Association between retinal markers and cognition in older adults: a systematic review

Abstract

ObjectivesTo appraise the existing literature reporting an association between retinal markers and cognitive impairment in adults aged 65 years and over and to provide directions for future use of retinal scanning as a potential tool for dementia diagnosis.DesignSystematic review of peer-reviewed empirical articles investigating the association of retinal markers in assessing cognitive impairment.Data sourcesThree electronic databases, Medline, PsycINFO and EMBASE were searched from inception until March 2022.Eligibility criteriaAll empirical articles in English investigating the association between retinal markers and cognition in humans aged ≥65 years using various retinal scanning methodologies were included. Studies with no explicit evaluation of retinal scanning and cognitive outcomes were excluded. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool.Data extraction and synthesisData extraction was conducted by two authors (VJ, RS) and reviewed by another author (JS). Results were synthesised and described narratively.ResultsSixty-seven eligible studies examining 6815 older adults were included. Majority of studies were cross-sectional (n=60; 89.6%). Optical coherence tomography (OCT) was the most commonly used retinal scanning methodology to measure the thickness of retinal nerve fibre layer, the ganglion cell complex, choroid and macula. 51.1% of cross-sectional studies using OCT reported an association between the thinning of at least one retinal parameter and poor cognition. Longitudinal studies (n=6) using OCT also mostly identified significant reductions in retinal nerve fibre layer thickness with cognitive decline. Study quality was overall moderate.ConclusionRetinal nerve fibre layer thickness is linked with cognitive performance and therefore may have the potential to detect cognitive impairment in older adults. Further longitudinal studies are required to validate our synthesis and understand underlying mechanisms before recommending implementation of OCT as a dementia screening tool in clinical practice.PROSPERO registration numberCRD42020176757.

Association of retinal thickness and microvasculature with cognitive performance and brain volumes in elderly adults

“…MoCA, as a general cognitive screening tool, correlated with RNFL thickness in our study. Previous reports (Oktem et al, 2015;Liu et al, 2019;Jeevakumar et al, 2022) have shown a significant correlation between OCT parameters and MoCA scores. Our findings suggest that thinner RNFL may indicate reduced MoCA scores which are in line with previous reports.…”

Association of retinal nerve layers thickness and brain imaging in healthy young subjects from the i‐Share‐Bordeaux study

“…On the other hand, studies exploring the associations between retinal layers and cognitive function in young populations are very scarce. Indeed, the previous studies that have explored these associations were mainly conducted among adults (over 40 years) (Girbardt et al, 2021; Jeevakumar et al, 2022; Khawaja et al, 2016; Ko et al, 2018; Merten et al, 2020). To our knowledge, only one previous study in this field has included young people, showing that retinal layer thickness assessed in middle age was associated with cognitive performance in childhood and adulthood (Barrett‐Young et al, 2022).…”

“…On the other hand, studies exploring the associations between retinal layers and cognitive function in young populations are very scarce. Indeed, the previous studies that have explored these associations were mainly conducted among adults (over 40 years) (Girbardt et al, 2021;Jeevakumar et al, 2022;Khawaja et al, 2016;Ko et al, 2018;Merten et al, 2020).…”

The Eye as a Diagnostic Tool for Alzheimer’s Disease

“…Numerous studies have demonstrated that individuals with AD possess considerably thinner retinas than both healthy controls and individuals with mild cognitive impairment [ 32 , 33 , 34 ]. The literature consistently describes thinning of the peripapillary retinal nerve fiber layer (RNFL) and the ganglion cell–inner plexiform layer complex (GC-IPL), along with a reduction in total macular volume in patients with AD [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. A 2017 meta-analysis by den Haan et al reviewed 25 studies analyzing retinal thickness in AD, mild cognitive impairment (MCI) patients and healthy controls (HCs).…”