Tear Biomarkers and Alzheimer’s Disease

Abstract

Alzheimer’s disease (AD) is an age-related progressive neurodegenerative brain disorder that represents the most common type of dementia. It poses a significant diagnostic challenge that requires timely recognition and treatment. Currently, there is no effective therapy for AD; however, certain medications may slow down its progression. The discovery of AD biomarkers, namely, magnetic resonance imaging, positron emission tomography and cerebrospinal fluid molecules (amyloid-β and tau) has advanced our understanding of this disease and has been crucial for identifying early neuropathologic changes prior to clinical changes and cognitive decline. The close interrelationship between the eye and the brain suggests that tears could be an interesting source of biomarkers for AD; however, studies in this area are limited. The identification of biomarkers in tears will enable the development of cost-effective, non-invasive methods of screening, diagnosis and disease monitoring. In order to use tears as a standard method for early and non-invasive diagnosis of AD, future studies need to be conducted on a larger scale.

Liquid clues: tear film biomarkers unravelling Alzheimer’s mysteries

“…Recent advances in AD biomarkers include tear markers, which are non-invasive. Tears are non-invasive biological fluid, easy to collect and can be stored for extended periods, certain amount of diseases can be assessed using tear markers in place of other biomarkers, including keratoconus, Parkinson disease, cystic fibrosis and thyroid disease 10 . Studies show that diagnostic biomarkers such as Aß42 and p-tau, which are found in tears, are under investigation for their cost-effectiveness.…”

Advancements in Cerebrospinal Fluid Biosensors: Bridging the Gap from Early Diagnosis to the Detection of Rare Diseases

“…The TearAD study aimed to use tear fluid as a potential source of AD biomarkers. In previous reports, it was demonstrated that the AD biomarkers amyloid-beta and tau are measurable in tear fluid and are associated with disease severity and neurodegeneration [ 126 ]. This study aimed to validate the previous results in a larger cohort and evaluated the diagnostic accuracy of tear biomarkers when discriminating between individuals with and without neurodegeneration, as determined by hippocampal atrophy [ 126 ].…”

From Gut Microbiota to Brain Waves: The Potential of the Microbiome and EEG as Biomarkers for Cognitive Impairment

“…Additionally, many of these tests are associated with negative side effects such as radiation exposure from PET scans [68]. Finding a simple and non-invasive method that can be frequently administered for early AD or MCI diagnosis could provide an opportunity for those affected by AD to receive treatment that slows progression [68][69][70][71]. Furthermore, early detection biomarkers can be used to screen for individuals at a high risk of AD.…”