parameters were expressed as Pearson's or Spearman's rank correlation coefficients to account for the normal or non-normal distribution of the parameters, respectively. OCT/OCTA parameters including as follows; macular GC/IPLT (μm): average, minimum, and 6 sectoral (superotemporal, superior, superonasal, inferonasal, inferior, and inferotemporal) GC/IPLT cimcumpapillary RNFLT (μm): verage, 4 sectoral (temporal, superior, nasal, and inferior), and 12 clock-hour circumpapillary RNFLT Macular vessel density (VD, mm/mm^2) & perfusion density (PD, %) : VDs and PDs of central, parafoveal (nasal, temporal, superior, inferior), perifoveal (nasal, temporal, superior, inferior), and total Optic disc perfusion density (%) and flux index (from 0 to 1) : nasal, temporal, superior, inferior | Through study completion, analyzed from July 2021 to July 2022 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Alzheimer disease dementia, Mild cognitive impairment, Amyloid pathology, Optical coherence tomographic angiography