Retinal microvascular impairment prior to ganglion cell loss in mild cognitive impairment and Alzheimer’s disease

Abstract

Purpose : To determine the retinal microvascular network alterations in mild cognitive impairment (MCI) and Alzheimer’s disease (AD).

Methods : Optical coherence tomography angiography (OCTA) with Cirrus Angioplex^TM (Carl Zeiss Meditec, Dublin, CA) was used to image the retinal microvascular network at the macular region. Fractal analysis (box counting, D_box) representing vessel density in superficial and deep plexuses and retinal microvascular network was performed in different annular and quadrantal zones. In addition, macular ganglion cell-inner plexiform layer (GCIPL) thickness was measured. Microvascular dysfunction was compared between 3 groups of participants, twelve AD patients, 20 MCI patients and 21 normal subjects with a similar age range.

Results : AD patients had lower vascular densities in the temporal quadrant of the retinal vascular network and an annulus from 0.92 to 1.08 mm in the deep vascular plexus (P < 0.05) compared to controls. MCI patients in comparison to controls had lower vascular densities of the superficial and deeper vascular plexuses in the annulus (0.6 to 2.5 mm) (P < 0.05). In AD patients, the vascular density in the deep vascular plexus was related to GCIPL thickness (r = 0.82, P < 0.05). Both retinal and superficial vascular network densities were negatively correlated to disease duration (r = -0.58 for the retinal vascular network and r = -0.65 for the superficial vascular plexus, both P < 0.05). However, none of vascular densities in AD was significantly related to Mini-Mental State Examination (MMSE). In MCI patients, the density in the superficial vascular plexus was related to GCIPL thickness (r = 0.45, P < 0.05) but not to MMSE or disease duration.

Conclusions : To our knowledge, this is the first study showing impaired retinal microvascular network in MCI and AD patients, which was related to GCIPL thickness, prior to GCIPL thinning. The alteration of vascular density in AD patients is related to disease duration and may indicate progressive loss of retinal microvascular network during disease progression.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.