Alzheimer's disease (AD) is the most common neurodegenerative disease-causing dementia. The severity of symptoms determines the diagnosis of AD, although an accurate diagnosis can only be made postmortem. Neuropsychological testing is the «gold standard» for early diagnosis of AD, but is time-consuming, does not allow a complete diagnosis with complete accuracy, is highly dependent on the correctness of the tests, and is rather an adjunct to the examination of the patient. Lumbar puncture and positron emission tomography are not available for routine screening of the population. Because the eye is an extension of the central nervous system, the study of its changes may lead to the development of a number of non-invasive differential diagnostic tests to identify patients with AD at an early stage. In recent years, the advent of quantifiable high-resolution imaging techniques that are non-invasive, rapid, and widely available has opened up a new field of ocular-neural imaging. In this paper, we review current foreign and domestic studies of some ocular biomarkers and the methods that could potentially be used in the early diagnosis of Alzheimer's disease.

Alzheimer's disease (AD) is the most common neurodegenerative disease that causes dementia. Olfactory dysfunction is detected at preclinical stage of this disease, this is important for the early appointment of therapy. The smell identifcation process involves the olfactory and orbitofrontal cortex, mediobasal structures of the temporal region, including the entorhinal cortex and hippocampus, which makes it extremely sensitive to neurodegeneration, especially of the Alzheimer's type. In patients at risk of developing AD (for example, carriers of the APOE4 genotype), patients with mild cognitive impairment and subjective cognitive decline also have olfactory dysfunction, which increases with the progression of cognitive defcit. This article presents the proposed mechanisms of hyposmia development in patients with Alzheimer's disease, the main methods of its study, such as olfactory tests, evoked olfactory potential, MRI and functional MRI, as well as data from population studies of recent years.