A peek at the window from the eye into the brain: potential use of OCT angiography in dementia

Dementia is defined as the irreversible deterioration of acquired cognitive abilities (executive functions, memory, language, visuospatial, and motor) because of progressive neurodegeneration. According to a report by the World Health Organization (WHO) in 2018, dementia ranks as the 7 most common worldwide cause of death. In 2018, the globally estimated number of people afflicted by dementia was 50 million, a figure which is expected to triple by the year 2050 [1]. The worldwide rapidly aging population and the resultant unprecedented rise in the incidence of dementia are anticipated to cause a greater burden in health expenditures both in underdeveloped and developed countries alike. Optical coherence tomography angiography (OCT-A) is a noninvasive and facile method for visualizing retinal and choroidal microcirculation obviating the need for administering a systemic contrast agent. Compared to other brain imaging modalities, such as positron emission tomography imaging, it is more cost-effective and rapidly allows layer-bylayer assessment of retinochoroidal microcirculation. In a routine retina clinic, OCT-A is mainly employed for the diagnosis and monitoring of age-related macular degeneration and diabetic retinopathy. It has also become a popular research tool for assessing peripapillary and macular microcirculation in glaucoma and other optic neuropathies with the hope of finding various vascular cues that may enable earlier disease diagnosis and/or the detection of its progression [2]. In addition to its indispensable role in a busy ophthalmology clinic, studies have shown that OCT-A may potentially be a highly useful ancillary tool in various other non-ophthalmic diseases that directly or indirectly impact retinal and/or choriocapillaris microcirculation, such as multiple sclerosis, Parkinson’s, and Alzheimer’s diseases [3].