Could low reflective drusen indicate cognitive status?

Abstract

Purpose : In addition to the higher prevalence of cogntive impairment among those with Age-related Macular Degeneration (AMD), b-amyloid, best known as a component of the senile plaques in Alzheimer’s disease (AD), has also been identified as a component of drusen. However, not all drusen contain the protein. The reflectivity of drusen on optical coherence tomography (OCT) is indicative of its contents. This study aims to determine if there is a link between drusen reflectivity and cognitive staus.

Methods : Participants with AMD were recruited from the Concordia Database of Retinal Images. Drusen from OCT raster scans was categorized as low, medium, or high reflectivity based on previous literature. Retinas were classified as having the characteristic present if at least 5 drusen with the same reflectivity were identified. Cognitive status was measured using the Montreal Cognitive Assessment (MoCA), which was scored according to the original instructions and the blind version (MoCAB). The Memory Index Score (MIS) was also calculated. The Visual Function Index-12 (VF-12) was used to indicate degree of difficulty with activities of daily living.

Results : At present, 26 participants (5M, 21F) ranging in age from 68 to 100 met the criteria. Bilateral low reflective drusen were identified in 8 individuals. Cognitive scores significantly differed between groups with those having low reflective drusen performing better on the MoCA (U= 32.0, p= 0.049, d = -0.885) and MoCAB (U = 29.0, p = 0.031, d = -1.015). The MIS showed that individuals with no low reflective drusen were at higher risk of converting to AD in the next year (U= 12.0, p= 0.004, d= -1.290). Those with low reflective drusen had significantly more difficulty with day-to-day activities according to the VF-12 (U= 37, p=0.030, d= -1.020). These groups did not significantly differ by age, binocular visual acuity or duration of AMD (all: p> 0.05).

Conclusions : Data collection is ongoing; an a priori power analysis recommends 62 individuals per group (present v. absent). However, Cohen’s d alreadyindicates a large effect. It appears that despite having greater difficulty with activities of daily living, individuals with low reflective drusen have better cognitive performance. Lipids are known to present optically inactive on OCT. This suggests low reflective drusen may be lipid-based and not contain b-amyloid. Further study in the correlation of histopathology and OCT findings will be required.

This is a 2020 ARVO Annual Meeting abstract.