May Imaging Eye Give Early Clues to Alzheimer's

CHICAGO – Changes in the retinal vasculature may identify patients in the earliest stages of Alzheimer's disease.

One study showed that patients with Alzheimer's disease had significantly reduced macular vessel density (VD) and perfusion density (PD) as compared to patients who had mild cognitive impairment (MCI) and a group of healthy volunteers. The second study, involving participants in an Israeli registry of familial Alzheimer's disease, showed badociations between brain-scan results, cognitive function, and retinal vasculature in asymptomatic individuals with a family history of Alzheimer's disease.

Both studies involved the use of optical coherence tomography (OCT) to study changes in retinal blood vessels. The findings add to previous evidence badociations between retinal changes and Alzheimer's disease, reported at the American Academy of Ophthalmology meeting.

"Changes in the retinal microvasculature may mirror small-vessel cerebrovascular changes in Alzheimer's disease," Sharon Fekrat, MD, of Duke University Medical Center in Durham, North Carolina, and colleagues in a poster presentation. "These parameters may be used to predict noninvasive biomarkers for the diagnosis of Alzheimer's disease.

Previous studies demonstrated badociations between changes in retinal microvasculature and Alzheimer's disease. Authors of one review that "retinal microvascular abnormalities can offer an important window on the brain for etiological studies." OCT angiography (OCTA) showed retinal vascular abnormalities and altered retinal architecture in patients with normal cognition but preclinical.

Fekrat and colleagues noted that OCTA-detected vascular remodeling is more commonly recognized in badociation with patients with MCI and Alzheimer's disease. To continue the line of investigation, they conducted a cross-sectional study involving 39 patients with Alzheimer's disease, 37 with MCI, and 133 healthy individuals ages ≥50.

In most cases, OCTA was performed. Additionally, all study participants had cognitive badessments by means of a validated questionnaire. The primary objective was to evaluate retinal microvasculature in the superficial capillary plexus (SCP) and comparative findings in the three groups of study participants.

The primary outcome was VD and PD in the SCP, as defined by Early Treatment Diabetic Retinopathy Study (ETDRS) criteria.

The results showed that patients with Alzheimer's disease had significantly reduced VD and PD in both the ETDRS 3-mm circle and ETDRS 3-mm ring as compared with the healthy control group.P= 0.015 to P= 0.004). The Alzheimer's group also had a significant reduction in the incidence ofP= 0.041 to P= 0.004).

The same measures were significantly reduced in the Alzheimer's subgroup compared with the MCI subgroup (P= 0.004 to P= 0.001). Additionally, the Alzheimer's subgroup had significantly reduced VD in the 6-mm circle (P= 0.047) and a trend vs. reduced PD (P= 0.053).

The patients with MCI differed from the control group with respect to temporal retinal nerve fiber layer, which was significantly reduced in the former group (P= 0.04).

The Israeli study involved 195 participants in the Israel Registry of Alzheimer's Prevention; 138 had parents with Alzheimer's disease and 57 age-matched controls had parents without Alzheimer's disease. None of the offspring participants had symptoms of Alzheimer's disease.

The primary objective was to identify early retinal biomarkers for Alzheimer's disease, said Ygal Rotenstreich, MD, of Sheba Medical Center in Tel Hashomer in Israel.

The participants underwent retinal badessment by spectral domain OCT, cognitive badessments of executive function and episodic memory, and brain MRI. Results showed that patients with a history of Alzheimer's disease had increased volume, which was badociated with thicker macular inner layers (P= 0.028 to P= 0.003). Additionally, better management is badociated with increasedP= 0.007 for total macular thickness). No significant badociations exist in the control group for any of the retinal measurements.

"The badociations between macular thickness, performance in memory, and hippocampal volumes are measurable in yet-asymptomatic subjects at risk for Alzheimer's disease," Rotenstreich's group concludes a poster presentation. "Observations regarding different levels of retina – rather than the entire retinal thickness – may provide added sensitivity and specificity in the prediction of Alzheimer's disease."

2018-10-31T16: 00: 00-0400