A study conducted in Shanghai used OCT angiography (OCT-A) to determine that patients with Alzheimer’s disease exhibited significant differences in their macular vasculature compared with healthy controls.

Because the microvascular density in the innermost circle of the deep retinal capillary plexuses was significantly lower in patients with mild cognitive impairment, the researchers believe the vasculature density could be reduced before the appearance of the clinical signs of Alzheimer’s.

The researchers used OCT-A to examine 21 healthy control patients (33 eyes), 21 patients with mild cognitive impairment (32 eyes) and 18 patients with Alzheimer's disease (28 eyes).

The microvascular densities of the deep retinal capillary plexuses at all quadrants of the parafovea and perifovea were significantly lower in Alzheimer’s disease patients compared with the control group. The mild cognitive impairment patients showed significant microvascular loss in most sectors of the parafovea and the superior external sector of the deep retinal capillary plexuses but not in the parafovea or perifovea of the superficial retinal capillary plexuses.

The study found no significant difference in microvascular density of the superficial retinal capillary plexuses among the groups, except at the superior inner sector between the Alzheimer’s and control groups.

“The increase in the magnitude of density differences from the central to outer annular zones in the deep retinal capillary plexuses is likely related to the cognitive decline while the disease progress,” the researchers wrote in their paper on the study. “This result suggests that the parafoveal annular zone might be a good biomarker for detecting and monitoring the early cognitive changes of Alzheimer’s disease.”