Pseudo-coloured images showing capillary flow. Warmer colours correspond to higher flow. Flow appears qualitatively greatest in ES carrier

A pilot study at the Keck School of Medicine of the University of Southern California, USA, has demonstrated an association between increased retinal capillary blood flow and early-stage autosomal dominant Alzheimer's disease (ADAD). 

Optical coherence tomography angiography (OCT-A) was performed on the retinas of controls and patients carrying the PSEN1 or APP mutations responsible for ADAD. The ADAD patients were divided into early-stage (ES) or late-stage (LS) groups. While there was no significant difference in retinal capillary blood flow between control eyes and those of the LS group, the ES group exhibited greater flow than the controls or LS group. Researchers led by Dr Maxwell Singer said that these findings support their hypothesis that increased perfusion is a pathophysiologic feature of presymptomatic stages of ADAD. 

“It is noteworthy that there are several published findings of decreased retinal capillary density in subjects with late onset Alzheimer’s disease (LOAD). These studies generally describe lower retinal capillary density measures among symptomatic LOAD subjects but not subjects with earlier stages of disease or mild cognitive impairment. These studies tend to support the idea that changes in capillary density, if present, occur later in the course of LOAD,” said researchers. 

For more on the eye’s relationship with Alzheimer’s, see https://eyeonoptics.co.nz/articlesearchresults?searchstring=alzheimer%27s